IOS on Lantean

iOS Simulator Logs

Sat, 19 May 2018 14:51:23 +0000

Leaving this link here… because… i kinda always forget the path!

~/Library/Logs/CoreSimulator/

Swift: Type Casting in For Loop

Wed, 27 Dec 2017 11:55:30 +0000

Okay. I need to jot this down somewhere, because i find myself googling this snippet, at least once a month. It’s not complex, but for some reason, it’s constantly slipping off my mind!

for case let children as ElementNode in rootNode.children { }

LLDB + Xcode 8 Kung Fu

Tue, 14 Mar 2017 10:34:54 +0000

Printing Arrays

parray number pointer
poarray number pointer

Reading Method Parameters

register read $arg1 $arg2
memory read $arg1

Printing Objects in Swift

expr -O --language objc -- 0x1003183e0

Disassembling the current frame

disassemble --frame

Module Image

image list ModuleName

Fixing Xcode 8's Code Completion

Mon, 23 Jan 2017 17:32:41 +0000

Open Preferences > Text Editing
Uncheck Enable Type-Over Completions
Be Happy!

Profiling: Swift Compile Time

Thu, 06 Oct 2016 19:04:00 +0000

xcodebuild -scheme TARGET clean build OTHER_SWIFT_FLAGS="-Xfrontend -debug-time-function-bodies" | grep .[0-9]ms | grep -v ^0.[0-9]ms | sort -nr > culprits.txt

Reference Here

Xcode 8: Disabling Networking Logs

Sat, 17 Sep 2016 18:27:25 +0000

Xcode 8 seems to be printing, for whatever reason, lots and lots of extra debug information. We can shut it down by means of an environment variable:

OS_ACTIVITY_MODE = disable

Reference Here

UITextView + Intrinsic Content Size

Mon, 29 Aug 2016 11:19:14 +0000

Note to future self: the trick to get intrinsicContentSize to properly work, in UITextView instances, is to simply disable scrolling in the UITextView instance.

That way… the intrinsic size will be properly calculated.

Using Xcode 7.x with an iOS 10 Device

Thu, 16 Jun 2016 16:17:45 +0000

Trick of the month….

Upgrade your device to iOS 10
Install Xcode 8 (Beta)
Hook up your device and launch Xcode. It’ll download debugging symbols.
Run this command in bash:

sudo ln -s /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/10.0\ (14A5261u) /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/10.0\ (14A5261u)

And now you can use your iOS 10 device with Xcode 7. Phew

ARC: weakSelf Caveats

Mon, 16 Nov 2015 12:13:40 +0000

Here’s an interesting ARC scenario. Consider the following snippet:

__weak __typeof(self) weakSelf = self;
int64_t delay = (int64_t)(0.1 * NSEC_PER_SEC);
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, delay), dispatch_get_main_queue(), ^{
 [weakSelf doSomething];
});

Whenever the block gets executed… weakSelf might have a valid reference, or not. Right?. Now, what happens with the following snippet?

__weak __typeof(self) weakSelf = self;
int64_t delay = (int64_t)(0.1 * NSEC_PER_SEC);
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, delay), dispatch_get_main_queue(), ^{
 [weakSelf doSomething];
 [weakSelf doSomethingElse];
});

This is where it gets interesting!. There’s a possibility that doSomething might get executed, while doSomethingElse might not.

Swift: Unit Testing

Fri, 24 Jul 2015 16:50:49 +0000

I’ve recently stumbled upon severe issues, while trying to write a Unit Test, in Swift, that would access Swift Code that belongs to the main app.

Contrary to what ~~almost~~ everyone mentions, you should not import the Main App’s files into the Testing target.

Instead, this is what you should do:

Enable Defines Module in the main target.
Add an import at the top of the Unit Test, to make the main project visible.
Make sure that the classes to be tested are set to public.

Reference Here!

Debugging Autolayout

Thu, 11 Dec 2014 12:06:37 +0000

If you need to debug the constraints that produced any view layout, just hit LLVM, and type:

po [[UIWindow keyWindow] _autolayoutTrace]

This will help you get the Autolayout Trace. Pick up the troublesome view, find its memory address, and then try:

po [0x12341234 constraintsAffectingLayoutForAxis:1]

Note that you should replace 0x12341234 with the memory address of the view you’d like to debug. AxisX = 0, while AxisY = 1.

Props to this extremely useful post.

iOS 8 Autosizing Cells

Thu, 11 Dec 2014 09:42:44 +0000

The latest iOS release (8.0 at the time this was written!) added a new cool feature: autosizing cells. Meaning that we don’t really need to implement tableView:heightForRowAtIndexPath: anymore.

How can we enable this?. Super simple, just add the following snippet:

self.tableView.estimatedRowHeight = SomeConstant;
self.tableView.rowHeight = UITableViewAutomaticDimension;

Now, here’s the deal. iOS 7 still requires tableView:heightForRowAtIndexPath: to be implemented. And if you do implement it, iOS 8 will disregard the Automatic Dimension settings.

Solution?.. import objc/runtime.h, and place this hack in your UITableView’s delegate:

Fixing: StatusBar covering your UIViewController's view

Fri, 31 Oct 2014 18:52:48 +0000

Ever since iOS 7, if you’re not using a UINavigationController instance, you’ll need to perform a very simple step, in order to prevent iOS’s StatusBar from covering your view:

Press Control, click over the “Top Layout Guide”, and drag it upon the troublesome view.
You’ll get a small popup. Please, click on “Vertical Spacing”.
Edit the new constraint, and update the Constant value, as needed.

Reference here!

CoreData HeavyWeight Migration Issues

Sat, 25 Oct 2014 10:45:36 +0000

We recently hit a pretty severe bug. In one of our apps, users began experiencing token issues after an upgrade.

Bottomline?… the last upgrade had a Heavyweight migration. So far so good, but what happened?. Turns out that the URIRepresentation that can be used to map a NSManagedObjectID, is and is not reliable. Everything is okay, until you perform a heavyweight migration!.

Heavyweight migrations might swizzle your NSManagedObjectID’s. Fix?, create your own primaryKeys. NSUUID helper class is the easiest way to accomplish that.

TextKit + iOS Clipping Bug

Fri, 15 Aug 2014 01:06:15 +0000

I’ve just spent several hours hunting an iOS 8 specific bug. After inserting several new lines into a UITextView (with custom TextKit stack), the newly-added text would not appear.

This is the way our NSTextContainer instance was being initialized

@implementation MyTextView
- (instancetype)init {
 SPInteractiveTextStorage *textStorage = [[MyInteractiveTextStorage alloc] init];
 NSLayoutManager *layoutManager = [[NSLayoutManager alloc] init];

 NSTextContainer *container = [[NSTextContainer alloc] initWithSize:CGSizeMake(0, CGFLOAT_MAX)];
 container.widthTracksTextView = YES;
 container.heightTracksTextView = YES;

 [layoutManager addTextContainer:container];
 [textStorage addLayoutManager:layoutManager];

 self = [super initWithFrame:CGRectZero textContainer:container];
// ...

Now, the interesting part is, specifically, heightTracksTextView = YES.

Debugging UIKit Usage on BG Threads

Thu, 10 Jul 2014 17:08:38 +0000

Based on this awesome cocoanetics post, and updated to work with JRSwizzle, you might find the UIView+Debug category very handy, specially when debugging die hard bugs.

#import "JRSwizzle.h"

@interface UIView (Debug)

@end

@implementation UIView (Debug)

- (void)methodCalledNotFromMainQueue:(NSString *)methodName
{
 NSLog(@"-[%@ %@] being called on background queue. Break on -[UIView methodCalledNotFromMainQueue:] to find out where", NSStringFromClass([self class]), methodName);
}

- (void)_setNeedsLayout_MainQueueCheck
{
 if (![NSThread isMainThread])
 {
 [self methodCalledNotFromMainQueue:NSStringFromSelector(_cmd)];
 }
 
 // not really an endless loop, this calls the original
 [self _setNeedsLayout_MainQueueCheck];
}

- (void)_setNeedsDisplay_MainQueueCheck
{
 if (![NSThread isMainThread])
 {
 [self methodCalledNotFromMainQueue:NSStringFromSelector(_cmd)];
 }
 
 // not really an endless loop, this calls the original
 [self _setNeedsDisplay_MainQueueCheck];
}

- (void)_setNeedsDisplayInRect_MainQueueCheck:(CGRect)rect
{
 if (![NSThread isMainThread])
 {
 [self methodCalledNotFromMainQueue:NSStringFromSelector(_cmd)];
 }
 
 // not really an endless loop, this calls the original
 [self _setNeedsDisplayInRect_MainQueueCheck:rect];
}

+ (void)toggleViewMainQueueChecking
{
 NSError *error = nil;
 [UIView jr_swizzleMethod:@selector(setNeedsLayout)
 withMethod:@selector(_setNeedsLayout_MainQueueCheck)
 error:&error];
 
 [UIView jr_swizzleMethod:@selector(setNeedsDisplay)
 withMethod:@selector(_setNeedsDisplay_MainQueueCheck)
 error:&error];
 
 [UIView jr_swizzleMethod:@selector(setNeedsDisplayInRect:)
 withMethod:@selector(_setNeedsDisplayInRect_MainQueueCheck:)
 error:&error];
}

@end

Loading SecCertificateRef from PEM String

Mon, 07 Jul 2014 17:05:49 +0000

In order to load a PEM certificate, you’d probably wanna grab the PEM itself from your backend, right?.

You can do so, by means of this command:

openssl s_client -showcerts -host host.com -port 443

Once you’ve got the certificate, you should get rid of the Begin/End Certificate substrings.

Cocoa Snippet itself is quite easy:

NSData *rawCertificate = [[NSData alloc] initWithBase64Encoding:PlaintextCertificateString];
SecCertificateRef parsedCertificate = SecCertificateCreateWithData(NULL, (__bridge CFDataRef)rawCertificate);

That’s it. Don’t forget about checking expiration dates. Unfortunately, Apple’s API to do so is private, and i personally refuse to build OpenSSL into my app, just to check that.

Pushing a new CocoaPods Version with Trunk

Mon, 30 Jun 2014 12:15:04 +0000

CocoaPods is a useful dependency management tool for OSX and iOS. They’ve recently introduced some changes, to ease the process of publishing new versions of your Framework.

Just in case you’re lost, just like me, these are the commands required to push a new release:

pod trunk register EMAIL@HERE.COM 'Your Name' --description='MBP 15'
pod trunk me
pod trunk push FrameworkName.podspec.json

Note that after hitting trunk register, you’ll get an email to confirm your identity.

Codesign Check

Thu, 26 Jun 2014 10:38:28 +0000

Keychain access for iOS apps is tied up to the provisioning profile you use to sign the binary. So, what happens if you release a new build, signed using a different provisioning profile?.

Yes! your guess is accurate!. You loose access to anything you’ve stored in the keychain, resulting in (probably) deauthentication.

There is a command that allows you to verify the “Keychain Access Group” for a given executable. By means of this, you’ll be able to verify if your new release will have the same access than your previous build (assuming you also have that binary!).

Repairing CocoaPods Broken Repository

Tue, 04 Feb 2014 16:02:32 +0000

It seems that CocoaPods fellows had an issue with libgit, and their public repository broke down.

In order to fix it, you’ll need to….

pod repo remove master
pod setup

Generating a Mac Iconset

Wed, 24 Jul 2013 21:06:24 +0000

You’ll need to create PNG assets with the following sizes and filenames:

icon_16x16.png
icon_16x16@2x.png
icon_32x32.png
icon_32x32@2x.png
icon_128x128.png
icon_128x128@2x.png
icon_256x256.png
icon_256x256@2x.png
icon_512x512.png
icon_512x512@2x.png

All of those assets should go into a folder named ‘Icon.iconset’. Afterwards, just fire Terminal and type the following command:

iconutil -c icns

If all went well, you should have a .icns file right there!.

Reference: Apple’s Guidelines.

Waiting until two async blocks are executed (Version #2)

Wed, 26 Jun 2013 15:58:10 +0000

This is a nice variant to this other post. It gives you… way too much flexibility!

dispatch_group_t group = dispatch_group_create();

dispatch_group_enter(group);
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
 NSLog(@"Block1");
 [NSThread sleepForTimeInterval:5.0];
 dispatch_group_leave(group);
 NSLog(@"Block1 End");
});

dispatch_group_enter(group);
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
 NSLog(@"Block2");
 [NSThread sleepForTimeInterval:8.0];
 dispatch_group_leave(group);
 NSLog(@"Block2 End");
});

dispatch_group_notify(group, dispatch_get_main_queue(), ^ {
 NSLog(@"Group Notify Block3 :: %d", [NSThread isMainThread]);
});

Waiting until two async blocks are executed

Tue, 09 Apr 2013 22:42:33 +0000

The following snippet of code.. which is super interesting, is based on this post. This allows to dispatch a block, on Main Thread, once two async operations are completed.

dispatch_group_t group = dispatch_group_create();

dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
 NSLog(@"Block1");
 [NSThread sleepForTimeInterval:5.0];
 NSLog(@"Block1 End");
});

dispatch_group_async(group, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^ {
 NSLog(@"Block2");
 [NSThread sleepForTimeInterval:8.0];
 NSLog(@"Block2 End");
});

dispatch_group_notify(group, dispatch_get_main_queue(), ^ {
 NSLog(@"Block3 :: %d", [NSThread isMainThread]);
});

dispatch_release(group);

New iPhone Jailbreak Released

Wed, 06 Feb 2013 21:52:30 +0000

It's been a while since the last iPhone jailbreak was made public. But all evil comes to an end, sooner rather than later. A couple days ago, a hacking group named evad3rs, published a brand new Jailbreak tool for iOS 6.x.

It’s claimed to be able to jailbreak any iOS device: iPod / iPad / iPhone / iPad Mini. I’ve tested it myself on two devices: iPhone 4s and iPhone 5. The results were impressive. They managed to combine at least 3 different exploits to make things work.

Checking the UUID of a DSYM file

Tue, 05 Feb 2013 12:43:35 +0000

So… you’ve got a crashlog, and you don’t know if a given DSYM actually matches with the original executable?. Well, there is a super easy way to verify this. Simply type the following, in your console:

dwarfdump -u Project.app.dSYM/Contents/Resources/DWARF/Project

Ideally, mdfind should help you locate the matching DWARF. But sometimes… symbolication requires extra debugging.

Xcode 4.6 Released!

Tue, 29 Jan 2013 20:47:08 +0000

Head your browsers to Apple’s Development Center. Apple has just released Xcode 4.6, with iOS 6.1 support (Release!).

So far it has proven to be sooooo much stable. The previous release was a nightmare, specially during summertime. (Those of you who run Xcode on macbooks understand me… the entire machine turns into an iron!).

However, i’ve been reading quite a lot of reports, from many different sources, pointing out that although 4.6 freezes less, it still has a couple of severe bugs, that will lower your productivity.

Fixing 'Could Not Read from Device' Xcode Error

Mon, 28 Jan 2013 15:04:51 +0000

Did you just get this error while trying to run your app in Xcode?…

The fix is fairly simple. Simply launch iTunes, make sure the device is plugged in, and synchronize. The error should be gone by now.

Told you, it was a quick fix!

Knowing Memory Usage in iOS

Mon, 28 Jan 2013 14:55:41 +0000

This task is quite straightforward. First, import the following headers:

#import <mach/mach.h>
#import <mach/mach_host.h>

Now what?. Simple… use this method:

-(void)printMemoryUsage
{
 mach_port_t host_port;
 mach_msg_type_number_t host_size;
 vm_size_t pagesize;

 host_port = mach_host_self();
 host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
 host_page_size(host_port, &pagesize);

 vm_statistics_data_t vm_stat;

 if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS)
 {
 NSLog(@"Failed to fetch vm statistics");
 }

 /* Stats in bytes */
 natural_t mem_used = (vm_stat.active_count +
 vm_stat.inactive_count +
 vm_stat.wire_count) * pagesize;
 natural_t mem_free = vm_stat.free_count * pagesize;
 natural_t mem_total = mem_used + mem_free;

 NSLog(@"used: %u free: %u total: %u", mem_used, mem_free, mem_total);
}

Credits: This is a snippet taken from this Stackoverflow question.

Free iPhone MAME Emulator

Sun, 27 Jan 2013 11:35:22 +0000

From time to time, Apple’s Review Team, for whatever reason, allows Apps that clearly violate the AppStore guidelines.

This time, Gridlee managed to got in. It’s free, and it’s somewhere around 85 megabytes. You can expect it to be removed sooner rather than later… so my recommendation would be… go and get it!.

You can install any ROMs you might have already downloaded. Playing Choplifter on an iPad Retina isn’t hi-tech, but i’ve always said, old school games are the best. You don’t need complex 3d algorithms, shadows, or near-perfect water effects to have fun.

New iPhone Jailbreak!

Sun, 27 Jan 2013 11:26:43 +0000

Today, a new iPhone Jailbreak solution, has been announced to be already on its way. iOS 6.0 and 6.1 beta 4 have been both jailbroken, and the team is waiting for iOS 6.1 final release to launch the goodies!.

If you have a previous iOS version, and you still wanna jailbreak your device, you should head to this site. They have a nice archive of every JB solution that got released.

Top 5 iPhone Games

Fri, 25 Jan 2013 21:58:23 +0000

Do you usually spend time waiting for a bus… without anything to do?. And how about when there is nothing on TV? what do you do?. Or… say… you’ve just finished that book you’ve been reading for months, and you have no clue what to do with your spare time!.

If you answer ‘yes’ to any of the above questions, then this short list of Top 5 iPhone Games is just for you!.

Using NSLocalizedString with a dictionary stored inside a bundle

Wed, 16 Jan 2013 20:29:52 +0000

We’ve seen before how to create an iOS Assets bundle. Today, we’ll try to localize a string, using a dictionary stored in a bundle. In order to do so… we’ll rely on the following helper method:

@interface LABundles
+ (NSBundle*)someResourcesLocalizationBundle
@end

@implementation LABundles
+ (NSBundle*)someResourcesLocalizationBundle
{
	static NSBundle* someResourcesLocalizationBundle = nil;

	if ( someResourcesLocalizationBundle == nil )
	{
	 // This double check increases efficiency. Don't you get bored of asking the same thing twice?.
 @synchronized(self)
 {
 if ( someResourcesLocalizationBundle == nil )
 {
	 // Figure out the current language.
 		NSUserDefaults* defs = [NSUserDefaults standardUserDefaults];
 NSArray* languages = [defs objectForKey:@"AppleLanguages"];

 NSString* currentLanguage = [languages objectAtIndex:0];

	 // Map the current language's folder within the bundle
 NSBundle* bundle = [NSBundle someResourcesBundle];
 NSString* path = [bundle pathForResource:currentLanguage ofType:@"lproj"];

	 // Okay, let's go with the default bundle
 if ( path == nil )
 {
 someResourcesLocalizationBundle = bundle;
 }
	 // Bingo!
 else
 {
 someResourcesLocalizationBundle = [NSBundle bundleWithPath:path];
 }

 [someResourcesLocalizationBundle retain];
 }
 }
	}

 return someResourcesLocalizationBundle;
}
@end

What’s that all about?. Well… it turns out that order to resolve localized strings, first of all we need to figure out what’s the device’s language.

Loading UIImages from files stored inside a bundle

Wed, 16 Jan 2013 20:28:45 +0000

We’ve learnt before how to make an iOS Assets Bundle. In this mini post… we’ll learn how to learn images, stored in bundles. Okay.. this one is super simple:

UIImage* twitterBtnImage = [UIImage imageNamed:@"SomeResources.bundle/twitter-button.png"];

Of course, you need to have the ‘SomeResources’ bundle in your project. That’s it!

Loading NIBs stored inside a bundle

Wed, 16 Jan 2013 20:27:07 +0000

When does it make sense to store your NIBs inside a bundle?. As we’ve discussed before… this becomes handy when you’re distributing a framework which has some custom NIB files.

But wait…. how do you tell a UIViewController to load its nib file from a bundle?. Short answer… we’ll rely on UIViewController’s ‘initWithNibName: bundle:’ constructor.

Before doing that… we need to take care about a small detail, which is, how to load a NSBundle object (to pass on as the ‘bundle’ parameter).

Making an iOS Assets Bundle

Wed, 16 Jan 2013 20:16:41 +0000

An iOS Bundle is just a folder which contains resources. Roughly speaking, it allows you to store any resource you might need: images, nibs, or localized string files.

Why would you create an application bundle?. What’s that good for?.

Suppose you have a framework of your own. And… suppose that your framework has several UIViewController which require custom images. OR, suppose that you need to load different images dynamically, within your framework’s code.

Manually Symbolicating iOS Crashlogs

Wed, 16 Jan 2013 19:39:23 +0000

I’ve been facing this problem for as long as i’ve been developing iOS apps. What’s the deal with crashlogs????…..

Apple allows you to download crashlogs through iTunesConnect. What are crashlogs you may say. Well, crashlogs are simply text files that allows us to debug crashes. You get to see the Stack Dump at the moment of the crash, as well as the architecture, and loaded libraries.

What is symbolication??… well, the crashes you download in iTunesConnect aren’t useful, unless you’ve got the dSYM file matching that crashlog. If you do, you’ll be able to symbolicate it. That means that… instead of seeing memory addresses in the stack dump, you’ll get to see method and class names.

Adding support for iPhone 5 screens

Wed, 16 Jan 2013 18:18:20 +0000

Not long ago, i had to extend an app to support iPhone 5. Yes… iOS has autolayout functionality, that should aid the development of UIView’s.

But how about assets?. How do you load assets specially crafted for 568px height screens?. Furthermore.. how do you patch classes that inherit from UITableViewCell, to return dynamic height, according to the device?.

Simple!. By means of a super short UIScreen extension. The header should look like this…:

Calculating NSData's MD5

Wed, 16 Jan 2013 14:26:21 +0000

Suppose that you need to calculate a NSData’s MD5 signature.. for whatever reason. Say… you need to check the backend’s signature.

Well… simply add a NSData extension, with the following method:

- (NSString*)md5
{
 unsigned char result[16];
 CC_MD5( self.bytes, self.length, result ); // This is the md5 call
 return [NSString stringWithFormat:@"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
 result[0], result[1], result[2], result[3], 
 result[4], result[5], result[6], result[7],
 result[8], result[9], result[10], result[11],
 result[12], result[13], result[14], result[15]
 ]; 
}

Again, please, don’t you forget the imports!

Encrypting and Decrypting NSData with AES256

Wed, 16 Jan 2013 14:24:09 +0000

Today we’re gonna encrypt information, stored in a NSData object, using AES-256 algorithm. As you may already know, AES-256 is a symmetric encryption schema. Which means that you need to share, somehow, the key you’re gonna use (in order to decrypt the data).

I’ve encapsulated a couple helper methods, as a NSData extension, for the sake of simplicity. I’ve based myself on this. Let’s see…

- (NSData*)aes256EncryptWithKey:(NSString*)key
{
 // 'key' should be 32 bytes for AES256, will be null-padded otherwise
 char keyPtr[kCCKeySizeAES256 + 1];
 bzero( keyPtr, sizeof( keyPtr ) );

 // fetch key data
 [key getCString:keyPtr maxLength:sizeof( keyPtr ) encoding:NSUTF8StringEncoding];

 NSUInteger dataLength = [self length];

 // See the doc: For block ciphers, the output size will always be less than or equal to the input size plus the size of one block.
 // That's why we need to add the size of one block here
 size_t bufferSize = dataLength + kCCBlockSizeAES128;
 void *buffer = malloc( bufferSize );

 size_t numBytesEncrypted = 0;
 CCCryptorStatus cryptStatus = CCCrypt( kCCEncrypt, kCCAlgorithmAES128, kCCOptionPKCS7Padding,
 keyPtr, kCCKeySizeAES256,
 NULL /* initialization vector (optional) */,
 [self bytes], dataLength, /* input */
 buffer, bufferSize, /* output */
 &numBytesEncrypted );
 if( cryptStatus == kCCSuccess )
 {
 // The returned NSData takes ownership of the buffer and will free it on deallocation
 return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];
 }

 free( buffer );
 return nil;
}

And now… the decrypt routine…

Fixing WebKitLocalStorageDatabasePathPreferenceKey crash

Mon, 07 Jan 2013 15:46:53 +0000

I’ve been getting a lot of crashes with the following signature:

Exception Type: SIGABRT
Exception Codes: #0 at 0x351be32c
Crashed Thread: 0

Application Specific Information:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary setObject:forKey:]: attempt to insert nil value (key: WebKitLocalStorageDatabasePathPreferenceKey)'

What is this?. It’s pretty well explained here. My workaround?. Quite simple. Call this method as soon as your app launches:

-(void)fixWebkitCrash
{
 NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
 NSString* webkitPath = [defaults objectForKey:@"WebKitLocalStorageDatabasePathPreferenceKey"];
 NSString* bundlePath = [[[NSBundle mainBundle] bundlePath] stringByDeletingLastPathComponent];
 
 if([webkitPath containsString:bundlePath] == NO)
 {
 [defaults removeObjectForKey:@"WebKitLocalStorageDatabasePathPreferenceKey"];
 [defaults synchronize];
 }
}

Hopefully, this will save you a couple hours!.

Fixing "iTunes was unable to load dataclass” Error

Tue, 04 Dec 2012 13:34:15 +0000

I’ve been dealing with the “iTunes was unable to load dataclass” for several hours. I’ve uninstalled iTunes, Xcode, deleted the Mobile Device Support… reinstalled everything, booted the system, and nothing seemed to work.

After searching for quite some time, i’ve found this post. Long short story, if you delete this framework:

/System/Library/PrivateFrameworks/MobileDevice.framework

…and right afterwards you relaunch Xcode (which will, as a result, reinstall such framework)… you should be able to get rid of this… annoooooooooying problem.

UITableView Pull to Refresh

Sat, 24 Nov 2012 12:02:00 +0000

I know, i know. Apple’s iOS 6 introduces a new component (which is already available in the sdk)… that allows you to refresh a table whenever the user pulls it.

However… not everyone is targetting iOS 6 +… at least not yet. So, i’d like to share a link with you. Sam Vermette, a fellow with a couple public github repositories, did an excellent job writing an UIScrollView extension. It’s super easy to setup… clean, and most of all, self contained.

Resetting the Push Notifications Permissions Alert on iOS

Mon, 27 Aug 2012 19:11:45 +0000

I’m just pasting this from Apple’s Technical note… it’s soooo useful, yet, everytime i need to debug this, i spend at least 15 minutes with google…!.

The first time a push-enabled app registers for push notifications, iOS asks the user if they wish to receive notifications for that app. Once the user has responded to this alert it is not presented again unless the device is restored or the app has been uninstalled for at least a day.

If you want to simulate a first-time run of your app, you can leave the app uninstalled for a day. You can achieve the latter without actually waiting a day by setting the system clock forward a day or more, turning the device off completely, then turning the device back on.

Fixing 'Text in UITextField moves up after editing' glitch

Mon, 25 Jun 2012 17:44:36 +0000

I’ve recently come across this glitch in iOS: Text in UITextField moves up after editing (center while editing).

Long short story… when you end editing a textField, if you’re using a custom font, the text might move up. (If you get this glitch). Well, it turns out that this is a font specific problem… it’s not in your code.

So… how will we solve it?. TTX!. In this previous post we explained how to make TTX work in your 64 bit mac. So we’ll begin from there.

resignFirstResponder, the easy way!

Tue, 19 Jun 2012 17:08:05 +0000

If you have an UIControl in edit mode… but you have no idea which one is it… and you need to resignFirstResponder, there is an easy way to do this. No, you don’t need to hook to notifications. And you don’t need to find the firstResponder. This can be solved with just one call.

What you need to do is…

[_tableView endEditing:YES]

Note that you could have anything else rather than a _tableView. Easy. Right?

CoreAnimation: Bounce animation... like the Camera button

Thu, 14 Jun 2012 20:11:52 +0000

Have you seen the animation in which the lockscreen bounces… if you tap over the camera button?. Guess what!. That can be done, quite easily, with Core Animation.

We’ll implement this as an extension to UIView. So.. add a file named ‘UIView+CoreAnimation.h/m’, and paste the following code:

REF: Thanks to the Cocoanetics author for sharing this. I’ve tweaked his code just a little bit.

#import <QuartzCore/QuartzCore.h>

+ (CAKeyframeAnimation*)dockBounceAnimationWithViewHeight:(CGFloat)viewHeight
{
	NSUInteger const kNumFactors = 22;
	CGFloat const kFactorsPerSec = 30.0f;
	CGFloat const kFactorsMaxValue = 128.0f;
	CGFloat factors[kNumFactors] = {0, 60, 83, 100, 114, 124, 128, 128, 124, 114, 100, 83, 60, 32, 0, 0, 18, 28, 32, 28, 18, 0};

	NSMutableArray* transforms = [NSMutableArray array];

	for(NSUInteger i = 0; i < kNumFactors; i++)
	{
		CGFloat positionOffset = factors[i] / kFactorsMaxValue * viewHeight;
		CATransform3D transform = CATransform3DMakeTranslation(0.0f, -positionOffset, 0.0f);

		[transforms addObject:[NSValue valueWithCATransform3D:transform]];
	}

	CAKeyframeAnimation* animation = [CAKeyframeAnimation animationWithKeyPath:@"transform"];
	animation.repeatCount = 1;
	animation.duration = kNumFactors * 1.0f/kFactorsPerSec;
	animation.fillMode = kCAFillModeForwards;
	animation.values = transforms;
	animation.removedOnCompletion = YES; // final stage is equal to starting stage
	animation.autoreverses = NO;

	return animation;
}

- (void)jump
{
	CGFloat midHeight = self.frame.size.height * 0.5f;
	CAKeyframeAnimation* animation = [[self class] dockBounceAnimationWithViewHeight:midHeight];
	[self.layer addAnimation:animation forKey:@"bouncing"];
}

CoreGraphics: Drawing Dashed Lines

Wed, 13 Jun 2012 22:31:08 +0000

Suppose you wanna draw a dashed line all around a control. What should we do?. Well… simple. We need to invoke some CoreGraphics dark magic… it’s pretty self explanatory. The catch to it is that it’ll draw a dashed line. Play with it..!

static CGFloat const kDashedBorderWidth = (2.0f);
static CGFloat const kDashedPhase = (0.0f);
static CGFloat const kDashedLinesLength[] = {4.0f, 2.0f};
static size_t const kDashedCount = (2.0f);

- (void)drawRect:(CGRect)rect
{
 [super drawRect:rect];

 CGContextRef context = UIGraphicsGetCurrentContext();

 CGContextSetLineWidth(context, kDashedBorderWidth);
 CGContextSetStrokeColorWithColor(context, [UIColor grayColor].CGColor);

 CGContextSetLineDash(context, kDashedPhase, kDashedLinesLength, kDashedCount) ;

 CGContextAddRect(context, rect);
 CGContextStrokePath(context);
}

Current Selector's Name

Mon, 04 Jun 2012 16:07:11 +0000

So… suppose you wanna log the name of the ‘current’ method. You could hardcode the method name, right there… virtually everywhere… or you can do this:

NSLog(@"[ %@ ] did something", NSStringFromSelector(_cmd));

It’s simple. Yet, its something i didn’t know… three days ago!.

Twitter iOS SDK

Sat, 19 May 2012 11:49:08 +0000

I recently had to integrate one of my apps with Twitter. Let me say you something. I HATE TWITTER guys. Why?. Because everything is soooo complicated. Although there is a direct integration between Twitter and iOS 5, they have made it really hard for developers.

Why?. If you need to post tweets, backend side, you need to ask for ‘Reverse Auth’ permissions.. and it’s not something that can be done automatically. They have to personally approve this.

Fixing Bootstrap Errors

Wed, 09 May 2012 23:40:38 +0000

I’ve been having this error… A LOT…:

“Couldn’t register com.yourcompany.yourapp with the bootstrap server. Error: unknown error code. This generally means that another instance of this process was already running or is hung in the debugger.”

The bad side of this is that.. ps aux will not show anything useful. Thankfully, Mike Ash has solved this… i’m pasting below his script:

launchctl list|grep UIKitApplication|awk '{print $3}'|xargs launchctl remove

Source: Mike Ash Blog

Removing subviews that match any given criteria!

Wed, 09 May 2012 22:50:27 +0000

So… suppose that you have a container view. And for some reason, you need to remove the subviews that match any given criteria.

The straightforward solution would be to write a foreach loop, by hand, and remove the target subviews with a method call. Guess what!. There is a kung fu solution to this..!!. Check this out:

NSPredicate* predicate = [NSPredicate predicateWithFormat:@"self isKindOfClass: %@", [SomeView class]];
NSArray* viewsToRemove = [[self subviews] filteredArrayUsingPredicate:predicate];
[viewsToRemove makeObjectsPerformSelector:@selector(removeFromSuperview)];

Less code is better. Always.

Detecting taps in any UIView subclass

Wed, 09 May 2012 22:46:55 +0000

This one is a quick and easy trick. How do you detect taps in any UIView?. Simple. You need to use the UITapGestureRecognizer class… this way:

// Alloc the gesture recognizer
UITapGestureRecognizer* tapGestureRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(viewTapped)];
[tapGestureRecognizer setNumberOfTapsRequired:1];
[anyRandomView addGestureRecognizer:tapGestureRecognizer];
[anyRandomView setUserInteractionEnabled:YES];

[tapGestureRecognizer release];
tapGestureRecognizer = nil;

UILabel with Stroke!

Fri, 04 May 2012 20:40:29 +0000

Time to invoke some… dark magic. For some reason, UILabel doesn’t support stroke. So, if you’re… by chance… working on a videogame, or a simple iOS app, and you actually need to render an UILabel with a stroke, in a given color, you have come to the right place.

Let’s begin with the header file:

@interface LAStrokeLabel : UILabel
{
 NSUInteger _strokeWidth;
    UIColor* _strokeColor;
}

@property (nonatomic, assign) NSUInteger strokeWidth;
@property (nonatomic, retain) UIColor* strokeColor;

@end

So far so good… right?. Nothing weird. Just a simple UILabel subclass, with two extra properties.

Display a modal UIViewController when a UITabBarItem is pressed

Thu, 03 May 2012 17:54:13 +0000

Suppose the following scenario. You need to display a modal UIViewController whenever the user presses a specific button in a UITabBar.

The trick is pretty simple. First, add an empty UIViewController, wich will serve as placeholder for the ‘modal tab’:

UIViewController* someViewController    = [[UIViewController alloc] init];
[someViewController setTitle:NSLocalizedString(@"Modal Tab", nil)];
[someViewController.tabBarItem setImage:[UIImage imageNamed:@"modal.png"]];

Then, setup the UITabBarController’s delegate:

[_tabBarController setDelegate:self];

At last… you need to implement the UITabBarControllerDelegate protocol. Specifically, something that looks like this:

iOS and JavaScript Bridge

Sat, 21 Apr 2012 13:22:45 +0000

What if you need to write a completely dynamic app, and you need to have the ability of updating the App’s contents remotely, without the need of pushing a new build to the AppStore?.

What if you need to write javascript code, which needs to interact with your iOS code?. Yeah. I had that problem. Long short story, i’m testing a nice framework called clutch.

Clutch has a nice JavaScript and iOS SDK, which smoothens the interaction between those two technologies. When you ship the app, you bundle a version of the webApp in it.

Targetting iPhone 3gs and superior

Sat, 21 Apr 2012 12:36:16 +0000

I recently had a problem with one of the apps i’m working on. (Yeah, yet another problem!). The first release supported ARMv6 (which is handy when targetting older devices, as well, such as 1st and 2nd iPod generations, and the old iPhone 3g).

As it turns out, you cannot change the requirements of an app after pushing an update. I mean, you cannot simply remove ‘ARMv6’ support. Apple’s policy is that … you should continue supporting all of the target platforms you’ve enabled in the very first release.

GPS in Safari Mobile

Thu, 19 Apr 2012 10:46:25 +0000

So… what if you wanna get the GPS position, but within a WebApp’s context?. There are several tools, such as PhoneGap, that encapsulate GPS access. But it turns out that there is an extremely easy way to accomplish this task.

Check out this JavaScript snippet… easy, right?

navigator.geolocation.getCurrentPosition(foundLocation, noLocation);

function foundLocation(position)
{
 var lat = position.coords.latitude;
 var long = position.coords.longitude;
 alert('Found location: ' + lat + ', ' + long);
}

function noLocation()
{
 alert('Could not find location');
}

Debugging BAD_ACCESS crashes

Sun, 15 Apr 2012 23:26:15 +0000

Newbies can rely on ARC to handle memory management. But personally, i’d rather handling everything myself. Old school!.

Besides that, you’ll probably need to support iOS 4 devices, as well. So… at least for now, Memory Management is kind of a mandatory chapter, to everyone!.

So what happens when you get a ‘BAD_ACCESS’ crash?. There are just so many scenarios that can trigger that crash… but the most common is simply a message sent to a dealloc’ed object.

Using 'performSelector: withObject: afterDelay:'!

Sun, 15 Apr 2012 21:26:10 +0000

Sometimes, when developing an iOS application, we need to do something like ‘displaying a spinner’, and right after that, do a tedious task, such as query’ing a database, sorting a file, or hitting a backend.

As you may (or may not know)… all of the UIKit framework works on the Main Thread (with several exceptions, set aside). A common problem we might encounter is that… if you begin a long process after initializing an ActivityIndicatorView, the main thread will remain locked out, and thus… the spinner will never begin.

Preventing Paste in UITextField

Sun, 15 Apr 2012 19:43:39 +0000

Suppose that your app has a custom keyboard (or component) which populates an UITextField. So… suppose that you need to enable the User Interaction with that control. However, you don’t wanna anyone pasting values right there… because you wanna force the user to rely on your custom keyboard.

UITextField lacks a ‘disablePaste’ property. In order to do this, we’re gonna need to subclass UITextField. Our subclass should look like this…

UIView with Rounded Corners

Sun, 15 Apr 2012 19:33:42 +0000

Sooner rather than later, you’ll probably end up with a simple yet tricky requirement: an UIView with rounded corners.

iOS SDK has no ‘radius’ property. Ohhh wait!. Yeah, it actually has!. But the catch to it is that you need to import Quartz framework, first:

#import <QuartzCore/QuartzCore.h>

Also, you need to link the ‘QuartzCore.framework’. Otherwise the import won’t work.

So… how do you actually display an UIView with rounded corners?. Easy!

Removing Push Notifications from NotificationBar

Wed, 11 Apr 2012 12:24:03 +0000

I have come up with a weird problem…. which goes as follows:

The app receives a Push Notification.
You tap over the PN (in the iOS notification center).
The app gets launched… and you handle the notification
Problem: the notification remains in the ’notification bar'.

How do you clean it ?. Well… this isn’t in Apple’s docs. But i’ve figured out that if you execute the following line of code, the notification ‘gets acknowledged’:

JSON Parsers

Sun, 08 Apr 2012 22:41:21 +0000

XML days are numbered…. it’s just my opinion. I know, it’s out there in the wild, almost everywhere. But XML itself has a huge overhead, which is something we, as mobile software developers, really want to avoid.

Personally, i just love json. It’s extremely lightweight… and i dare to say, it is what XML should have been. Why is it exactly that you need to repeat a keyword once and over and over…???. I still don’t get what those guys were thinking… when they wrote the XML specs.

HTML Color to UIColor

Fri, 06 Apr 2012 14:30:03 +0000

This is a nice tool i’d like to share with you. While skinning your app, you might need to convert HTML color codes into those that are actually accepted by UIKit framework (which, by the way, is HEX!).

So… you need to fire Photoshop, or find a website that does that for you. Well, i just found a nice app called HexColors. It’s in the Mac AppStore, and it’s free (go get it!).

UITableViewCell without borders!

Fri, 06 Apr 2012 14:21:40 +0000

Suppose that you have an UITableView with a borderColor. Everything is cool and easy… as long as you don’t need to break the mold.

But if you ever need to add just ONE single cell without borders, you’ll notice that there is no way to do it. Well, it turns out that there is. But it’s not a straightforward one. You simply need to do this:

UIView* emptyBackView = [[UIView alloc] initWithFrame:CGRectZero];
[cell setBackgroundView:emptyBackView];

[emptyBackView release];
emptyBackView = nil;

Magic, ha?. If you add an empty backgroundView (with its background set to clearColor), the cell’s border will be gone.

OSX: Renaming Fonts (For Free!)

Thu, 29 Mar 2012 23:22:07 +0000

I just got a huge problem. I’m working on an iOS app, and it turns out that we need to maintain compatibility with iOS 4. So… the problem is that we use custom fonts. A lot of them. That shouldn’t be an issue. BUT… i got to notice that iOS 4 supports up to two different fonts per family.

Long short story, if you’ve got a font family with… 5 different fonts, iOS 4 will load just two of them. So how do we solve it?.

NSMutableSet: Filtering Duplicate Elements

Tue, 20 Mar 2012 02:16:28 +0000

Suppose that your app has X amount cached objects. And suppose that there is a slight chance that.. since the backend doesn´t actually know what it is exactly that you have cached (and what you don´t have cached), it might send duplicates.

So… what do we do?. Shall we write a for routine checking dupes?. No way. There is a far more performant way to achieve this, and it requires less lines of code.

Grand Central Dispatch: Perform Block After Delay

Tue, 20 Mar 2012 02:06:21 +0000

We have seen in a previous post the proper way to write a singleton, with the help of our good friend Grand Central Dispatch.

In this opportunity, i´d like to share a goodie i´ve learnt few days ago. I suppose many of you had problems with the following scenario. You have to perform a task, which is time consuming, and you need to place, onscreen, an Activity Indicator.

Although the Activity Indicator performs the animation on its own thread, you need to “spare some time” in the main thread for it to begin working. I mean… you can execute [indicator startAnimating] right away. But… if you don´t release the main thread, even for a short moment, surprise!. The spinner won´t work.

UITableView: Make room for a new cell, and insert it!

Fri, 16 Mar 2012 22:06:35 +0000

Suppose you wanna insert a new row at the bottom of a table. The first thing you need to do is to calculate the content offset. Suppose you already know the height of the new cell, and it’s stored into the variable ’newCellsHeight’. Then…

CGPoint contentOffset = CGPointZero;

contentOffset.y = _tableView.contentSize.height
 + newCellsHeight
 - _tableView.frame.size.height
 + _tableView.contentInset.bottom;</pre>
Once you've calculated the contentOffset (considering the current contentInsets)... you should make sure it's a non-negative value, to prevent quirks:

// Do we need to scroll down?
if(contentOffset.y &gt; 0.0f)
{
 [_tableView setContentOffset:contentOffset animated:YES];
}

The last step would be to actually insert the rows. Please, consider that a delay should be applied, so the insert rows animations won’t break the scroll animation!

Xcode: Number of lines

Fri, 16 Mar 2012 21:52:49 +0000

I’ve been unable to figure out how to do this, actually, within Xcode. But this can also be accomplished by means of this short script:

find . "(" -name "*.m" -or -name "*.mm" -or -name "*.cpp" ")" -print | xargs wc -l

Google Chrome Plugins

Thu, 15 Mar 2012 03:21:01 +0000

Google Chrome’s time has come. I love this browser because… it’s the fastest thing out there. It had a lot of glitches when it was first released. I remember Facebook wouldn’t work fine on it… and of course, i had to fix the HTML of many of the websites i maintain.

But i stil love it. It gets updated in background… and you hardly get to notice it!. As almost everything out there… it’s better when tweaked… right?. So i’d like to recommend three different plugins, available in the Chrome Web Store:

Xcode 4.3.1

Thu, 15 Mar 2012 02:50:34 +0000

If you haven’t done so… go grab the latest release of Xcode. But beware… as soon as you download it, it’ll overwrite your current 4.3 installation. It comes without sdk’s 5.0 and below. So… as usually… i recommend you do that after your looong working journey.

Otherwise you might find yourself stuck watching the download progress bar. No… that didn’t happen to me… i swear!.

Bad thing is that Apple didn’t fix the Refactor functionality, yet. It’s getting kinda difficult to rename class names. For some reason, i keep getting an annoying popup saying that it cannot be done. There are several posts in stackoverflow saying that Dropbox might cause that… but my projects are not inside a Dropbox folder, so that option can be discarded.

Preventing crashes: JSON Parsers & Null entries!

Fri, 09 Mar 2012 16:35:06 +0000

How many times you got to parse a backend response, and tested if a given value is != nil?. Well, as it turns out, many parsers (such as JSONKit) will parse ’null’ values into an instance of NSNull. That might cause a crash… unless you write eeeverywhere… ‘!= nil && != [NSNull null]’.

So… a good idea would be to implement an NSDictionary extention, to do that. Right?. The method would look like this:

Filtering arrays with NSPredicate!

Fri, 09 Mar 2012 12:24:42 +0000

Suppose you wanna filter a collection of objects. Normally, you’d write a while loop, implement a comparison, and add the matching objects to a collection.

Well, there is an easier way!!. For the sake of this example, say you wanna filter the objects that have the BOOL ‘isEnabled set to YES. So, you could do the following:

NSPredicate* predicate = [NSPredicate predicateWithFormat:@"isEnabled == YES"]; NSArray *filteredArray = [myArray filteredArrayUsingPredicate:predicate];

Yet another powerful example of NSPredicate would be… remember ‘SELECT* WHERE FIELD IN(1, 2)’ ?. Guess what!

Memory Management Tips!

Thu, 08 Mar 2012 23:26:27 +0000

It’s REALLY recommended that you set to nil any pointer that has a reference to a released object. But it’s tedious, right?. [pointer release]; pointer = nil;.

Why don’t we use a macro instead??

#define LAWipe(x)         [x release]; x = nil;

Simple. Nice. This should help you lower down the BAD_ACCESS crashes!.

iOS Singletons

Thu, 08 Mar 2012 23:08:53 +0000

Suppose that… for whatever reason, you need to target iOS 3.x. Yes. You need to build an app that should run on any possible device. Or say that… you simply don’t wanna use GCD.

What’s the alternative to write a singleton?

+ (id)sharedInstance
{
 if(_instance = nil)
 {
 @synchronized(self)
 {
 if(_instance == nil)
 {
 _instance = [[[self class] alloc] init];
 }
 }
 }
 return _instance;
}

This is a nice alternative to the GCD option. The first time the instance is created, you’ll suffer the lag caused by the @synchronized block. But after that. it’s just an if. No context switch. No whatsoever! REALLY performant!

iOS Assertions

Thu, 08 Mar 2012 23:03:28 +0000

So… you write a new piece of code. You run it. Test it. Ship it!. And in two weeks, you end up flooded by iTunes Connect Crash Reports.

What happened?. It turned out that an attribute parsed from a backend response ended up being a NSString instead of an NSNumber. And it was only after an untested-and-specific-workflow that your application actually used that field.

How do we prevent this?. ASSERTIONS!. A good friend of mine teached me that… great software blows everywhere before getting published. If your code works perfectly… you should be scared!.

Grand Central Dispatch Singletons

Thu, 08 Mar 2012 22:46:41 +0000

So… what’s the recommended way (thread safety + performance) to implement a singleton?

Well.. it looks pretty much like this!

+ (instancetype)sharedInstance
{
 static dispatch_once_t pred;
 static Foo* bar = nil;

 dispatch_once(&pred, ^{ bar = [[Foo alloc] init]; });
 return bar;
}