Grand Central Dispatch: Perform Block After Delay

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.

So… the common solution is to split that method into two parts, and execute ‘performSelector: withObject: afterDelay:’. That´s where GCD comes in.
We can do the exact same thing… but with blocks!!. That´s SO MUCH COOL…!

[cc lang=”objc”]
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW,
0.1f * NSEC_PER_SEC);

dispatch_after(popTime, dispatch_get_main_queue(), ^(void)
     // …  Your code

Note: The delay, in this example, is of about 0.1 seconds.

OSX iStats

Apple did a pretty good job with OSX. You buy a new mac… and you get almost everything you need, ‘for free’. Any mac comes with iPhoto preinstalled, Mail, Calendar, Safari and even Garage Band. Basically it covers everything an average user needs to do.

There are really really few weak spots to OSX. I dare to say that… one of the few things OSX lacks is a nice widget to check out things such as the download speed… cpu load and temperature and even uptime. Good news is that there is a nice company called iSlayer, that has a reaaaaally cool Dashboard widget named ‘iStat‘ , which does exactly that.

It’s free… so you definitely don’t have an excuse not to download it. It has two modes: horizontal and vertical. You can tweak which indicators you want (and which ones you don’t want). Plus.. there is an iOS version, too. Go check it out!

Google Chrome: pageRank Tool

If you haven’t ever heard about it.. pageRank is one of the core components of it’s awesome algorithm. Roughly speaking, the concept is… you’re popular if people speaks about you. Right?. And if you’re popular, whatever you say should have a better ranking in google’s results.

Well, the idea is… there are several ‘root’ webpages that have a high pageRank (which is a number ranged from 0 to 10), and there is a formula to calculate the pagerank of a page.. based on the pagerank of the backlinks. It’s a graph.. and the pageRank flows from those ‘root webpages’.

So… this chrome plugin will help you check, seamlessly, the PR of any website you’re currently viewing. Why would you need that?. Simply curiosity… or SEO purposes. Of course!

Automating file download…!

I really don’t know if we’ll have file sharing services in… say… 5 years from now. Since megaupload has been taken down, and it’s CEO imprisoned, several other file sharing services have begun shutting down their services.

But many of them are still alive and kicking. So… whenever you need to download a huge amount of different files, manually entering the captchas (plus opening the links, one my one) turns into a tedious task.

That’s where jDownloader comes in. It’s a java based, multi platform app, which helps you download files form multiple sources. It has lots of plugins, and gets updated periodically. So chances are… it supports whatever filehosting service you’re using.

It has automatic captcha recognition (at least for several hostings). And if the hosting you’re using doesn’t have ‘auto-captcha-recog’, you’ll simply get a popup with the image itself.

It’s REALLY useful!

Useful Firefox Plugins

Google Chrome is definitely my favorite web browser. It has OSX Lion fullscreen support… it’s fast and lightweight, and Google itself is in charge of pushing it forward. But sometimes it just falls short… you just can’t find a suitable plugin for whatever you need to do. That’s the only reason i have firefox installed in my mac. Even the latest version of FF, release 11, doesn’t support OSX fullscreen feature.

So… let’s stop pointing out weak spots of this browser… and let’s go to the point!. The following plugins make my life easier. Really… so… i suggest you check them out.

  1. Firebug
    Yes… it’s also available for Chrome. But this version has far more functionality than the google counterpart. It’s really useful when you’re developing websites…!
  2. Video DownloadHelper
    Suppose you wanna download FLV files from whatever site you’re visiting. This is your friend!… it allows you to capture videos from a huge list of different websites.

I hope you find this helpful!

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