piątek, 19 czerwca 2015

Cocoa Touch Best Practices - WWDC 2015

Launch quickly

The first thing you learn is that you shouldn't do process extensive tasks on UI thread. People sometimes forget that if you do the same in the delegate callbacks you'll freeze UI.
  • Always return quickly from applicationDidFinishLaunching to launch the app as quickly as possible. Your app even might be killed if it takes too long!

Use Background Queues

Loading data from database or server on a main queue through dispatch_async is a basic thing. The problem is that if there are many operations on the main_queue it still may make the UI not responsive. The less time you spend wasting CPU cycles on the main thread, the more responsive your UI will be.
  • When dispatching use a background queue when possible

RAM Usage while suspended

When you go back to an app you instantly resume at the point where you've left it. It's a great thing in mobile devices, that lets us save our time and make the apps more responsive.

The sad truth is that your app might get killed from the suspension state. We want to make sure it lives as long as possible, right ? iOS kills the apps that use the most RAM first!

Don't bet that app!

  • When you get the applicationDidEnterBackground callback make sure you release as much data as possible. Use a background task if you need more time to clean after yourself.

Keep Your Code Unrelated To Time

Sometimes you want to do something after a certain animation finishes. You can predict how long will that animation last and just use a NSTimer and launch a block of code to happen after that time. What if in future iOS updates the time of the animation changes ? Try to keep your code relative to events and callbcks, not time. For example by using UIViewControllerTransitionCoordinator.