Question

Hi does Apples iOS is having backward compatability? I’m having a doubt like in iOS 6 apple is introducing many new features like say for an example we have UICollectionView (for Grid) if i use this class & control of iOS6 then is there any flags or settings change or any extra code snippet available for developers so as to support iOS<6 also.

Answer 1

You can check UICollectionView's class availability with NSClassFromString function.

A simple example of Twitter :

Class TWTweetComposeViewControllerClass = NSClassFromString(@"TWTweetComposeViewController"); 

if (TWTweetComposeViewControllerClass != nil) 
{
     // this class only available in iOS 5
     // so new code
}
else
{
     // Means older version
}