StackOverflow2013

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copied!<p>You should always prefer detecting available methods/feature rather then iOS versions and then assuming a method is available.</p> <p>See <a href="http://developer.apple.com/library/mac/#documentation/developertools/conceptual/cross_development/Using/using.html" rel="noreferrer">Apple documentation</a>.</p> <p>For example, in iOS 5 to display a modal view controller we would do something like this:</p> <pre><code>[self presentModalViewController:viewController animated:YES]; </code></pre> <p>In iOS 6, the <code>presentModalViewController:animated:</code> method of <code>UIViewController</code> is Deprecated, you should use <code>presentViewController:animated:completion:</code> in iOS 6, but how do you know when to use what?</p> <p>You could detect iOS version and have an if statement dictate if you use the former or latter but, this is fragile, you'll make a mistake, maybe a newer OS in the future will have a new way to do this.</p> <p>The correct way to handle this is:</p> <pre><code>if([self respondsToSelector:@selector(presentViewController:animated:completion:)]) [self presentViewController:viewController animated:YES completion:^{/* done */}]; else [self presentModalViewController:viewController animated:YES]; </code></pre> <p>You could even argue that you should be more strict and do something like:</p> <pre><code>if([self respondsToSelector:@selector(presentViewController:animated:completion:)]) [self presentViewController:viewController animated:YES completion:^{/* done */}]; else if([self respondsToSelector:@selector(presentViewController:animated:)]) [self presentModalViewController:viewController animated:YES]; else NSLog(@"Oooops, what system is this !!! - should never see this !"); </code></pre> <p>I'm unsure about your <code>UIActionSheet</code> example, as far as I'm aware this is the same on iOS 5 and 6. Maybe you are thinking of <code>UIActivityViewController</code> for sharing and you might like to fallback to a <code>UIActionSheet</code> if you're on iOS 5, so you might to check a class is available, see <a href="http://www.lukessandbox.com/2012/checking-for-objective-c-class-availability.html" rel="noreferrer">here</a> how to do so.</p>

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