How can I check if a feature is available on a specific iOS version?

Question

In my AppDelegate I am using the appearance proxy to make custom UI:

//Setup custom appearances
    [[UINavigationBar appearance] setBackgroundImage:[UIImage imageNamed:@"header"] forBarMetrics:UIBarMetricsDefault];
    [[UINavigationBar appearance] setTintColor:[UIColor blackColor]];
    [[UIToolbar appearance] setBackgroundImage:[UIImage imageNamed:@"header"] forToolbarPosition:UIToolbarPositionAny barMetrics:UIBarMetricsDefault];

This will crash in iOS4. How can I check if this feature is available on the iOS version they are running, so I can avoid the crash?

possible duplicate of [Check iPhone iOS Version](http://stackoverflow.com/questions/3339722/check-iphone-ios-version) — jscs, Nov 05 '11 at 02:27

score 19 · Accepted Answer · answered Nov 04 '11 at 20:13

19

Don't check the OS, check if the capability exists.

if ([[UINavigationBar class] respondsToSelector:@selector(appearance)]) {}

answered Nov 04 '11 at 20:13

Joshua Weinberg

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Shocking. I don't see any harm in checking OS version. The mere presence of a symbol does not make its underlying implementation equal between OS releases. – bioffe Nov 04 '11 at 20:20
5

Apple does not recommend checking the version. You should look for features you are interested in, as @joshua stated. – logancautrell Nov 04 '11 at 20:23
1

While I agree fundamentally (except in rare cases), I believe that recommending a different method is not a complete answer. An exception case for me was a workaround for a frameworks bug in iOS 4 that caused issues in iOS 5, where the APIs were unchanged. A complete answer answers the question, then recommends the better method. – Jacob Jennings Nov 04 '11 at 21:47
Working around OS bugs is a whole different issue. – Joshua Weinberg Nov 04 '11 at 22:39
Actually ```- respondsToSelector``` is an instance method. For classes you should use ```class_respondsToSelector(Class c, SEL s);``` – Javier Soto May 15 '12 at 03:44
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classes are objects, calling an instance method on the class like I did is perfectly valid, and will give the results expected. – Joshua Weinberg May 15 '12 at 07:17
instead of `[[UINavigationBar class] respondsToSelector:@selector(appearance)]` you can just do `[UINavigationBar respondsToSelector:@selector(appearance)]` – user102008 Jun 12 '12 at 21:52

score 1 · Answer 2 · answered Nov 04 '11 at 20:17

1

Try this:

[UIDevice currentDevice].systemVersion

answered Nov 04 '11 at 20:17

borisdiakur

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Thanks for the down vote. The question was previously "How can I check if a user is on iOS4 or iOS5?" by the way. – borisdiakur Feb 12 '12 at 22:28
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People should validate the facts before down voting. – Rashmi Ranjan mallick May 04 '17 at 08:22

How can I check if a feature is available on a specific iOS version?

2 Answers2