It will not be rejected, but you will need to install the target deployment system for iOS 5, and users running iOS 4 will not be able to download and install your application.
To use this method only for iOS 5 and allow the application to run on iOS 4 (with blue tabs), follow these steps:
if ([UITabBar instancesRespondToSelector:@selector(setSelectedImageTintColor:)]) { [tabBarController.tabBar setSelectedImageTintColor:[UIColor redColor]]; }
This code can be safely run on iOS4.
Alternatively, see my answer to this question, which explains how to fully customize the colors of the tab icons in a way that works on any version of iOS: image of the tab element and selectedImage
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