Compiling an app that works in iOS 6 and iOS 7

Question

I'm struggling to compile an iPad app for use on iOS 6 and iOS 7.

Here's the message I keep getting:

Property 'barTintColor' not found on object of type 'UITabBar *'; did you mean 'tintColor'?

The Base SDK for the target is set to Latest iOS (iOS 7.0), and the iOS Deployment Target is iOS 6.0. I did a Clean on the project.

Here is the code:

In the .h file:

@property (nonatomic, strong) IBOutlet UITabBar *tabbedBar;

In the .m file:

if ([tabbedBar respondsToSelector: @selector(barTintColor)]) {
     tabbedBar.barTintColor = [UIColor blackColor];
}

I'm compiling against the iOS 7 SDK, so it should know about barTintColor. Any idea what the problem could be?

Updated:

Okay, I'm making progress, but not quite understanding why.

See this Xcode screenshot. Note the two entries for my iPad 3 in the Active Scheme selection. What is the difference? If I choose the top option, I get the error. If I choose the bottom option, it works.

Can anyone explain why the same device appears twice in this list, and why it works when I choose one and not the other? FYI, the device has iOS 6 installed.

Answer 1

You have two SDKs installed in your Xcode: for iOS 6 and iOS 7. Now, when that happens, if you plug in your iOS 7 device, it shows as two devices (i.e. options) in the device selector: first row is for iPad 3 (iOS 6), second for iPad 3 (iOS 7).

The problem with your error is that when you select iPad 3 (iOS 6), Xcode still reads the device as iOS 7 (and that's what it has installed, anyway) so when building it passes the [tabbedBar respondsToSelector: @selector(barTintColor)] code (it responds to the selector, 'cause hey, it's iOS 7), but because you're building for iOS 6, at the same time it raises an error, 'cause hey, iOS 6 doesn't have that method! Fun.

Basically, you can't use the iOS 6 option when testing on the iOS 7 device. You either need a iOS 6 device, or you're stuck with the simulator for testing old versions.

EDIT: You can test what I'm saying in the following manner — instead of using respondsToSelector: use

if ([[[UIDevice currentDevice] systemVersion] floatValue] >= 7.0f) {
    // code
}

and then select the first device in the list (iPad 3 iOS 6). You'll see that you go through the if clause, but Xcode gives you an error that the selector isn't available on iOS 6.