Cocoa singleton and shared instances

Question

Why doesn't Apple have classes like pure singleton, for example, although the UIApplication class gives you access to the UIApplication singleton, for example:

UIApplication *sharedApplication = [UIApplication sharedApplication];

Nothing prevents you from explicitly creating an instance of UIApplication, for example:

UIApplication *newApplication = [[UIApplication alloc] init];

The result, however, is an exception. The exception clearly states that only one instance of the UIApplication class can be available at any time.

Then why not get a clean singleton by returning the same instance to the default initializer?

I ask this question in order to have clarity when creating a singleton in my project in order to keep track of which way is better.

Answer 1

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}

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