Since when does Xcode no longer require forward method declarations and why?

问题

I noticed that Xcode (or more precisely the Apple LLVM compiler?) does not longer require forward method declarations. In other words, the following code builds without warnings:

@implementation Foo

-(void) foo {
    [self bar];
}

-(void) bar {}

@end

This used to throw a warning in -foo saying that Foo might not respond to -bar, right? Is the compiler smarter now or is this something else? I’m using Xcode 4.3.1 plus Apple LLVM compiler 3.1.

回答1:

This has definitely changed, and it looks like such forward declarations are not required in Xcode 4.3 & later. Cf. Private Methods in Objective-C, in Xcode 4.3 I no longer need to declare them in my implementation file ?.

回答2:

In my XCode 4.2, the warning is still there, moreover, when ARC is enabled, it is an error, not just a warning.

来源：https://stackoverflow.com/questions/9884533/since-when-does-xcode-no-longer-require-forward-method-declarations-and-why