Can I turn the error message "No visible @interface for 'FooClass' declares the selector 'bar'" back into a warning?

Question

- (void)doIt
{
    [_foo bar];
    // produces compile time error: "No visible @interface for 'FooClass'
    // declares the selector 'bar'"
}

In the earlier days of Objective-C, when I called a method that the compiler doesn't know about, I would just get a warning. Then, something like a year ago, the compiler changed and such things are now an error. Does anybody know when this happened (__weak ?)

What I did to solve the problem

There are a few methods that I know which can solve the problem, somehow. However, I hope there is an easier way.

A) declare an interface

@interface FooClass (MichaelHacksIt)
- (void) bar;
@end

// ...

- (void) doIt
{
    [_foo bar];
}

B) use -performSelector:

- (void)doIt
{
    [_foo performSelector:@selector(bar)];
}

C)

Because solution B sometimes produces an 'Undeclared selector' warning, and because we don't want Apple to know which methods we are calling, at all times, there is a third solution:

- (void)doIt
{
    SEL bar_sel = NSSelectorFromString(@"bar");
    [_foo performSelector:bar_sel];
}

D)

If the arguments to the method call are not just objects, we need to use NSInvocation instead. That's really ugly.

What I would like to do

Is there maybe some compiler switch that disables the error? Under the hood, a message send is always just a call to objc_msgSend(), and linking to the method implementation is done at runtime. So, disabling the error should in principle be possible. What I would like to do is something similar to:

- (void)doIt
{
    #pragma clang diagnostic push
    #pragma clang error disable objc_method_unknown_error
    [_foo bar];
    #pragma clang diagnostic pop
}

Is there such a compile time switch? Is there maybe a compiler flag that can be passed at the command line that produces this behaviour?

Why I am asking

These questions arise when you try to use undocumented methods. For example to change the status bar text color in iOS. Or to override some undocumented method in a subclass when you have the source, but you don't want to modify it for some reason.

Does my solution A have any effect at runtime? Is it possible somehow to see in the binary that I declared a private category (MichaelHacksIt) or does it just silence the compiler? (Note that there is no @implementation for this category.)

My main question is: Is it possible to disable the "No visible @interface for 'SomeClass' declares the selector 'fooBar'"?

Answer 1

The error message has been introduced together with Automatic Reference Counting.

More information about this particular error message and why it is now a fatal error in ARC can be found here.

(this is just a summary of the comments below the original question)