Objective-C formatting string for boolean?

Question

What formatter is used for boolean values?

EDIT:

Example: NSLog(@\" ??\", BOOL_VAL);, what is ?? ?

Answer 1

I created a category of NSString with this

+ (instancetype)stringWithBool:(BOOL)boolValue {
return boolValue ? @"YES" : @"NO";
}

And use it like this:

[NSString stringWithBool:boolValue];