Does Objective-C have an equivalent to java annotations?

Question

Does Objective-C have an equivalent to java annotations?

What\'s I\'m trying to do is create a property and be able to somehow access some metadata about it.

Answer 1

Objective C does not support generics like in Java but ofcourse the language is very flexible that you can accomplish almost anything with simple tricks and knowledge. To implement a generic like feature you could create a category on NSArray class and create your own method to initialize the array and then check to see if the object is really the type of the object you want.

I would write a simple category on NSArray to have such functionality. Say suppose, I want my array to hold objects of class MyClass only then my category would look like,

@interface NSArray(MyCategory)

@end

@implementation NSArray(MyCategory)

-(NSArray*)arrayWithMyClasses:(NSArray*)classes{
    if([classes count] > 0){
        NSMutableArray *array = [[NSMutableArray alloc] init];
        for(id anObj in classes){
            NSAssert([anObj isKindOfClass:[MyClass class]], @"My array supports only objetcts of type MyClass");
            [array addObject:anObj];
        }
        return array;
    }
    return nil;
}
@end 

Of course, there is some limitations to it. Since you have created your own category, you should use your own method to initialize and create your own array.