Is there a way to use ObjectType in a category on NSArray?

Question

I've been trying to create a category on NSArray and looking at the interface of NSArray I assume that to add a method that returns an ObjectType, is:

// interface
- (nullable ObjectType)giveMeAnObject;

// implementation
- (nullable ObjectType)giveMeAnObject
{
    ObjectType object = nil;
    return object;
}

However that doesn't work and I get the error message Expected ')' in the return type.

Answer 1

It seems you can use lightweight generics in interfaces, but not implementations.

@interface NSArray<ObjectType> (MyAdditions)

- (nullable ObjectType)giveMeAnObject; // specify return type

@end


@implementation NSArray (MyAdditions)

- (id)giveMeAnObject // use id for the implementation
{
    return nil;
}

@end

You might want to file an enhancement request if you'd like to see them in @implementation blocks too.