How do I check if an NSSet contains an object of a kind of class?

Question

How would you implement the following instance method for NSSet:

- (BOOL)containsMemberOfClass:(Class)aClass

Here's why I want to know:

Core Data model:

How do I add a Facebook authorization to a user's authorizations NSSet, but only if one doesn't already exist. In other words, a user can have many authorizations (in case I choose to add a Twitter (e.g.) authorization in the future) but should only have one of each kind of authorization. So, if (![myUser.authorizations containsMemberOfClass:[Facebook class]]), then add a Facebook authorization instance to myUser.

Answer 1

Unfortunately, you have to loop through all of the authorizations and check:

@interface NSSet (ContainsAdditions)

- (BOOL)containsKindOfClass:(Class)class;
- (BOOL)containsMemberOfClass:(Class)class;

@end

@implementation NSSet (ContainsAdditions)

- (BOOL)containsKindOfClass:(Class)class {
    for (id element in self) {
        if ([element isKindOfClass:class])
            return YES;
    }
    return NO;
}

- (BOOL)containsMemberOfClass:(Class)class {
    for (id element in self) {
        if ([element isMemberOfClass:class])
            return YES;
    }
    return NO;
}

@end