Search code examples
cocoacocoa-bindingskey-value-coding

Collection Object operator for @firstObject Key-value coding KVC

I'm often required to retrieve the 1st object belonging to a Set. (Using that object as a representative of that set.)

I envision a Collection Object operator, akin to the

@unionOfObjects

BUT clearly 

@firstObject

Is it possible to create such a Collection operator!

Solution

  • Currently there's no way to define custom collection operators. However, due to some internal magic there is a funny solution:

        NSSet *testSet = [NSSet setWithArray:@[@"one", @(1)]];

    id object = [testSet valueForKey:@"@anyObject"];
    NSLog(@"anyObject (%@): %@", NSStringFromClass([object class]), object);

    UPD: Forgot to mention another handy trick: you can use @lastObject on NSArray!