Keypath for first element in embedded NSArray

Question

This example is contrived, but it shows my point.

So, if I have an object graph like the following:

{
sex = male;
uid = 637650940;
work = ({
    empl         


        

Answer 1

@PauldeLange - Your answer and links were helpful.
The following simpler version works too (at least as of Xcode 6)

id name = [work valueForKeyPath: @"employer.name.@firstObject”];

In the above 'firstObject' refers to the predefined method on NSArray. If the second object is needed, you can define the following:

@implementation NSArray (CustomKVOOperators)

- (id) secondObject {
    return [self count] >=2 ? self[1] : nil;
}
@end

And use:

 id name = [work valueForKeyPath: @"employer.name.@secondObject”];

Answer 2

Well to answer my own question, one way to do it is this:

1) Define the following category

@implementation NSArray (CustomKVOOperators)

- (id) _firstForKeyPath: (NSString*) keyPath {
    NSArray* array = [self valueForKeyPath: keyPath];
    if( [array respondsToSelector: @selector(objectAtIndex:)] &&
        [array respondsToSelector: @selector(count)]) {
        if( [array count] )
            return [array objectAtIndex: 0];
        else
            return nil;
    }
    else {
        return nil;
    }
}

@end

2) Use this KeyPath syntax

NSArray* work = [outerArrayObject objectForKey: @"work"];
id name = [work valueForKeyPath: @"@first.employer.name"];

Thanks to this clever person.