NSPredicate针对NSArray中的嵌套值

Question

I have an NSArray of SKNodes, and am trying to use an NSPredicate to sort on the location.y values of the SKNodes using a predicate filter. I am trying the following, but at runtime I am getting the 'this class is not key value coding-compliant for the key y' So, I assume I have to do something else to filter on a subcompnent of the object? IS this possible?

NSSortDescriptor *descriptor = [NSSortDescriptor sortDescriptorWithKey:@"position.y"
                                                             ascending:YES];
NSArray *results = [myarrayofsknodes sortedArrayUsingDescriptors:[NSArray arrayWithObject:descriptor]];

Answer 1

The comment by LearnCocos2D is correct. However, you can sort other ways.

NSArray *original; // Populate this elsewhere
NSArray *results = [original sortedArrayUsingComparator:^(MyObject *obj1, MyObject *obj2) {
    if (obj1.position.y==obj2.position.y) {
        return NSOrderedSame;
    } else if (obj1.position.y < obj2.position.y) {
        return NSOrderedAscending;
    } else {
        return NSOrderedDescending;
    }
}];