Hi all,

Consider the following :

```c
// Things.h
@interface Things : NSObject
@property (strong, nonatomic) NSSomething * listOfThings;
@end

// Things.m
@implementation Things
// Some methods
@end

// MutableThings.h
@interface MutableThings : Things
- (instancetype) thingsPassingTest;
@end

// MutableThings.m
@implementation MutableThings
- (instancetype)thingsPassingTest
{
    // Do some stuff in order to return a subset of Things
    return newThings;
}
@end

```

I would like to be able to call `thingsPassingTest` for a `Things` object, and not a `MutableThings`.

Is there a way to call a subclass method ?

Or maybe am I going in the wrong direction ?