How to implement subclasses of PFObject subclasses?

Question

I have a subclass A of a Parse PFObject defined as (details left out):

@interface A : PFObject <PFSubclassing>
@end
@implementation A
+ (void)load {
    [self registerSubclass];
}
+ (NSString *)parseClassName {
    return NSStringFromClass([self class]);
}
@end

I need a subclass B of A, defined as

@interface B : A <PFSubclassing>
@end
@implementation B
+ (void)load {
    [self registerSubclass];
}
+ (NSString *)parseClassName {
    return NSStringFromClass([self class]);
}
@end

A and B are registered in the AppDelegate by

[A registerSubclass];
[B registerSubclass];

I am not sure if this is the correct way to define subclasses of subclasses of PFObject:

https://www.parse.com/questions/what-does-this-error-mean-subclasses-of-subclasses-may-not-have-separate-parseclassname-definitions suggests that one should not define + (NSString *)parseClassName in subclass A, only in subclass B.
But if I do so, I get an error +[A parseClassName]: unrecognized selector sent to class when A’s registerSubclass method is called.
When I also leave out the + (void)load method of subclass A, and the call to [A registerSubclass] in the AppDelegate, the app seems to work.

So my question is:

Is it correct, to use only for the subclass at the lowest level <PFSubclassing>, + (NSString *)parseClassName, + (void)load, and register it in the AppDelegate, or which is the right way to do it?

Answer 1

To answer my own question; maybe this helps others (I have now used the following setup for 2 weeks, and everything seems to work fine):

If one has subclasses of PFObject subclasses, only for the lowest subclass in the hierarchy one has to do the following:

• Register it in the AppDelegate
• Adopt PFSubclassing and implement +(void)load and +(NSString *)parseClassName