Why NSMutableArray inherits from NSArray

Question

Why NSMutableArray inherits from NSArray

Answer 1

NSArray is actually a class cluster, refer to the official documentation https://developer.apple.com/l...

NSMutableArray is said to inherit it, but in fact many implementation methods are different. The above document uses NSNumber as an example at the beginning to show that NSNumber can actually be an int or a float. The principle is similar.

Answer 2

This is what people write in the document