Why do the allKeys and allValues ​​NSDictionary methods return an NSArray and not an NSSet?

Question

Naturally, the keys to are NSDictionarynot ordered, as well as its meanings.

So why methods allKeysand allValues NSDictionaryreturn NSArrayinstead NSSet?

Answer 1

A value can be repeated more than once in a dictionary, but not in a set. Therefore, returning an array returns all values, and returning a set returns only unique values.

The keys, of course, must be unique, so I would suggest that the choice of the array, and not the set, be simple consistency.