What protocol needs to be additionally implemented to support working with different collection types?

To support working with different types of collections in iOS, it is often necessary to implement the Collection protocol (or its subprotocols, such as Sequence, BidirectionalCollection).

This protocol defines basic requirements for collections — the ability to iterate, access elements by index, etc. Thanks to this, you can write generic code that works with any collections (arrays, lists, dictionaries, etc.).

Example of using the Collection protocol:

func printElements<C: Collection>(_ collection: C) {
    for element in collection {
        print(element)
    }
}

let array = [1, 2, 3]
let set: Set = [4, 5, 6]

printElements(array) // works with array
printElements(set)   // works with set

Thus, implementing the Collection protocol allows unifying work with different collection types.