Swift return type clarification

Question

I see a Swift function written as follows:

func calculation(imageRef: CGImage) -> (red: [UInt], green: [UInt], blue: [UInt]) {

 ...
 ...
}

Answer 1

It's a tuple that this function is returning.

A tuple can hold various types in one object, but unlike an array, you cannot append or remove objects to/from it.

From Apple Developer Swift Guides:

Tuples group multiple values into a single compound value. The values within a tuple can be of any type and don’t have to be of the same type as each other.

Tuples don't exist in Objective-C. You can find more information about that here.