How to make a mutating function in an extension return Int using Swift?

Question

Why doesn't this code work?

protocol ExampleProtocol {
    var simpleDescription: String { get }
    mutating func adjust()
}

extension Int: ExampleProtocol {

    var simpleDescription: String {
        return "The number \(self)"
    }

    mutating func adjust() {
        self += 42
    }
}

var x:Int = 7
let y:Int = x.adjust()

here is what I get on XCODE

is there a way to make adjust() return Int without changing its definition in the protocol?

Answer 1

Yes, you can give adjust a return value. Define it to return an Int in the protocol and class, then have it return itself in the mutating method:

protocol ExampleProtocol {
    var simpleDescription: String { get }
    mutating func adjust() -> Int
}
extension Int: ExampleProtocol {
    var simpleDescription: String {
    return "The number \(self)"
    }
    mutating func adjust() -> Int {
        self += 42
        return self
    }
}
var x:Int = 7
let y:Int = x.adjust() //49