Implementing copy() in Swift

Question

I want to be able to copy a custom class in Swift. So far, so good. In Objective-C I just had to implement the NSCopying protocol, which means implementing

Answer 1

Well, there is a really easy solution for this and you do not have to create root class.

protocol Copyable {
    init(instance: Self)
}

extension Copyable {
    func copy() -> Self {
        return Self.init(instance: self)
    }
}

Now, if you want to make your custom class be able to copy, you have to conform it to Copyable protocol and provide init(instance: Self) implementation.

class A: Copyable {
    var field = 0

    init() {
    }

    required init(instance: A) {
        self.field = instance.field
    }

}

Finally, you can use func copy() -> Self on any instance of A class to create a copy of it.

let a = A()
a.field = 1
let b = a.copy()