How to override iOS pure swift copy constructor

Question

A very simple example of iOS Swift inheritance with the copy constructor. When I try to compile this, Xcode complains that I'm overriding a function that was defined with the parameter type Base and in child it's Child.

I agree with the compiler that the type is different but still he should let me do it somehow without using a different function name...

import Foundation
import SpriteKit

class Base : SKSpriteNode
{
    private var a : Int = 0

    init(other: Base)
    {
        self.a = other.a
        super.init(fileNamed: "test")
    }

    required init?(coder aDecoder: NSCoder)
    {
        fatalError("init(coder:) has not been implemented")
    }
}

class Child : Base
{
    private var b : Int = 0

    init(other: Child)
    {
        self.b = other.b
        super.init(other: other)
    }   

    required init?(coder aDecoder: NSCoder)
    {
        fatalError("init(coder:) has not been implemented")
    }
}

So is there a way of doing this in Xcode 6 and Swift please? Cheers, TK

Edit: Unfortunately I wrote my question so that it's easily misunderstood. So it's really only about the copy constructor and nothing else. Adjusted the code from a simple pseudo code to actual code that does not compile because of the mentioned problem.

I'm getting `'super' members cannot be referenced in a root class` from the `super.init()` in `Base`, but removing that line allows me to compile fine. — David Skrundz, Jul 29 '15 at 16:15
Thx but it was merely a pseudo code. I extended the base from SKSpriteNode to point more to the copy constructor problem. — James Takarashy, Jul 30 '15 at 05:10

score 3 · Answer 1 · edited May 23 '17 at 12:31

Being a base class, Base does not need to call a designated initialiser from a superclass, since it does not have one. Remove that and all should be well.

Also, I believe your call to super in the child-class initialiser should come after assignment of local iVars.

class Base
{
    private var a : Int = 0

    init(other: Base)
    {
        self.a = other.a
    }
}

class Child : Base
{
     private var b : Int = 0

     init(other: Child)
     {
         self.b = other.b
         super.init(other: other)
     }
}

Edit due to re-phrase of question:

Your 'Base' class must now call a designated initialiser from the super-class. In this case, init(texture: SKTexture!, color: UIColor!, size: CGSize).

In your 'Child' class, you could check to see if other is of type Child and if so cast appropriately.

override init(other: Base)
{
    if other is Child {
        self.b = (other as! Child).b
    }
    super.init(other: other)
}

Also see top answer in How to implement copy constructor in Swift subclass? for further help.

Thx but it was merely a pseudo code. I extended the base from SKSpriteNode to point more to the copy constructor problem. So please look at the updated question. — James Takarashy, Jul 30 '15 at 05:11
@ init(texture: SKTexture!, color: UIColor!, size: CGSize) -> I know and thank you, but this has nothing to do with the problem. @ In your 'Child' class, you could check to see if other is of type Child and if so cast appropriately -> this is not an acceptable solution for many reasons, thx anyway. — James Takarashy, Aug 03 '15 at 11:30

How to override iOS pure swift copy constructor

1 Answers1