Swift computed properties in Swift with instance variable?

Question

I'm trying to create a computed property in Swift and I need an instance variable to save the state of the property.

This happens specially when I'm trying to override a property in my superclass:

class Jedi {
    var lightSaberColor = "Blue"
}


class Sith: Jedi {
    var _color = "Red"
    override var lightSaberColor : String{
        get{
            return _color
        }
        set{
            _color = newValue
        }
    }

}

I'm overriding the stored property lightSaberColor in Jedi with a computed property because that's the only way the compiler will let me. It also forces me to create a getter and setter (which makes sense). And that's when I run into trouble.

So far, the only way I've found is to define this extra and ugly var _color. Is thee a more elegant solution?

I tried defining _color inside the property block, but it won't compile.

There's gotta be a better way!

Why do you need to override the property? There must be a reason behind that, and I think that can help in order to provide you a proper answer — Antonio, Nov 01 '14 at 19:30
It's just an example. The real question is how to handle iVars in computed properties — cfischer, Nov 01 '14 at 21:35

score 5 · Accepted Answer · answered Nov 01 '14 at 22:24

5

The way you have it is the only way it can work right now - the only change I would make is to declare _color as private.

Depending on your needs, it may be enough to have a stored property with willGet and/or didSet handlers.

answered Nov 01 '14 at 22:24

Nate Cook

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score 3 · Answer 2 · answered Nov 02 '14 at 03:30

3

Why not just set it in initializer?

class Jedi {
    var lightSaberColor = "Blue"
}

class Sith: Jedi {
    override init () {
        super.init()
        self.lightSaberColor = "Red"
    }
}

answered Nov 02 '14 at 03:30

Shuo

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Swift computed properties in Swift with instance variable?

2 Answers2