Overriding a stored property in Swift

Question

I noticed that the compiler won\'t let me override a stored property with another stored value (which seems odd):

class Jedi {
    var lightSaberColor = \"Bl         


        

Answer 1

For me, your example does not work in Swift 3.0.1.

I entered in the playground this code:

class Jedi {
    let lightsaberColor = "Blue"
}

class Sith: Jedi {
    override var lightsaberColor : String {
        return "Red"
    }
}

Throws error at compile time in Xcode:

cannot override immutable 'let' property 'lightsaberColor' with the getter of a 'var'

No, you can not change the type of stored property. The Liskov Substitution Principle forces you to allow that a subclass is used in a place where the superclass is wanted.

But if you change it to var and therefore add the set in the computed property, you can override the stored property with a computed property of the same type.

class Jedi {
    var lightsaberColor = "Blue"
}


class Sith: Jedi {
    override var lightsaberColor : String {
        get {
            return "Red"
        }
        set {
            // nothing, because only red is allowed
        }
    }
}

This is possible because it can make sense to switch from stored property to computed property.

But override a stored var property with a stored var property does not make sense, because you can only change the value of the property.

You can, however, not override a stored property with a stored property at all.

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I would not say Sith are Jedi :-P. Therefore it is clear that this can not work.