How to add variable in existing class in swift?

I know that in swift we can use Extensions to add new methods to existing classes.

But what about if i want to add a variable?

extension UIViewController {

    var myVar = "xyz"
}

It gives like :

Extensions must not contain stored properties

Solution

We can't add the stored properties to extensions directly but we can have the computed variables.

extension UIViewController {
    var myVar: String {
        return "xyz"
    }
}

Extensions in Swift can:

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