Is it possible in Swift to add variables to an object at runtime?

Question

Specifically, I would like to add a variable of type enum to an instance of UIView, without subclassing or create an extension.

Thanks.

Answer 1

Here is a simple but complete example derived from jckarter's answer.

It shows how to add a new property to an existing class. It does it by defining a computed property in an extension block. The computed property is stored as an associated object:

import ObjectiveC

// Declare a global var to produce a unique address as the assoc object handle
var AssociatedObjectHandle: UInt8 = 0

extension MyClass {
    var stringProperty:String {
        get {
            return objc_getAssociatedObject(self, &AssociatedObjectHandle) as String
        }
        set {
            objc_setAssociatedObject(self, &AssociatedObjectHandle, newValue, objc_AssociationPolicy(OBJC_ASSOCIATION_RETAIN_NONATOMIC))
        }
    }
}