Swizzling

My notes on swizzling in swift.

Basic swizzling:

Swizzling is all about replacing the static “variable method” with another static variable method.
Bare in mind that all instances of that class also gets this new method variable
Basically instance api stays the same. And you only set a new internal static var that the internal api calls

import Cocoa

// Only needed until we have class variables
var __SwizzleSayHello = { (who: String) -> String in
    return "Hello, \(who)"
}

class Swizzle {
    // Only needed until we have class variables
    class var _sayHello : (String) -> String { get { return __SwizzleSayHello } set (swizzle) {__SwizzleSayHello = swizzle} }

    func sayHello(who: String) -> String{
        return Swizzle._sayHello(who)
    }
}

let immutableInstance = Swizzle()
var mutableInstance = Swizzle()

//Both print "Hello, World"
print(immutableInstance.sayHello("World"))
print(mutableInstance.sayHello("World"))

Swizzle._sayHello = { (who: String) -> String in
    return "Howdy, \(who)"
}

//Both print "Howdy, World"
print(immutableInstance.sayHello("World"))
print(mutableInstance.sayHello("World"))