Swift function swizzling / runtime

Before Swift, in Objective-C I would swizzle or hook methods in a class using <objc/runtime.h>.

If anyone has any info on the topic of modifying Swift's runtime and hooking functions like CydiaSubstrate and other libraries that helped in this area, please inform me.

I've succeed with method swizzling in Swift. This example shows how to hook description method on NSDictionary

My implementation:

extension NSDictionary {
     func myDescription() -> String!{
        println("Description hooked")
        return "Hooooked " + myDescription();
    }
}

Swizzling code:

func swizzleEmAll() {
        var dict:NSDictionary = ["SuperSecret": kSecValueRef]
        var method: Method = class_getInstanceMethod(object_getClass(dict), Selector.convertFromStringLiteral("description"))

        println(dict.description) // Check original description

        var swizzledMethod: Method = class_getInstanceMethod(object_getClass(dict), Selector.convertFromStringLiteral("myDescription"))
        method_exchangeImplementations(method, swizzledMethod)

        println(dict.description) //Check that swizzling works
    }

Edited: This code will work for any custom Swift class that inherits from NSObject (but will not work for classes that don't.) More examples - https://github.com/mbazaliy/MBSwizzler