How to call IMP in Swift?

Question

Since Swift2 you can use good ole':

class_getMethodImplementation(cls: AnyClass!, _ name: Selector) -> IMP

It returns imp. In Objective-C you just call it like:

implementation(self, selector)

But how to call it in Swift?

Answer 1

Based on the article Instance Methods are Curried Functions in Swift it's pretty easy to achieve the desired result:

typealias MyCFunction = @convention(c) (AnyObject, Selector) -> Void
let curriedImplementation = unsafeBitCast(implementation, MyCFunction.self)
curriedImplementation(self, selector)

Answer 2

I was trying to get runtime calls working on an instance method with parameter(s). @Fabio's answer got me most of the way there. Here's a full example for future googlers:

import Foundation

class X {
  @objc func sayHiTo(name: String) {
    print("Hello \(name)!")
  }
}

let obj = X()
let sel = #selector(obj.sayHiTo)
let meth = class_getInstanceMethod(object_getClass(obj), sel)
let imp = method_getImplementation(meth)

typealias ClosureType = @convention(c) (AnyObject, Selector, String) -> Void
let sayHiTo : ClosureType = unsafeBitCast(imp, ClosureType.self)
sayHiTo(obj, sel, "Fabio")
// prints "Hello Fabio!"