ward.swift

//: Playground - noun: a place where people can play

import UIKit

func ward<T: AnyObject, A, Return>(_ object: T?, _ keyPath: KeyPath<T, (A) -> Return>, else defaultValue: Return) -> ((A) -> Return) {
    return { [weak object] a in
        guard let object = object else {
            return defaultValue
        }
        
        return object[keyPath: keyPath](a)
    }
}

func ward<T: AnyObject, A>(_ object: T?, _ keyPath: KeyPath<T, (A) -> Void>) -> ((A) -> Void) {
    return { [weak object] a in
        guard let object = object else {
            return
        }
        
        object[keyPath: keyPath](a)
    }
}

func ward<T: AnyObject, A, B>(_ object: T?, _ keyPath: KeyPath<T, (A, B) -> Void>) -> ((A, B) -> Void) {
    return { [weak object] a, b in
        guard let object = object else {
            return
        }
        
        object[keyPath: keyPath](a, b)
    }
}

func ward<T: AnyObject>(_ object: T?, _ keyPath: KeyPath<T, () -> Void>) -> (() -> Void) {
    return { [weak object] in
        guard let object = object else {
            return
        }
        
        object[keyPath: keyPath]()
    }
}

class MyClass {
    
    let anOutput: () -> Void = {
        print("here")
    }
    
    let boolOutput: (Bool) -> Bool = { boolVal in
        return !boolVal
    }
    
    let multiParam: (String, Int) -> Void = { string, int in
        print(string)
        print(int)
    }
}

extension KeyPath where Root == MyClass, Value == (() -> Void) {
    static var anOutPut: KeyPath<MyClass, () -> Void> { return \MyClass.anOutput }
}

extension KeyPath where Root == MyClass, Value == ((Bool) -> Bool) {
    static var boolOutput: KeyPath<MyClass, (Bool) -> Bool> { return \MyClass.boolOutput }
}

extension KeyPath where Root == MyClass, Value == ((String, Int) -> Void) {
    static var multiParam: KeyPath<MyClass, (String, Int) -> Void> { return \MyClass.multiParam }
}

var vc: MyClass? = MyClass()

var funk: () -> Void = ward(vc, .anOutPut)

vc = nil

funk()

vc = MyClass()

let boolFunk = ward(vc, .boolOutput, else: false)

print(boolFunk(true))

let wowza = ward(vc, .multiParam)

wowza("Hey", 2)