看了几天的Runtime ，教程还有简书的也大多都是OC的，结果要转成SWIFT的时候落进了一堆的大坑，还是专心看Swift就好吧 ...

WildDylan写的Runtime写的很清晰、很易入门：http://www.jianshu.com/p/9c36a5b7820a
在大神的基础上，练练手，存在extension UIViewController了，
也当把代码存在简书上，以后方便调用！

//
//  ViewController.swift
//  SwizzlingTestSwift
//
//  Created by Linus on 16/3/25.
//  Copyright © 2016年 Linus. All rights reserved.
//

import UIKit

class TestSwiftClass {
    
    @objc  var sex:Bool = true
    @objc var age:Int = 22
    @objc  var name:String = "Dylin"
    @objc   var cars:AnyObject! = nil
    
}

class ViewController: UIViewController {
 
   /*
    *
     http://www.163.com/中文 为 nil
     http://www.163.com/ 有值

    *
    */
    
   
    var sex:Bool = true
    var age:Int = 22
    var name:String = "Dylin"
    var cars:AnyObject! = nil

    
    override func viewDidLoad() {
        super.viewDidLoad()
          
      // 调用extension UIViewController里的函数，已黑魔法交换
        debugPrint("==",returnInt(1))
       
     
        
   }
  
    // 没有在 func 前加 dynamic 是交换不了的
    func returnTuple (_ name:String) -> (Bool,Int,String) {
        
        return (true,22,"Dylin")
    }
    
 
    
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

//
//  extension.swift

//
//  Created by apiapia on 3/16/17.
//  Copyright © 2017 Linus. All rights reserved.
//

import Foundation
import UIKit


extension UIViewController{
    
    // 初始化的时候就调用RunTime 黑魔法 
    
    open override static func initialize() {
        
        super.initialize()
        
        // 确保不是子类
        if self !== UIViewController.self {
            return
        }
        
        //黑魔法的使用
        mySwizzle(cls: self, origSEL: #selector(UIViewController.viewWillAppear),
                  newSEL: #selector(UIViewController.customViewWillAppear))
        mySwizzle(cls: self, origSEL: #selector(UIViewController.viewWillDisappear),
                  newSEL: #selector(UIViewController.customViewWillDisappear))
        mySwizzle(cls: self, origSEL: #selector(UIViewController.viewDidAppear),
                  newSEL: #selector(UIViewController.customViewDidAppear))
        
        
        mySwizzle(cls: self,
                                   origSEL: #selector(UIViewController.returnInt(_ :)),
                                   newSEL: #selector(UIViewController.new_returnInt(_ :)))

         
 }
 

    dynamic func returnInt (_ value:Int) -> Int {
        print("before")
        return 5
    }
    
    dynamic func new_returnInt (_ value:Int) -> Int {
        print ("new")
        return 10
    }
    
    func customViewWillAppear(animated: Bool) {
        self.customViewWillAppear(animated: animated)
        
    }
    
    func customViewWillDisappear(animated: Bool){
        self.customViewWillDisappear(animated: animated)
    }
    
    
    func customViewDidAppear(animated: Bool) {
        self.customViewDidAppear(animated: animated)
        print ("cusomViewDidAppear")
    }
    
    
    //交换方法函数
    class func mySwizzle(cls:AnyClass,origSEL:Selector,newSEL:Selector){
        //原有方法
        let originalMethod:Method = class_getInstanceMethod(cls, origSEL)
        //新方法（替换原有方法的新方法）
        let swizzleMethod:Method = class_getInstanceMethod(cls, newSEL)
        
        //先尝试給源SEL添加IMP，这里是为了避免源SEL没有实现IMP的情况
        let didAddMethod =  class_addMethod(cls, origSEL,
                                            method_getImplementation(swizzleMethod),
                                            method_getTypeEncoding(swizzleMethod))
        
        if didAddMethod {
            //添加成功：说明源SEL没有实现IMP，将源SEL的IMP替换到交换SEL的IMP
            class_replaceMethod(cls, newSEL,
                                method_getImplementation(originalMethod),
                                method_getTypeEncoding(originalMethod))
            
        }else {
            //添加失败：说明源SEL已经有IMP，直接将两个SEL的IMP交换即可
            method_exchangeImplementations(originalMethod, swizzleMethod)
        }

    }
    
    
}