Swift Swizzled

概述objc中出于安全性和一致性考虑，用+(void)load()来实现 swift中load()方法不起作用了，在swift中写load()方法编译器会提示错误， 可以用initialize() 或者是直接写在application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject:A

objc中出于安全性和一致性考虑，用+(voID)load()来实现
swift中load()方法不起作用了，在swift中写load()方法编译器会提示错误，
可以用initialize() 或者是直接写在application(application: UIApplication,dIDFinishLaunchingWithOptions launchOptions: [NSObject:AnyObject]?) -> Bool

下面是在initialize() 实现的例子，修改项目中所有UIVIEwController的背景色
新建一个项目SwiftAlbum，为了代码修改起来方便，新建了一个AppLoad.swift文件

import UIKitextension UIVIEwController {    public overrIDe class func initialize() {        // make sure this isn't a subclass        if self !== UIVIEwController.self {            return        }        struct dispatchToken {            static var token: dispatch_once_t = 0        }        dispatch_once(&dispatchToken.token) {            let originalSelector = #selector(UIVIEwController.vIEwDIDLoad)            let swizzledSelector = #selector(self.lw_vIEwDIDLoad)            let originalMethod = class_getInstanceMethod(self,originalSelector)            let swizzledMethod = class_getInstanceMethod(self,swizzledSelector)            let addMethod = class_addMethod(self,originalSelector,method_getImplementation(swizzledMethod),method_getTypeEnCoding(swizzledMethod))            if addMethod {                class_replaceMethod(self,swizzledSelector,method_getImplementation(originalMethod),method_getTypeEnCoding(originalMethod))            }else {                method_exchangeImplementations(originalMethod,swizzledMethod)            }        }    }    func lw_vIEwDIDLoad() {        print("vIEwDIDLoad: \(NsstringFromClass(self.classForCoder))")        let albumClassname = NsstringFromClass(self.classForCoder)        if albumClassname.containsstring("SwiftAlbum") {            self.vIEw.backgroundcolor = UIcolor.init(colorliteralRed: 244/255,green: 244/255,blue: 244/255,Alpha: 1)        }    }}class AppLoad: NSObject {}

通过print(“vIEwDIDLoad:(NsstringFromClass(self.classForCoder))”)打印可以看到，项目中新建的UIVIEwController，都有一个工程名前缀，比如SwiftAlbum.XXXVIEwController

参考地址：http://nshipster.com/swift-objc-runtime/

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