如何实现方法swizzling swift 3.0？

我如何在Swift 3.0中实现方法swizzling？

我已经阅读了nshipster的文章 ，但在这个代码的块

struct Static { static var token: dispatch_once_t = 0 } 

编译器给我一个错误

dispatch_once_t在Swift中不可用：改用lazily初始化的全局variables

Answer 1

首先dispatch_once_t在Swift 3.0中不可用。 你可以select两种select：

1. 全局variables

2. struct ， enum或class静态属性

有关更多详细信息，请参阅Swift 3中的dispatch_once

为了不同的目的，你必须使用不同的混合实现

• Swizzling CocoaTouch类，例如UIViewController;
• Swizzling自定义Swift类;

Swizzling CocoaTouch类

使用全局variables的示例swizzling viewWillAppear(_:)的UIViewController

 private let swizzling: (UIViewController.Type) -> () = { viewController in let originalSelector = #selector(viewController.viewWillAppear(_:)) let swizzledSelector = #selector(viewController.proj_viewWillAppear(animated:)) let originalMethod = class_getInstanceMethod(viewController, originalSelector) let swizzledMethod = class_getInstanceMethod(viewController, swizzledSelector) method_exchangeImplementations(originalMethod, swizzledMethod) } extension UIViewController { open override class func initialize() { // make sure this isn't a subclass guard self === UIViewController.self else { return } swizzling(self) } // MARK: - Method Swizzling func proj_viewWillAppear(animated: Bool) { self.proj_viewWillAppear(animated: animated) let viewControllerName = NSStringFromClass(type(of: self)) print("viewWillAppear: \(viewControllerName)") } } 

Swizzling自定义Swift类

要使用Swift类的Swizzling方法，你必须遵守两个要求（ 更多细节 ）：

• 包含要debugging的方法的类必须扩展NSObject
• 您要调整的方法必须具有dynamic属性

以及自定义Swift基类Person示例swizzling方法

 class Person: NSObject { var name = "Person" dynamic func foo(_ bar: Bool) { print("Person.foo") } } class Programmer: Person { override func foo(_ bar: Bool) { super.foo(bar) print("Programmer.foo") } } private let swizzling: (Person.Type) -> () = { person in let originalSelector = #selector(person.foo(_:)) let swizzledSelector = #selector(person.proj_foo(_:)) let originalMethod = class_getInstanceMethod(person, originalSelector) let swizzledMethod = class_getInstanceMethod(person, swizzledSelector) method_exchangeImplementations(originalMethod, swizzledMethod) } extension Person { open override class func initialize() { // make sure this isn't a subclass guard self === Person.self else { return } swizzling(self) } // MARK: - Method Swizzling func proj_foo(_ bar: Bool) { self.proj_foo(bar) let className = NSStringFromClass(type(of: self)) print("class: \(className)") } } 

Answer 2

@TikhonovAlexander：很好的答案

我修改了swizzler来select两个select器，并使其更通用。

Swift 3

 private let swizzling: (AnyClass, Selector, Selector) -> () = { forClass, originalSelector, swizzledSelector in let originalMethod = class_getInstanceMethod(forClass, originalSelector) let swizzledMethod = class_getInstanceMethod(forClass, swizzledSelector) method_exchangeImplementations(originalMethod, swizzledMethod) } // perform swizzling in initialize() extension UIView { open override class func initialize() { // make sure this isn't a subclass guard self === UIView.self else { return } let originalSelector = #selector(layoutSubviews) let swizzledSelector = #selector(swizzled_layoutSubviews) swizzling(self, originalSelector, swizzledSelector) } func swizzled_layoutSubviews() { swizzled_layoutSubviews() print("swizzled_layoutSubviews") } } 

斯威夫特4

 private let swizzling: (AnyClass, Selector, Selector) -> () = { forClass, originalSelector, swizzledSelector in let originalMethod = class_getInstanceMethod(forClass, originalSelector) let swizzledMethod = class_getInstanceMethod(forClass, swizzledSelector) method_exchangeImplementations(originalMethod, swizzledMethod) } extension UIView { static let classInit: Void = { let originalSelector = #selector(layoutSubviews) let swizzledSelector = #selector(swizzled_layoutSubviews) swizzling(UIView.self, originalSelector, swizzledSelector) }() func swizzled_layoutSubviews() { swizzled_layoutSubviews() print("swizzled_layoutSubviews") } } // perform swizzling in AppDelegate.init() @UIApplicationMain class AppDelegate: UIResponder, UIApplicationDelegate { override init() { super.init() UIView.classInit } } 

Answer 3

在操场上嬉戏

 class TestSwizzling : NSObject { dynamic func methodOne()->Int{ return 1 } } extension TestSwizzling { //In Objective-C you'd perform the swizzling in load(), //but this method is not permitted in Swift func initialize1() { let i: () -> () = { let originalSelector = #selector(TestSwizzling.methodOne) let swizzledSelector = #selector(TestSwizzling.methodTwo) let originalMethod = class_getInstanceMethod(TestSwizzling.self, originalSelector); let swizzledMethod = class_getInstanceMethod(TestSwizzling.self, swizzledSelector) method_exchangeImplementations(originalMethod, swizzledMethod) print("swizzled") } i() } func methodTwo()->Int{ // It will not be a recursive call anymore after the swizzling return 4 } } var c = TestSwizzling() c.initialize1() print(c.methodOne()) print(c.methodTwo()) 

输出：4 1