如何实现方法 swizzling swift 3.0？

Question

如何在 Swift 3.0 中实现方法调配？

我已经阅读了nshipster article 的相关信息，但在这段代码中

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：使用延迟初始化 改为全局变量

Answer 1

首先dispatch_once_t 在 Swift 3.0 中不可用。 您可以从两种选择中进行选择：

1. 全局变量

2. struct、enum 或 class 的静态属性

更多详情请看Whither dispatch_once in Swift 3

为了不同的目的，你必须使用不同的 swizzling 实现

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

混合 CocoaTouch 类

使用全局变量对UIViewController 的viewWillAppear(_:) 进行调配示例

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

要在您的 Swift 类中使用方法调配，您必须遵守两个要求 (for more details)：

• 包含要混合的方法的类必须扩展 NSObject
• 您要调配的方法必须具有dynamic 属性

以及自定义Swift基类Person的示例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

我修改了调酒器以采用两个选择器并使其更通用。

斯威夫特 4 / 斯威夫特 5

private let swizzling: (AnyClass, Selector, Selector) -> () = { forClass, originalSelector, swizzledSelector in
    guard
        let originalMethod = class_getInstanceMethod(forClass, originalSelector),
        let swizzledMethod = class_getInstanceMethod(forClass, swizzledSelector)
    else { return }
    method_exchangeImplementations(originalMethod, swizzledMethod)
}

extension UIView {
    
    static let classInit: Void = {            
        let originalSelector = #selector(layoutSubviews)
        let swizzledSelector = #selector(swizzled_layoutSubviews)
        swizzling(UIView.self, originalSelector, swizzledSelector)
    }()
    
    @objc func swizzled_layoutSubviews() {
        swizzled_layoutSubviews()
        print("swizzled_layoutSubviews")
    }
    
}

// perform swizzling in AppDelegate.init()

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    override init() {
        super.init()
        UIView.classInit
    }

}

斯威夫特 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")
    }
    
}

Answer 3

在 Playground 中嬉戏
Swift 5

import Foundation
class TestSwizzling : NSObject {
    @objc dynamic func methodOne()->Int{
        return 1
    }
}

extension TestSwizzling {
    @objc func methodTwo()->Int{
        // It will not be a recursive call anymore after the swizzling
        return 2
    }
    //In Objective-C you'd perform the swizzling in load(),
    //but this method is not permitted in Swift
    func swizzle(){
        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()
    }
}

var c = TestSwizzling()
print([c.methodOne(), c.methodTwo()])  // [1, 2]
c.swizzle()                            // swizzled!
print([c.methodOne(), c.methodTwo()])  // [2, 1]

Answer 4

Swiftswizzling

@objcMembers
class sA {
    dynamic
    class func sClassFooA() -> String {
        return "class fooA"
    }

    dynamic
    func sFooA() -> String {
        return "fooA"
    }
}

@objcMembers
class sB {
    dynamic
    class func sClassFooB() -> String {
        return "class fooB"
    }

    dynamic
    func sFooB() -> String {
        return "fooB"
    }
}

Swizzling.swift

import Foundation

@objcMembers
public class Swizzling: NSObject {

    public class func sExchangeClass(cls1: AnyClass, sel1: Selector, cls2: AnyClass, sel2: Selector) {

        let originalMethod = class_getClassMethod(cls1, sel1)
        let swizzledMethod = class_getClassMethod(cls2, sel2)

        method_exchangeImplementations(originalMethod!, swizzledMethod!)
    }

    public class func sExchangeInstance(cls1: AnyClass, sel1: Selector, cls2: AnyClass, sel2: Selector) {

        let originalMethod = class_getInstanceMethod(cls1, sel1)
        let swizzledMethod = class_getInstanceMethod(cls2, sel2)

        method_exchangeImplementations(originalMethod!, swizzledMethod!)
    }
}

通过 Swift 使用

func testSExchangeClass() {
    Swizzling.sExchangeClass(cls1: sA.self, sel1: #selector(sA.sClassFooA), cls2: sB.self, sel2: #selector(sB.sClassFooB))

    XCTAssertEqual("class fooB", sA.sClassFooA())
}

func testSExchangeInstance() {
    Swizzling.sExchangeInstance(cls1: sA.self, sel1: #selector(sA.sFooA), cls2: sB.self, sel2: #selector(sB.sFooB))

    XCTAssertEqual("fooB", sA().sFooA())
}

[Add Objective-C as an consumer]

通过 Objective-C 使用

- (void)testSExchangeClass {
    [Swizzling sExchangeClassWithCls1:[cA class] sel1:@selector(cClassFooA) cls2:[cB class] sel2:@selector(cClassFooB)];

    XCTAssertEqual(@"class fooB", [cA cClassFooA]);
}

- (void)testSExchangeInstance {
    [Swizzling sExchangeInstanceWithCls1:[cA class] sel1:@selector(cFooA) cls2:[cB class] sel2:@selector(cFooB)];

    XCTAssertEqual(@"fooB", [[[cA alloc] init] cFooA]);
}

[Objective-C swizzling]

Answer 5

斯威夫特 5.1

Swift 使用 Objective-C 运行时特性来进行方法混用。这里有两种方法。

注意：open override class func initialize() {} 不再允许使用。

1. 类继承NSObject，方法必须有dynamic属性

   class Father: NSObject {
      @objc dynamic func makeMoney() {
          print("make money")
      }
   }
   extension Father {
      static func swizzle() {
          let originSelector = #selector(Father.makeMoney)
          let swizzleSelector = #selector(Father.swizzle_makeMoney)
          let originMethod = class_getInstanceMethod(Father.self, originSelector)
          let swizzleMethod = class_getInstanceMethod(Father.self, swizzleSelector)
          method_exchangeImplementations(originMethod!, swizzleMethod!)
      }
      @objc func swizzle_makeMoney() {
          print("have a rest and make money")
      }
   }
   Father.swizzle()
   var tmp = Father()
   tmp.makeMoney() //  have a rest and make money
   tmp.swizzle_makeMoney() // make money
   

   1. 使用@_dynamicReplacement(for: )

      class Father {
          dynamic func makeMoney() {
              print("make money")
          }
      }
      extension Father {
          @_dynamicReplacement(for: makeMoney())
          func swizzle_makeMoney() {
              print("have a rest and make money")
          }
      }
      Father().makeMoney() // have a rest and make money
   

Answer 6

试试这个框架：https://github.com/623637646/SwiftHook

let object = MyObject()
let token = try? hookBefore(object: object, selector: #selector(MyObject.noArgsNoReturnFunc)) {
    // run your code
    print("hooked!")
}
object.noArgsNoReturnFunc()
token?.cancelHook() // cancel the hook

在 Swift 中挂钩方法非常容易。