如何在Swift 3.0中实现方法swizzling？

我读过nshipster关于它的文章，但在这段代码的区块中

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：使用延迟初始化全局而非

首先，dispatch_once_t在Swift 3.0中不可用。您可以从两个选项中进行选择：

全局变量
struct、enum或class 的静态特性

有关更多详细信息，请参阅Swift 3 中的Whither dispatch_once

为了不同的目的，您必须使用不同的swizzling实现

滑动CocoaTouch类，例如UIViewController

Swizzling自定义Swift类

Swizzling CocoaTouch类

使用全局变量刷新UIViewController的viewWillAppear(_:)的示例

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Swift类中使用方法swizzling，您必须遵守两个要求(了解更多详细信息(：

包含要swizzled的方法的类必须扩展NSObject
要swizzle的方法必须具有dynamic属性

以及自定义Swift基类Person的swizzling方法示例

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)")
    }
}

@TikhonovAlexander：伟大的答案

我修改了swizzler以同时使用两个选择器，并使其更通用。

Swift 4/Swift 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
    }
}

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")
    }
    
}

在操场上滑动
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]

快速摆动

@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"
    }
}

Swizzing.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())
}

[添加Objective-C作为消费者]

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〕

Swift 5.1

Swift使用Objective-C运行时特性来实现方法swizzling。给你两条路。

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

类继承NSObject，方法必须具有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

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

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中挂接方法非常容易。

如何实现swizzling swift 3.0的方法

为了不同的目的，您必须使用不同的swizzling实现

Swizzling CocoaTouch类

Swizzling自定义Swift类

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