Comment mettre en œuvre la méthode swizzling swift 3.0?

Question

Comment puis-je implémenter la méthode swizzling dans Swift 3.0 ?

J'ai lu l' article de nshipster à ce sujet, mais dans le bloc de ce code

 struct Static {
    static var token: dispatch_once_t = 0
}
 

le compilateur me donne une erreur

dispatch_once_t n'est pas disponible dans Swift: utilisez plutôt des globaux initialisés paresseux

Answer 1

Tout d'abord dispatch_once_t n'est pas disponible dans Swift 3.0. Vous pouvez choisir entre deux alternatives:

1. Variable globale

2. Propriété statique d' struct, enum ou class

Pour plus de détails, voir que Où dispatch_once dans Swift 3

À des fins différentes, vous devez utiliser différents de mise en œuvre de swizzling

• Swizzling CocoaTouch classe, par exemple UIViewController;
• Swizzling personnalisé Swift classe;

Swizzling CocoaTouch classe

exemple swizzling viewWillAppear(_:) de UIViewController en utilisant la variable globale

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 personnalisé Swift classe

Pour utiliser la méthode swizzling rapide des classes il y a deux exigences que vous devez respecter (pour plus de détails):

• La classe contenant des méthodes à swizzled doit s'étendre NSObject
• Les méthodes que vous voulez swizzle doit avoir l' dynamic d'attribut

Et l'exemple swizzling méthode de la coutume Swift de la classe de base Person

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: excellente réponse

J'ai modifié le swizzler pour prendre les deux sélecteurs et le rendre plus générique.

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")
    }

}
 

Swift 4

 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
    }

}
 

Answer 3

balancer dans la cour de récréation
Swift 4.2

 import Foundation
class TestSwizzling : NSObject {
    @objc 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 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()
    }

    @objc func methodTwo()->Int{
        // It will not be a recursive call anymore after the swizzling
        return 4
    }
}

var c = TestSwizzling()
print([c.methodOne(),c.methodTwo()])
c.swizzle()
print([c.methodOne(),c.methodTwo()])
 

sortie:
[1, 4]
grillé
[4, 1]