Swift Swizzled

最新推荐文章于 2024-08-28 07:58:19 发布

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最新推荐文章于 2024-08-28 07:58:19 发布

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分类专栏： iOS 文章标签： swift swizzled

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本文介绍如何在Swift中利用initialize方法实现对所有UIViewController背景色的统一设置，通过运行时方法交换技巧达到目的，适用于希望保持界面一致性的iOS应用。

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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 UIKit

extension 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 {


}