Swift & the Objective-C Runtime

最新推荐文章于 2025-08-13 11:06:35 发布

转载最新推荐文章于 2025-08-13 11:06:35 发布 · 49 阅读

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CC 4.0 BY-SA版权

原文链接：http://www.cnblogs.com/newBlash/p/4884003.html

文章标签：

#runtime #swift

关联对象(Associated Objects)

extension UIViewController {
    private struct AssociatedKeys {
        static var DescriptiveName = "nsh_DescriptiveName"
    }

    var descriptiveName: String? {
        get {
            return objc_getAssociatedObject(self, &AssociatedKeys.DescriptiveName) as? String
        }
        set {
            if let newValue = newValue {
                objc_setAssociatedObject(
                    self,
                    &AssociatedKeys.DescriptiveName,
                    newValue as NSString?,
                    UInt(OBJC_ASSOCIATION_RETAIN_NONATOMIC)
                )
            }
        }
    }
}

方法交叉(Method Swizzling)

extension UIViewController {
    public override class func initialize() {
        struct Static {
            static var token: dispatch_once_t = 0
        }

        // make sure this isn't a subclass        
        if self !== UIViewController.self {
            return
        }

        dispatch_once(&Static.token) {
            let originalSelector = Selector("viewWillAppear:")
            let swizzledSelector = Selector("nsh_viewWillAppear:")

            let originalMethod = class_getInstanceMethod(self, originalSelector)
            let swizzledMethod = class_getInstanceMethod(self, swizzledSelector)

            let didAddMethod = class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))

            if didAddMethod {
                class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
            } else {
                method_exchangeImplementations(originalMethod, swizzledMethod);
            }
        }
    }

    // MARK: - Method Swizzling

    func nsh_viewWillAppear(animated: Bool) {
        self.nsh_viewWillAppear(animated)
        if let name = self.descriptiveName {
            println("viewWillAppear: \(name)")
        } else {
            println("viewWillAppear: \(self)")
        }
    }
}