Objective-C Runtime的Associated Objects在swift中的使用

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用swift书写associated objects与一个给UIView添加角标的例子

最佳实践

matt大神在这里给出了一个最佳实践：

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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)
                )
            }
        }
    }
}

一个利用runtime添加角标的例子

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//用于显示小角标
extension UIView {
    
    //设置一个用于存放Objc-Runtime key 的结构体
    //参考资料http://nshipster.com/swift-objc-runtime/
    private struct AssociatedKeys {
        static var NumLabelKey = "Cooper_NumLaebel"
    }
    
    func showCornerStatus(badgeNumber:Int,rateX:CGFloat,rateY:CGFloat){
        self.removeCornerStatus()
        if badgeNumber == 0 {
            return
        }
        
        var labelWidth: CGFloat = 20
        var numLabel = UILabel(frame: CGRectMake(0, 0, labelWidth, labelWidth))
        var settingCenter = CGPointZero
        
        settingCenter.x = self.frame.width * rateX
        settingCenter.y = self.frame.width * rateY
        
        numLabel.center = settingCenter
        numLabel.layer.cornerRadius = labelWidth/2
        numLabel.clipsToBounds = true
        numLabel.backgroundColor = UIColor.redColor()
        numLabel.textColor = UIColor.whiteColor()
        numLabel.textAlignment = NSTextAlignment.Center
        numLabel.font = UIFont(name: "FZLanTingHeiS-R-GB", size: 10) ?? UIFont.systemFontOfSize(10)
        numLabel.text =  badgeNumber > 99 ? "..." : "\(badgeNumber)"
        
        //设置关联变量
        objc_setAssociatedObject(self,&AssociatedKeys.NumLabelKey, numLabel, UInt(OBJC_ASSOCIATION_RETAIN_NONATOMIC))
        
        self.addSubview(numLabel)
        
    }
    
    func removeCornerStatus(){
        var numLabel = objc_getAssociatedObject(self, &AssociatedKeys.NumLabelKey) as? UIView
        numLabel?.removeFromSuperview()
    }
}

用法：

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var btn = UIButton()
btn.showCornerStatus(8, rateX: 0.7, rateY: 0.12)

效果：
效果

参考资料

swift-objc-runtime