swift - 如何在 Swift 中覆盖 setter

Question

父类(super class):

class MySuperView : UIView{
    var aProperty ;
}

子类继承父类:

class Subclass : MySuperClass{
    // I want to override the aProperty's setter/getter method
}

我想覆盖父类(super class)属性的 setter/getter 方法，

如何在 Swift 中覆盖这个方法？请帮助我，谢谢。

Answer 1

你想用你的自定义二传手做什么？如果你想让类在设置值之前/之后做一些事情，你可以使用willSet/didSet:

class TheSuperClass { 
   var aVar = 0 
} 

class SubClass: TheSuperClass { 
     override var aVar: Int { 
         willSet { 
            print("WillSet aVar to \(newValue) from \(aVar)") 
        } 
        didSet { 
            print("didSet aVar to \(aVar) from \(oldValue)") 
        } 
    } 
} 


let aSub = SubClass()
aSub.aVar = 5

Console Output:

WillSet aVar to 5 from 0

didSet aVar to 5 from 0

但是，如果您想完全改变 setter 与父类(super class)交互的方式:

class SecondSubClass: TheSuperClass { 
     override var aVar: Int { 
        get {
            return super.aVar
        }
        set { 
            print("Would have set aVar to \(newValue) from \(aVar)") 
        } 
    } 
} 

let secondSub = SecondSubClass()
print(secondSub.aVar)
secondSub.aVar = 5
print(secondSub.aVar)

Console output:

0

Would have set aVar to 5 from 0

0