class TriangleAndSquare {
var triangle: EquilateralTriangle {
willSet {
square.sideLength = newValue.sideLength
}
}
var square: Square {
willSet {
triangle.sideLength = newValue.sideLength
}
}
init(size: Double, name: String) {
square = Square(sideLength: size, name: name)
triangle = EquilateralTriangle(sideLength: size, name: name)
}
}
var triangleAndSquare = TriangleAndSquare(size: 10, name: "another test shape")
print(triangleAndSquare.square.sideLength)
print(triangleAndSquare.triangle.sideLength)
triangleAndSquare.square = Square(sideLength: 50, name: "larger square")
print(triangleAndSquare.triangle.sideLength)
快速的协议就像Java中的接口？谁能解释我上面示例中的willSet和didSet到底做什么？
willSet属性值即将更改时，将调用in的代码。didSet，仅在更改属性值时被调用。如果可以帮助您，您可以认为协议就像接口一样，但是您可能想观看WWDC视频“面向协议的编程”，以了解协议在实践中是如何使用的。
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