協議willSet和didSet

Question

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)

快速的協議就像Java中的接口？ 誰能解釋我上面示例中的willSet和didSet到底做什么？

Answer 1

1.物業觀察員

• 當屬性值即將更改時，將調用willSet代碼。
• 另一方面，當屬性值剛剛更改時， didSet會被調用。

2.協議

如果可以幫助您，您可以認為協議就像接口一樣，但是您可能希望觀看WWDC視頻“面向協議的編程”，以了解協議在實踐中是如何使用的。