编辑代码

class TriangleAndSquare {
    var triangle: EquilateralTrlangle {
        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 = EquilateralTrlangle(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)