二元运算符“+=”不能应用于两个“CGPoint”操作数

Question

基本语法问题但是，我无法解决

func updateForeground(){
    worldNode.enumerateChildNodes(withName: "foreground", using: { node, stop in
        if let foreground = node as? SKSpriteNode{
            let moveAmount = CGPoint(x: -self.groundSpeed * CGFloat(self.deltaTime), y: 0)
            foreground.position += moveAmount
            if foreground.position.x < -foreground.size.width{
                foreground.position += CGPoint(x: foreground.size.width * CGFloat(self.numberOfForegrounds), y: 0)
            }    
        }
    })
}

第 foreground.position += moveAmount 和

行出错

foreground.position += CGPoint(x: foreground.size.width * CGFloat(self.numberOfForegrounds), y: 0)

每个人都说使用这个代码：

public func + (A: CGPoint, B: CGPoint) -> CGPoint {
     return CGPoint(x: A.x + B.x, y: A.y + B.y)
}

或；

像这样：

A.position.x += b.position.x
A.position.y += b.position.y

请帮忙...

Answer 1

未为 CGPoint 定义 + 运算符，因此您不能使用它或 +=。您已经找到了必须定义的正确功能，只需确保您实际使用它即可。您实际上可以更进一步，还可以为 CGPoint.

定义 += 运算符

extension CGPoint {
    public static func +(lhs:CGPoint,rhs:CGPoint) -> CGPoint {
        return CGPoint(x: lhs.x + rhs.x, y: lhs.y + rhs.y)
    }

    public static func +=(lhs:inout CGPoint, rhs:CGPoint) {
        lhs = lhs + rhs
    }
}

func updateForeground(){
    worldNode.enumerateChildNodes(withName: "foreground", using: { node, stop in
        if let foreground = node as? SKSpriteNode {
            let moveAmount = CGPoint(x: -self.groundSpeed * CGFloat(self.deltaTime), y: 0)
            foreground.position += moveAmount
            if foreground.position.x < -foreground.size.width {
                foreground.position += CGPoint(x: foreground.size.width * CGFloat(self.numberOfForegrounds), y: 0)
            }    
        }
    })
}

Answer 2

您想使用“+=” 运算符。

为此：

func updateForeground() {

    worldNode.enumerateChildNodes(withName: "foreground", using: { node, stop in
    if let foreground = node as? SKSpriteNode{
        let moveAmount = CGPoint(x: -self.groundSpeed * CGFloat(self.deltaTime), y: 0)
        foreground.position.x += moveAmount.x
        foregorund.postion.y += moveAmount.y

        if foreground.position.x < -foreground.size.width {
          foreground.position.x += foreground.size.width * CGFloat(self.numberOfForegrounds)
        }    
    }
})

二元运算符“+=”不能应用于两个“CGPoint”操作数

Binary operator ‘+=’ cannot be applied to two ‘CGPoint’ operands

cgpoint

swift