swift - 无法将 "inout CGAffineTransform"类型的值转换为预期参数

Question

我试图让玩家在路径中改变方向，问题是每次运行应用程序时都会弹出错误“无法将“inout CGAffineTransform”类型的值转换为预期参数。 ”

 override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
   /* Called when a touch begins */

    if gameStarted == false {

        gameStarted = true
        moveClockWise()
        movingClockWise = true


        var myCircle : CGMutablePath! = CGPathCreateMutable()
        let newDx = player.position.x - self.frame.width / 2
        let newDy = player.position.y - self.frame.height / 2
        let newRad = atan2(newDy, newDx)
        let newPath = UIBezierPath(arcCenter: CGPoint(x:self.frame.width / 2, y: self.frame.height / 2) , radius: 170, startAngle: newRad, endAngle: newRad + CGFloat(M_PI * 4), clockwise: true)

        var mirroring = CGAffineTransformMakeScale(1.0, -1.0) // flip horizontal
        var mirrorPath : CGMutablePath! = CGPathCreateMutable()
        let finalPath = withUnsafeMutablePointer(&mirroring)//Here it tells me the error
        {
            CGPathAddPath(mirrorPath, UnsafeMutablePointer($0), newPath.CGPath!)
        }

        let newFollow = SKAction.followPath(mirrorPath, asOffset: false, orientToPath: true, speed: 200)
        player.runAction(SKAction.repeatActionForever(newFollow).reversedAction(),withKey:"followPath")


   }else  {
        player.removeActionForKey("followPath")
    }

       }

func moveClockWise(){

    let dx = player.position.x - self.frame.width / 2
    let dy = player.position.y - self.frame.height / 2

    let rad = atan2(dy, dx)

    path = UIBezierPath(arcCenter: CGPoint(x:self.frame.width / 2, y: self.frame.height / 2) , radius: 170, startAngle: rad, endAngle: rad + CGFloat(M_PI * 4), clockwise: true)

    let follow = SKAction.followPath(path.CGPath, asOffset: false, orientToPath: true, speed: 200)
    player.runAction(SKAction.repeatActionForever(follow).reversedAction(),withKey:"followPath")

}

Answer 1

我建议将您的代码更改为:

    var mirroring = CGAffineTransformMakeScale(1.0, -1.0) // flip horizontal
    var mirrorPath : CGMutablePath! = CGPathCreateMutable()
    CGPathAddPath(mirrorPath, &mirroring, newPath.CGPath)

    let newFollow = SKAction.followPath(mirrorPath, asOffset: false, orientToPath: true, speed: 200)
    player.runAction(SKAction.repeatActionForever(newFollow).reversedAction(),withKey:"followPath")

<小时/>

来自Apple的文档Interacting with C API's

Constant Pointers

When a function is declared as taking a UnsafePointer argument, it can accept any of the following:

• nil, which is passed as a null pointer.
• An UnsafePointer, UnsafeMutablePointer, or AutoreleasingUnsafeMutablePointer value, which is converted to UnsafePointer if necessary.
• A String value, if Type is Int8 or UInt8. The string will automatically be converted to UTF8 in a buffer, and a pointer to that buffer is passed to the function.
• An inout expression whose left-hand side operand is of type Type, which is passed as a pointer to the address of the left-hand side identifier.
• A [Type] value, which is passed as a pointer to the start of the array.

第四个项目符号告诉我们您可以发送 &mirroring对于期待 UnsafePointer<CGAffineTransform> 的参数.