Clamp node to screen bounds

Question

 override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {

        for touch: AnyObject in touches {
            let location = touch.locationInNode(self)
            let previousLocation = touch.previousLocationInNode(self)

            var translation = CGPointMake(location.x - previousLocation.x, location.y - previousLocation.y)
crossHair.position = CGPointMake(crossHair.position.x  + translation.x * 3, crossHair.position.y + translation.y * 3)
   }
    }

I have a crosshair on the screen and i can move it using touchesmoved as shown above, but my problem is i don't know how to prevent it from going of the screen. there is the fmaxf & fminf but i am not entirely sure how to use them, any help would be much appreciated.

Answer 1

You can limit the node inside the coordinates using the following code. The following code only checks if the position of the sprite is within the bounds. I assumed the position is at the centre of the sprite.

override func touchesMoved(touches: NSSet, withEvent event: UIEvent) {

    for touch: AnyObject in touches {
        let location = touch.locationInNode(self)
        let previousLocation = touch.previousLocationInNode(self)

        var translation = CGPointMake(location.x - previousLocation.x, location.y - previousLocation.y)
        var positionX : CGFloat = crossHair.position.x + translation.x * 3
        var positionY : CGFloat = crossHair.position.y + translation.y * 3

        if positionX < 0 {
            positionX = 0
        }
        else if positionX > self.size.width
        {
            positionX = self.size.width
        }

        if positionY < 0 {
            positionY = 0
        }
        else if positionY > self.size.height
        {
            positionY = self.size.height
        }

        crossHair.position = CGPointMake(positionX, positionY)

    }
}