Swift“无法使用类型为（（@lvalue CGFloat，$ T7）'的参数列表调用'-='

Question

Can someone please explain to me why I am getting this error message when I try to run this code:

let sprite = SKSpriteNode(imageNamed:"Spaceship")

sprite.xScale = 0.5
sprite.yScale = 0.5
sprite.position = location

self.addChild(sprite)

var dt: Float = 1.0/60.0

sprite.position.x -= 100.0*dt;

The error message appears on the last line by the way

Answer 1

you need to change dt to CGFloat because sprite.position.x have type of CGFloat

var dt: CGFloat = 1.0/60.0

in Swift, arithmetic operators require both operands have same type