ios - Swift 中 CGPoint 到 CGFloat 的转换类型错误

Question

   var _deltaTime = NSTimeInterval()

   var _pointsPerScndSpeed = Double()

   var bgVelocity: CGPoint = CGPointMake(_pointsPerScndSpeed, 0.0)

      //Cannot convert the expression's to type 'CGFloat'

     var amToMove:CGPoint = CGPointMake(bgVelocity.x * _deltaTime, bgVelocity.y * _deltaTime)

       //Could not find an overload for '*' that accepts the supplied Arguments

Answer 1

CGPoint 的成员具有 CGFloat 类型，它是 32 位上的 Float架构和 64 位架构上的 Double。Swift 不会隐式转换类型。您可以使用CGFloat在您的代码中保持一致，或添加显式强制转换:

var bgVelocity: CGPoint = CGPointMake(CGFloat(_pointsPerScndSpeed), 0.0)
var amToMove:CGPoint = CGPointMake(bgVelocity.x * CGFloat(_deltaTime), bgVelocity.y * CGFloat(_deltaTime))