不推荐使用M_P:请使用'Double.pi'或'.pi'获取正确类型的值并避免在Swift3.1中进行转换

使用Xcode 8.3.1将代码更新为Swift3.1时出现此错误

'M_PI'已弃用:请使用'Double.pi'或'.pi'获取正确类型的值并避免投射.

我的代码在下面,

let center     = containerShapeView.center
let startAngle = CGFloat(0.0)
let endAngle   = CGFloat(M_PI*2)
let radius     = containerShapeView.bounds.width * 0.21

CGFloat(M_PI*2)行给出错误

我该如何解决？

好吧,请按照错误消息的说明操作:

let center     = containerShapeView.center
let startAngle = CGFloat(0.0)
let endAngle   = CGFloat(Double.pi) * 2
let radius     = containerShapeView.bounds.width * 0.21

或者更好的是,避免不必要的转换:

let center     = containerShapeView.center
let startAngle: CGFloat = 0
let endAngle   = CGFloat.pi * 2
let radius     = containerShapeView.bounds.width * 0.21