swift如何发送＆nil到func？

Question

func setupCircular(circularLayer:inout CAShapeLayer?){
    if (circularLayer == nil) {
        circularLayer = CAShapeLayer()
    }else{

    }
}
setupCircular(circularLayer: &nil)

怎么写？

Answer 1

您不能在Swift中将值用作inout参数。您需要创建一个CAShapeLayer类型的变量，将其赋值nil并将其用作函数的输入参数。

func setupCircular(circularLayer:inout CAShapeLayer?){
    if (circularLayer == nil) {
        circularLayer = CAShapeLayer()
    }else{

    }
}

var circ: CAShapeLayer? = nil
setupCircular(circularLayer: &circ)