Why is 'nil' not compatible with 'UnsafePointer<CGAffineTransform>' in Swift 3?

问题

Trying to create a CGMutablePath() as such:

let path = CGMutablePath()
CGPathMoveToPoint(path, nil, 30, 0)

but the compiler keeps on giving me the following error: \'nil\' not compatible with expected argument type \'UnsafePointer<CGAffineTransform>\'. What am I doing wrong? I can\'t seem to find anything else online. (Yes I\'ve tried converting the Ints to CGFloats but it doesn\'t seem to make a difference.)

回答1:

Try this:

let path = CGMutablePath()
path.move(to: CGPoint(x: 30, y: 0))

CGPath APIs are now imported as instance methods in Swift 3. You can check them with Command-clicking on CGMutablePath. Or see the latest reference of CGMutablePath.

回答2:

I was getting this error when trying to draw inside a CGRect

This solved it for me:

 let framePath : CGMutablePath = CGMutablePath()
 framePath.addRect(frameRect)

I hope this saves you countless hours trying to solve this. :)

来源：https://stackoverflow.com/questions/39041888/why-is-nil-not-compatible-with-unsafepointercgaffinetransform-in-swift-3