'map'生成[T]，而不是预期的上下文结果类型'UnsafeMutablePointer '('map' produces [T], no

'map'生成[T]，而不是预期的上下文结果类型'UnsafeMutablePointer '('map' produces [T], not the expected contextual result type 'UnsafeMutablePointer')

我用这个方法调用getLineDash的UIBeizerPath ：

path.getLineDash(pattern.map{CGFloat($0)}, ...)

pattern是[Float] （我必须使用[Float] ，而不是[CGFloat] ）下面的快速方法将[浮点]投射到[CGFloat]？ 把它投给[CGFloat] ，但是它给了我

Cannot convert value of type '[CGFloat]' to expected argument type 'UnsafeMutablePointer<CGFloat>?'

奇怪的是，表演

path.setLineDash(pattern.map{CGFloat($0)}, ...

不会引发编译错误。

在这个问题之后，我添加as UnsafeMutablePointer<CGFloat>但它仍然给我错误。

I am calling getLineDash of a UIBeizerPath with this:

path.getLineDash(pattern.map{CGFloat($0)}, ...)

Where pattern is a [Float] (And I must use [Float], not [CGFloat]) following Fast method to cast [Float] to [CGFloat]? to cast it to [CGFloat], but it is giving me

Cannot convert value of type '[CGFloat]' to expected argument type 'UnsafeMutablePointer<CGFloat>?'

Weirdly, performing

path.setLineDash(pattern.map{CGFloat($0)}, ...

Does not raise a compile error.

Following this question, I added as UnsafeMutablePointer<CGFloat> but it is still giving me the error.

最满意答案

我有点愚蠢。 我没有完全理解UnsafeMutablePointer 。

基本上它们都是inout参数，所以它们在函数调用之前需要＆符号（ & ）。 同样，因为它是inout，我必须将一个[CGFloat]变量传递给它。

此代码工作：

var pat = pattern.map{CGFloat($0)} var cou = count var phas = phase.map{CGFloat($0)} path.getLineDash(&pat, count: &cou, phase: &phas)

I was a bit stupid. I didn't fully understand UnsafeMutablePointers.

basically they are inout parameters, so they need the ampersand (&) before the function call. also, as it is inout, I must pass a variable of [CGFloat] to it.

This code worked:

var pat = pattern.map{CGFloat($0)} var cou = count var phas = phase.map{CGFloat($0)} path.getLineDash(&pat, count: &cou, phase: &phas)