无法转换类型为'UnsafePointer< Double>'的值到预期的参数类型'UnsafePointer< _>' [英] Cannot convert value of type 'UnsafePointer<Double>' to expected argument type 'UnsafePointer<_>'

问题描述

我正在Swift中为OS X使用外部C库.我得到一个值cda，在C中它定义为double*(它是一个双精度数组的指针).

I'm working with an external C library in Swift for OS X. I get a value cda, which is defined in C as a double* (it is a pointer to a double array).

当导入Swift时，它会将类型识别为UnsafeMutablePointer.我正在尝试将此指针和计数转换为双精度数组.这是我正在使用的代码(假设arrlen是数组的正确计数):

When importing into Swift, it recognizes the type as UnsafeMutablePointer. I'm trying to convert this pointer and the count into a double array. Here's the code that I'm using (assume arrlen is the correct count of the array):

let doublearrptr = UnsafePointer<Double>(cda)
let xptarr = UnsafeBufferPointer<Double>(start: doublearrptr, count:arrlen)

但是，在编译此代码片段时，出现错误:

However, when compiling this code fragment, I get the error:

Cannot convert value of type 'UnsafePointer<Double>' to expected argument type 'UnsafePointer<_>'

我对Swift还是比较陌生，但是我可以肯定我无法转换为UnsafePointer<_>.我尝试转换为UnsafePointer<Void>，但是得到了相同的错误. Swift确实认识到cda是UnsafeMutablePointer<Double>.

I'm relatively new to Swift, but I'm fairly certain that I can't convert to UnsafePointer<_>. I tried converting to UnsafePointer<Void>, but that got the same error. Swift does recognize that cda is a UnsafeMutablePointer<Double>.

推荐答案

因此，尽管能够绕行，但我还是能够解决它.

So, I was able to solve it, albeit in a roundabout way.

我创建了一个新的函数convert并使用了它:

I created a new function convert and used it:

func convertArr<T>(count: Int, data: UnsafePointer<T>) -> [T] {

    let buffer = UnsafeBufferPointer(start: data, count: count)
    return Array(buffer)
}
...
let doublearrptr = UnsafePointer<Double>(cda)
let arr = convertArr(Int(shobjarrlen), data: doublearrptr)

由于某种原因，这可行，但原始语法却不行...

For some reason this works but not the original syntax...

我仍然愿意从为什么原来的语法无法正常工作获得答案.

I'm still open to getting answers from why my original syntax didn't work.

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