如何将UnsafeMutablePointer <Double>数组转换为Double数组？

Question

我已经创建了这样的数组

var outputReal = UnsafeMutablePointer<Double>.allocate(capacity: numeroDados)

现在，我需要将其转换为的数组Double。

我可以使用以下方式进行转换：

var newArray : [Double] = []

for i in 0..<n {
  newArray[i] = outputReal
}

但是我记得在页面上看到了另一种方法。

有任何想法吗？

Answer 1

细节

• Xcode 11.2.1 (11B500)、Swift 5.1

解决方案1

extension UnsafeMutablePointer {
    func toArray(capacity: Int) -> [Pointee] {
        return Array(UnsafeBufferPointer(start: self, count: capacity))
    }
}

溶液1的使用

var array = [3.9, 7.7, 11.1, 1.11, 1.02, 3.3, 3.9, 0]
let pointer = UnsafeMutablePointer<Double>.allocate(capacity: array.count)
pointer.initialize(from: &array, count: array.count)
print(pointer.toArray(capacity: array.count))

解决方案2

extension Array {
    init(pointer: UnsafeMutablePointer<Element>, count: Int) {
        let bufferPointer = UnsafeBufferPointer<Element>(start: pointer, count: count)
        self = Array(bufferPointer)
    }
}

溶液2的使用

var array2 = [3.9, 7.7, 11.1, 1.11, 1.02, 3.3, 3.9, 0]
let pointer2 = UnsafeMutablePointer<Double>.allocate(capacity: array.count)
pointer2.initialize(from: &array, count: array.count)
print(Array(pointer: pointer2, count: array.count))

Answer 2

首先创建一个UnsafeBufferPointer<Double>引用相同的内存区域。这样就Collection可以从该内存创建和初始化数组：

let bufPtr = UnsafeBufferPointer(start: outputReal, count: numeroDados)
let newArray = Array(bufPtr)

或者，首先分配一个UnsafeMutableBufferPointer（同时保留分配的内存的地址和大小）：

let numeroDados = 10

let outputReal = UnsafeMutableBufferPointer<Double>.allocate(capacity: numeroDados)
outputReal.initialize(repeating: 0.0)

let newArray = Array(outputReal)

在这两种情况下，值都将复制到数组的元素存储中，因此最终必须释放释放的内存。