从 NSData 对象在 Swift 中创建一个数组

发布于07月02日

我正试图将一个整数数组存储到swift中的磁盘中.我可以将它们放入NSData对象中进行存储，但将它们重新放入数组中是很困难的.我可以用data.bytes获得原始数据COpaquePointer，但找不到用该指针初始化新swift数组的方法.有人知道怎么做吗？

import Foundation

var arr : UInt32[] = [32,4,123,4,5,2];

let data = NSData(bytes: arr, length: arr.count * sizeof(UInt32))

println(data)  //data looks good in the inspector

// now get it back into an array?

推荐答案

您可以使用NSData中的getBytes方法:

// the number of elements:
let count = data.length / sizeof(UInt32)

// create array of appropriate length:
var array = [UInt32](count: count, repeatedValue: 0)

// copy bytes into array
data.getBytes(&array, length:count * sizeof(UInt32))

print(array)
// Output: [32, 4, 123, 4, 5, 2]

Update for Swift 3 (Xcode 8): Swift 3有一个新的struct Data型

Array to Data:

var arr: [UInt32] = [32, 4, UInt32.max]
let data = Data(buffer: UnsafeBufferPointer(start: &arr, count: arr.count))
print(data) // <20000000 04000000 ffffffff>

Data to Array:

let arr2 = data.withUnsafeBytes {
    Array(UnsafeBufferPointer<UInt32>(start: $0, count: data.count/MemoryLayout<UInt32>.stride))
}
print(arr2) // [32, 4, 4294967295]

Update for Swift 5:

Array to Data:

let arr: [UInt32] = [32, 4, UInt32.max]
let data = Data(buffer: UnsafeBufferPointer(start: arr, count: arr.count))
print(data) // <20000000 04000000 ffffffff>

Data to Array:

var arr2 = Array<UInt32>(repeating: 0, count: data.count/MemoryLayout<UInt32>.stride)
_ = arr2.withUnsafeMutableBytes { data.copyBytes(to: $0) }
print(arr2) // [32, 4, 4294967295]