如何将Int附加到新的Data结构(Swift 3)

Question

随着NSMutableData我可以创建数组Int's或Float的和存储的磁盘.

protocol BinaryConvertible
{
    init()
}

extension Int : BinaryConvertible {}


struct Storage<T: BinaryConvertible>
{
let data = NSMutableData()

func append(value: T)
{
    var input = value
    data.append(&input, length: sizeof(T))
}

func extract(index: Int) -> T
{
    var output = T()
    let range = NSRange(location: index * sizeof(T), length: sizeof(T))
    data.getBytes(&output, range: range)
    return output
}
}

Swift 3有一种在引擎盖下Data使用的新型NSData.喜欢String和NSString.我无法弄清楚如何添加例如Double使用新方法.

append函数现在需要a UnsafePointer<UInt8>,但是你如何从一个Double或任何随机结构创建它？

Answer 1

使用指针是我在Swift中最不喜欢的事情之一,但它也提供了良好的学习体验.这对我有用:

struct Storage<T: BinaryConvertible>
{
    var data = Data()

    mutating func append(value: T)
    {
        var input = value
        let buffer = UnsafeBufferPointer(start: &input, count: 1)
        self.data.append(buffer)
    }

    func extract(index: Int) -> T
    {
        let startIndex = index * sizeof(T)
        let endIndex = startIndex + sizeof(T)

        var output = T()
        let buffer = UnsafeMutableBufferPointer(start: &output, count: 1)
        let _ = self.data.copyBytes(to: buffer, from: startIndex..<endIndex)

        return output
    }
}

var s = Storage<Double>()
s.append(value: M_PI)
s.append(value: 42)
s.append(value: 100)

print(s.extract(index: 0))
print(s.extract(index: 1))
print(s.extract(index: 2))