swift - 如何在 Swift 5.0 中使用 withUnsafeBytes() 和 outputStream.write() 消除警告

Question

我在下面有以下功能，我无法摆脱编译警告。警告 = 'withUnsafeBytes' 已弃用:使用 withUnsafeBytes<R>(_: (UnsafeRawBufferPointer) throws -> R) rethrows -> R相反

我尝试了有关 withUnsafeBytes 的在线文档(包括 stackoverflow.com)，但是 withUnsafeBytes() 的糟糕文档与不寻常的函数 outputStream.write(需要 UnsafePointer)混合在一起使我无法理解必须如何传递指针，也$0 指的是什么。我知道 $0 是代码闭包的隐式参数，但我得到的代码没有明确列出闭包参数，我无法弄清楚 $0 是什么。

func sendMessage(message: String)
{
    // URL Encode the message
    let URLEncodedMem = UnsafeMutablePointer<UInt8>.allocate(capacity: message.utf8CString.count * 3 + 1)
    defer { URLEncodedMem.deallocate() }
    urlEncode( URLEncodedMem, message )
    let urlEncodedMsg = String( cString: URLEncodedMem )

    // Build the server message to send
    let strToSend = "GET /userInput.mtml?userInput=\(urlEncodedMsg) HTTP/1.1\r\n"
            +       "Host: \(hostName):\(hostPort)\r\n\r\n"
    let data = strToSend.data(using: .utf8)!

    _ = data.withUnsafeBytes { outputStream.write($0, maxLength: data.count) }  // Warning = 'withUnsafeBytes' is deprecated: use `withUnsafeBytes<R>(_: (UnsafeRawBufferPointer) throws -> R) rethrows -> R` instead
}   //  sendMessage

即使 Swift 使用 withUnsafeBytes 进行了其他更改，我也希望代码能够继续工作。

我怀疑问题可能是不支持 withUsafeBytes>？不确定？？

Answer 1

这将在 Swift 5 中编译而不会出错。

let strToSend = "GET /userInput.mtml?userInput=\(urlEncodedMsg) HTTP/1.1\r\n"
    +       "Host: \(hostName):\(hostPort)\r\n\r\n"
let data = strToSend.data(using: .utf8)!

_ = data.withUnsafeBytes { outputStream.write($0.bindMemory(to: UInt8.self).baseAddress!, maxLength: data.count) }

(您可以在 SO 中找到一些关于弃用旧 withUnsafeBytes 的文章。)

但在你的情况下，你可以简单地把它写成:

let strToSend = "GET /userInput.mtml?userInput=\(urlEncodedMsg) HTTP/1.1\r\n"
    +       "Host: \(hostName):\(hostPort)\r\n\r\n"

outputStream.write(strToSend, maxLength: strToSend.utf8.count)