Question

this question的解决方案不再适用于Swift 3.

不再有bytes Data的属性{以前为NSData。

let data = dataToWrite.first!
self.outputStream.write(&data, maxLength: data.count)

使用此代码，我收到错误：

Cannot convert value of type 'Data' to expected argument type 'UInt8'

如何在Swift 3中将Data写入NSOutputStream？

Answer 1

NSData有bytes属性来访问字节。 Swift 3中新的Data值类型有withUnsafeBytes() 相反，它使用指向字节的指针调用闭包。

这就是你将Data写入NSOutputStream的方式（不转换为NSData）：

let data = ... // a Data value
let bytesWritten = data.withUnsafeBytes { outputStream.write($0, maxLength: data.count) }

说明： withUnsafeBytes()是一种通用方法：

/// Access the bytes in the data.
///
/// - warning: The byte pointer argument should not be stored and used outside of the lifetime of the call to the closure.
public func withUnsafeBytes<ResultType, ContentType>(_ body: @noescape (UnsafePointer<ContentType>) throws -> ResultType) rethrows -> ResultType

在上面的电话中，自动推断ContentType和ResultType 编译器（作为UInt8和Int），另外做了 UnsafePointer()转换不必要。

outputStream.write()返回实际写入的字节数。通常，您应该检查该值。它可以是-1 if 写入操作失败，或写入时小于data.count 插座，管道或其他带流量控制的物体。

Answer 2

Martin R ，谢谢你的回答。这是完整解决方案的基础。这是：

extension OutputStream {

    /// Write String to outputStream
    ///
    /// - parameter string:                The string to write.
    /// - parameter encoding:              The String.Encoding to use when writing the string. This will default to UTF8.
    /// - parameter allowLossyConversion:  Whether to permit lossy conversion when writing the string.
    ///
    /// - returns:                         Return total number of bytes written upon success. Return -1 upon failure.

    func write(_ string: String, encoding: String.Encoding = String.Encoding.utf8, allowLossyConversion: Bool = true) -> Int {
        if let data = string.data(using: encoding, allowLossyConversion: allowLossyConversion) {
            var bytesRemaining = data.count
            var totalBytesWritten = 0

            while bytesRemaining > 0 {
                let bytesWritten = data.withUnsafeBytes {
                    self.write(
                        $0.advanced(by: totalBytesWritten),
                        maxLength: bytesRemaining
                    )
                }
                if bytesWritten < 0 {
                    // "Can not OutputStream.write(): \(self.streamError?.localizedDescription)"
                    return -1
                } else if bytesWritten == 0 {
                    // "OutputStream.write() returned 0"
                    return totalBytesWritten
                }

                bytesRemaining -= bytesWritten
                totalBytesWritten += bytesWritten
            }

            return totalBytesWritten
        }

        return -1
    }
}

Answer 3

只需使用此扩展程序（Swift 4）

extension OutputStream {
  func write(data: Data) -> Int {
    return data.withUnsafeBytes { write($0, maxLength: data.count) }
  }
}

对于InputStream

extension InputStream {
  func read(data: inout Data) -> Int {
    return data.withUnsafeMutableBytes { read($0, maxLength: data.count) }
  }
}

Answer 4

Data和NSData是Swift 3中的两个单独的类，Data没有bytes属性。

解决方案是将data定义为类型NSData

let data: NSData = dataToWrite.first!
self.outputStream.write(UnsafePointer<UInt8>(data.bytes), maxLength: data.length)

根据 Migrating to Swift 2.3 or Swift 3 from Swift 2.2 ：

迁移器会将NSData的大部分用途转换为新的值类型Data。但是，NSData上的某些方法对UnsafeMutablePointer进行操作，而Data上的相应方法使用UnsafeMutablePointer。（例如，NSData.getBytes（：length :)比Data.copyBytes（：length :)更容易接受。）作为提醒，不保证Swift类型的内存中布局。

将数据写入Swift 3中的NSOutputStream

4 个答案: