Swift 中的免费桥接和指针访问

Question

我正在将应用程序从 Objective-C 移植到 Swift，我需要使用以下方法：

CFStreamCreatePairWithSocketToHost(alloc: CFAllocator!, host: CFString!, port: UInt32, \
readStream: CMutablePointer<Unmanaged<CFReadStream>?>, \
writeStream: CMutablePointer<Unmanaged<CFWriteStream>?>)

旧的逻辑看起来像这样（几个网站似乎都同意）：

CFReadStreamRef readStream = NULL;
CFWriteStreamRef writeStream = NULL;
CFStreamCreatePairWithSocketToHost(NULL, (__bridge CFStringRef)(host), port, \
                                   &readStream, &writeStream);

NSInputStream inputStream = (__bridge_transfer NSInputStream *)readStream;
NSOutputStream outputStream = (__bridge_transfer NSOutputStream *)writeStream;

由于免费桥接，效果很好。然而，ARC 并不存在于“Swift-space”中，并且类型系统也发生了变化。

如何将我的流变成

CMutablePointer<Unmanaged<CFReadStream>?>, and
CMutablePointer<Unmanaged<CFWriteStream>?>

然后将它们转换回 NSStream 之后的子类 CFStreamCreatePairWithSocketToHost 称呼？

Answer 1

我让它工作了，这是我的代码：确保在某处保留连接类的引用:-)

class Connection : NSObject, NSStreamDelegate {
    let serverAddress: CFString = "127.0.0.1"
    let serverPort: UInt32 = 8443

    private var inputStream: NSInputStream!
    private var outputStream: NSOutputStream!

    func connect() {
        println("connecting...")

        var readStream:  Unmanaged<CFReadStream>?
        var writeStream: Unmanaged<CFWriteStream>?

        CFStreamCreatePairWithSocketToHost(nil, self.serverAddress, self.serverPort, &readStream, &writeStream)

        // Documentation suggests readStream and writeStream can be assumed to
        // be non-nil. If you believe otherwise, you can test if either is nil
        // and implement whatever error-handling you wish.

        self.inputStream = readStream!.takeRetainedValue()
        self.outputStream = writeStream!.takeRetainedValue()

        self.inputStream.delegate = self
        self.outputStream.delegate = self

        self.inputStream.scheduleInRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)
        self.outputStream.scheduleInRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)

        self.inputStream.open()
        self.outputStream.open()
    }

    func stream(stream: NSStream, handleEvent eventCode: NSStreamEvent) {
        println("stream event")
    }
}

Answer 2

我无法让其他人在该线程中提供的示例起作用。当然，他们编译了，但是一旦连接打开，他们就崩溃了。

然而，我在 WWDC 2014 讨论（以及 iOS 8 发行说明）中注意到，有一种新方法可以初始化 NSStream，以创建一对绑定的输入/输出流。

见下文：

var inputStream: NSInputStream?
var outputStream: NSOutputStream?

NSStream.getStreamsToHostWithName("localhost", port: 1234, inputStream: &inputStream, outputStream: &outputStream)

这消除了对尴尬的 CFStreamCreatePairWithSocketToHost 调用的需要，也消除了对非托管资源的需要。

Answer 3

我想出了如何去做。一些重要的注意事项：

1. CMutablePointers 如果您使用 & 运算符，将自动创建。
2. 您可以访问 T 在一个 Unmanaged<T> 和 .getUnretainedValue() 和 getRetainedValue() （似乎 .getUnretainedValue() 类似于 __bridge_transfer)
3. 选项会自动初始化为 nil.
4. 如果可选的是 nil 它将转化为 false 健康）状况。

到目前为止我已经（未经测试）：

var readStream: Unmanaged<CFReadStream>?
var writeStream: Unmanaged<CFWriteStream>?

CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, host, port, \
&readStream, &writeStream)

if (readStream && writeStream) {
    inputStream = readStream!.takeUnretainedValue();
    outputStream = writeStream!.takeUnretainedValue();
}

Answer 4

我正在使用 NSStream 类的 getStreamsToHostWithName 函数。它比 CFStreamCreatePairWithSocketToHost 更容易、更好

func initNetworkCommunication() {

print("connecting...")

let serverAddress = "gzoa.vps.infomaniak.com"
let serverPort = 1234

NSStream.getStreamsToHostWithName(serverAddress, port: serverPort, inputStream: &inputStream, outputStream: &outputStream)

self.inputStream!.delegate = self
self.outputStream!.delegate = self

self.inputStream!.scheduleInRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)
self.outputStream!.scheduleInRunLoop(NSRunLoop.currentRunLoop(), forMode: NSDefaultRunLoopMode)

self.inputStream!.open()
self.outputStream!.open()

}

Answer 5

Swift 3 版本的 CF 和 NS 代码。两者都适合我。

CF：

class Connection: NSObject, StreamDelegate {

private var inputStream: InputStream!
private var outputStream: OutputStream!

var connected = false

func connect(host: String, port: UInt32) {
    var readStream:  Unmanaged<CFReadStream>?
    var writeStream: Unmanaged<CFWriteStream>?

    CFStreamCreatePairWithSocketToHost(nil, host as CFString, port, &readStream, &writeStream)

    self.inputStream = readStream!.takeRetainedValue()
    self.outputStream = writeStream!.takeRetainedValue()

    if let inputStream = inputStream, let outputStream = outputStream {
        inputStream.delegate = self
        outputStream.delegate = self

        inputStream.schedule(in: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)
        outputStream.schedule(in: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)

        inputStream.open()
        outputStream.open()

        connected = true
    }
}

func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
    print("stream event, \(eventCode)")
}

}

NS：

class NSConnection: NSObject, StreamDelegate {

private var inputStream: InputStream?
private var outputStream: OutputStream?

var connected = false

func connect(host: String, port: Int) {
    Stream.getStreamsToHost(withName: host, port: port, inputStream: &inputStream, outputStream: &outputStream)

    if let inputStream = inputStream, let outputStream = outputStream {
        inputStream.delegate = self
        outputStream.delegate = self

        inputStream.schedule(in: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)
        outputStream.schedule(in: RunLoop.current, forMode: RunLoopMode.defaultRunLoopMode)

        inputStream.open()
        outputStream.open()
    }
}

func stream(_ aStream: Stream, handle eventCode: Stream.Event) {
    print("stream event, \(eventCode)")
}

}