Swift中的免费桥接和指针访问

Question

我正在将一个App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,这很好用.但是,ARC在"Swift-space"中不存在,并且类型系统已经改变.

如何将我的流变成实例

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

然后NSStream在CFStreamCreatePairWithSocketToHost调用之后将它们转换回子类？

Answer 1

我得到了它的工作,这是我的代码:确保你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

我无法得到其他人在此主题中提供的示例.当然,他们编译了,但是一旦连接打开就会崩溃.

但是,我在WWDC 2014讨论(和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)

这消除了对笨拙的CFStreamCreatePairWithSocketToHost调用的需要,并消除了对非托管资源的需求.