Swift：如何在子进程中读取标准输出而无需等待进程完成

我有一个外部控制台应用程序(在OS X上),它发出一系列从1到100到标准输出的整数,大约每秒一次.

我Swift,我需要使用该数字流来更新进度指示器.

这是我到目前为止的代码：

class MasterViewController: NSViewController {

@IBOutlet weak var progressIndicator: nsprogressIndicator!

override func viewDidLoad() {
    super.viewDidLoad()

    let task = Process()
    task.launchPath = "/bin/sh"
    task.arguments = ["-c","sleep 1; echo 10 ; sleep 1 ; echo 20 ; sleep 1 ; echo 30 ; sleep 1 ; echo 40; sleep 1; echo 50; sleep 1; echo 60; sleep 1"]  

    let pipe = Pipe()
    task.standardOutput = pipe

    task.launch()

    let data = pipe.fileHandleForReading.readDataToEndOfFile()
    if let string = String(data: data,encoding: String.Encoding.utf8) {
        print(string)
    }
}

代码工作 – 也就是说,它从命令行实用程序读取输出并相应地修改进度指示器 – 但它在实用程序退出后进行所有更改(并使我的UI在此期间等待).

我如何设置它以便从后台应用程序读取输出并实时更新进度指示器？

UPDATE

为了将来的参考,以下是我最终如何使用它(现在为Swift 3更新)：

class ViewController: NSViewController {

    @IBOutlet weak var progressIndicator: nsprogressIndicator!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.


        let task = Process()
        task.launchPath = "/bin/sh"
        task.arguments = ["-c","sleep 1; echo 10 ; sleep 1 ; echo 20 ; sleep 1 ; echo 30 ; sleep 1 ; echo 40; sleep 1; echo 50; sleep 1; echo 60; sleep 1"]

        let pipe = Pipe()
        task.standardOutput = pipe
        let outHandle = pipe.fileHandleForReading
        outHandle.waitForDataInBackgroundAndNotify()

        var progressObserver : NSObjectProtocol!
        progressObserver = NotificationCenter.default.addobserver(
            forName: NSNotification.Name.NSFileHandleDataAvailable,object: outHandle,queue: nil)
        {
            notification -> Void in
            let data = outHandle.availableData

            if data.count > 0 {
                if let str = String(data: data,encoding: String.Encoding.utf8) {
                    if let newValue = Double(str.trimEverything) {
                        self.progressIndicator.doubleValue = newValue
                    }
                }
                outHandle.waitForDataInBackgroundAndNotify()
            } else {
                // That means we've reached the end of the input.
                NotificationCenter.default.removeObserver(progressObserver)
            }
        }

        var terminationObserver : NSObjectProtocol!
        terminationObserver = NotificationCenter.default.addobserver(
            forName: Process.didTerminateNotification,object: task,queue: nil)
        {
            notification -> Void in
            // Process was terminated. Hence,progress should be 100%
            self.progressIndicator.doubleValue = 100
            NotificationCenter.default.removeObserver(terminationObserver)
        }

        task.launch()

    }

    override var representedobject: Any? {
        didSet {
        // Update the view,if already loaded.
        }
    }

}


// This is just a convenience extension so that I can trim
// off the extra newlines and white spaces before converting
// the input to a Double.
fileprivate extension String {
    var trimEverything: String {
        return self.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)
    }
}

现在,进度条进展到60％,然后在子进程完成后跳转到100％.

您正在主线程上同步读取,因此在函数返回主循环之前不会更新UI.

有(至少)两种可能的方法来解决问题：

>在后台线程上从管道读取(例如通过将其分派到后台队列 – 但不要忘记
再次将UI更新分派给主线程).
>使用通知从管道异步读取(请参阅
以Real time NSTask output to NSTextView with Swift为例).