NSRunLoop in python

Question

Created Feb ’18

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I'm trying to follow the advice in Apple's documentation for stopping an NSRunLoop:

"If you want the run loop to terminate, you shouldn't use 'run'. Instead, use one of the other run methods and also check other arbitrary conditions of your own, in a loop. A simple example would be:"

BOOL shouldKeepRunning = YES; /

NSRunLoop *theRL = [NSRunLoop currentRunLoop];

while (shouldKeepRunning && [theRL runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]]);

I'm having trouble translating that to python. It still runs forever. Noticeably, the process maxes out a core after the time interval is up.

from Cocoa import NSObject, NSSpeechRecognizer, NSRunLoop, NSDefaultRunLoopMode, NSDate 
shouldKeepRunning = True 
theFuture = NSDate.alloc().initWithTimeIntervalSinceNow_(10) 

class Controller (NSObject): 
     def init(self): 
          commands = [ "up", "down" ] 
          self.recognizer = NSSpeechRecognizer.alloc().init() 
          self.recognizer.setCommands_(commands) 
          self.recognizer.startListening() 
          self.recognizer.setDelegate_(self) 

     def speechRecognizer_didRecognizeCommand_(self, recognizer, command): 
          shouldKeepRunning = False 
          return command 

controller = Controller.alloc().init() 
loop = NSRunLoop.currentRunLoop() 
while shouldKeepRunning and (loop.runMode_beforeDate_(NSDefaultRunLoopMode, theFuture)): 
     pass

Also I'm not convinced I can retrieve the command from out of the class. Any thoughts? Thanks.

Boost

Answer 1

DTS Engineer OP

Apple

Feb ’18

NSSpeechRecognizer

is scheduling the call to

speechRecognizer(_:didRecognizeCommand:)

so that it runs on the main thread but does not activate any run loop source, which is why

run(mode:before:)

is not returning. One easy fix is to force the run loop to cycle using

perform(_:with:afterDelay:)

. A delay of 0.0 is documented to run the selector on the next run loop cycle, and that gets you out of

run(mode:before:)

and allows you to notice

shouldKeepRunning

being false.

I tested this with the Swift code below (sorry it’s not Python; my days of PyObjC hacking are not officially over).

Also I'm not convinced I can retrieve the command from out of the class.

Just have your

speechRecognizer_didRecognizeCommand_

method store the command in

self.recognizedCommand

, and then you can pick it up from

controller.recognizedCommand

after the

while

is done. If you have

init

set

controller.recognizedCommand

to

None

you can tell whether something was recognised or not.

The code below shows this, albeit in Swift.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

import Cocoa

var shouldKeepRunning = true

class Controller : NSObject, NSSpeechRecognizerDelegate {

    override init() {
        self.recognizer = NSSpeechRecognizer()!
        self.recognizedCommand = nil
        super.init()
        self.recognizer.commands = [ "up", "down" ]
        self.recognizer.delegate = self
        self.recognizer.startListening()
    }

    let recognizer: NSSpeechRecognizer
    var recognizedCommand: String?

    func speechRecognizer(_ sender: NSSpeechRecognizer, didRecognizeCommand command: String) {
        assert(Thread.isMainThread)
        NSLog("recognised: %@", command)
        self.recognizedCommand = command
        shouldKeepRunning = false
        self.perform(#selector(noop), with: nil, afterDelay: 0.0)
    }

    @objc
    func noop() {
        NSLog("noop")
    }
}

func main() {
    NSLog("done")
    let controller = Controller()
    let deadline = Date(timeIntervalSinceNow: 10)
    while shouldKeepRunning && Date() < deadline {
        NSLog(">run")
        RunLoop.current.run(mode: .defaultRunLoopMode, before: deadline)
        NSLog("<run")
    }
    NSLog("done")
    NSLog("controller.recognizedCommand: %@", controller.recognizedCommand ?? "n/a")
}

main()

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