NSThread sleepfortimeinterval blocks main thread

Question

I want to simulate a communication with a server. As the remote server will have some delays I want to use a background thread that has on it

 [NSThread sleepForTimeInterval:timeoutTillAnswer];

The thread is created with NSThread sub classing and started ... However I noticed that sleepForTimeInterval is blocking the main thread... Why??? Isn't a NSThread a backgroundThread by default?

This is how the thread is created:

   self.botThread = [[PSBotThread alloc] init];
    [self.botThread start];

Further info: This is the bot thread subclas

- (void)main
{
    @autoreleasepool {
        self.gManager = [[PSGameManager alloc] init];
        self.comManager = [[PSComManager alloc] init];
        self.bot = [[PSBotPlayer alloc] initWithName:@"Botus" andXP:[NSNumber numberWithInteger:1500]];
        self.gManager.localPlayer = self.bot;
        self.gManager.comDelegate = self.comManager;
        self.gManager.tillTheEndGame = NO;
        self.gManager.localDelegate = self.bot;
        self.comManager.gameManDelegate = self.gManager;
        self.comManager.isBackgroundThread = YES;
        self.comManager.logginEnabled = NO;
        self.gManager.logginEnabled = NO;
        self.bot.gameDelegate = self.gManager;
        BOOL isAlive = YES;
        // set up a run loop
        NSRunLoop *runloop = [NSRunLoop currentRunLoop];
        [runloop addPort:[NSMachPort port] forMode:NSDefaultRunLoopMode];
        [self.gManager beginGameSP];
        while (isAlive) { // 'isAlive' is a variable that is used to control the thread existence...
            [runloop runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
        }



    }
}

- (void)messageForBot:(NSData *)msg
{
    [self.comManager didReceiveMessage:msg];
}

I want to call "messageForBot" from the main thread... also the background thread should call a method on the main thread to communicate.. The sleep for time intervail in inside the gManager object ....

Show how you're creating the thread, what it does and when you call `sleepForTimeInterval:` (which delays the current thread at the time it's called). — Wain, Aug 15 '13 at 09:31
That's how I'm creating the thread ... [self.botThread start]; ... That calls the NSThread subclass PSBotThread main method .. . — user1028028, Aug 15 '13 at 09:36
But what does it do? Where is the `sleepForTimeInterval` at? — Wain, Aug 15 '13 at 09:38
the thread uses an object that will receive the messages and return a result... the sleepForTimeInterval is inside this object — user1028028, Aug 15 '13 at 11:16

score 23 · Accepted Answer · edited Dec 02 '14 at 17:04

23

It blocks whatever thread sleepForTimeInterval is running on. Run it on another thread to simulate your server delay like this:

dispatch_queue_t serverDelaySimulationThread = dispatch_queue_create("com.xxx.serverDelay", nil);
dispatch_async(serverDelaySimulationThread, ^{
     [NSThread sleepForTimeInterval:10.0];
     dispatch_async(dispatch_get_main_queue(), ^{
            //Your server communication code here
    }); 
});

edited Dec 02 '14 at 17:04

Jason Fox

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answered Aug 15 '13 at 09:42

John

2,672
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I don't think this will work ... maybe the thread creatoin should be in the dispatch_async ? – user1028028 Aug 15 '13 at 11:17
I am using it and it works fine. I did the same thing to simulate network latency. The dispatch_queue_create already created another thread. The sleepForTimeInterval in dispatch_async will cause that thread to sleep. – John Aug 15 '13 at 16:30
To me it blocks main thread...If you can, help me with this question http://stackoverflow.com/questions/32910632/objective-c-freezed-gui-also-with-queue?noredirect=1#comment53652781_32910632 – volperossa Oct 03 '15 at 13:19

sbarow · Answer 2 · 2013-08-15T11:57:41.970

1

Try create a method in your thread class called sleepThread

-(void)sleepThread
{
   [NSThread sleepForTimeInterval:timeoutTillAnswer];
}

Then to make it sleep from your main thread

[self.botThread performSelector:@selector(sleepThread) onThread:self.botThread withObject:nil waitUntilDone:NO];

To send updated to your main thread from your bot thread.

dispatch_async(dispatch_get_main_queue(), ^{
    [MainClass somethinghasUpdated];
});

Side Note

To create the RunLoop I think all you need to do is

// Run the Current RunLoop
[[NSRunLoop currentRunLoop] run];

edited Aug 15 '13 at 11:57

answered Aug 15 '13 at 11:41

sbarow

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I don't need to make it sleep from the main thread... it should make itself sleep after receiving a message from the main thread – user1028028 Aug 15 '13 at 11:47
Okay so you want it to sleep in the method - (void)messageForBot:(NSData *)msg ? – sbarow Aug 15 '13 at 11:48
NO, that method will call another on one of the internal objects created in the main method ... there I need it to sleep ... without blocking the UI like it does now – user1028028 Aug 15 '13 at 11:56
Okay so your main thread will call messageForBot: that method will then call your comManager and that will then invoke the sleep. To call messageBot from the main thread do this [self.botThread performSelector:@selector(messageForBot:) onThread:self.botThread withObject:someDataObject waitUntilDone:NO]; – sbarow Aug 15 '13 at 12:00

score 0 · Answer 3 · answered May 05 '16 at 14:17

Swift:

let nonBlockingQueue: dispatch_queue_t = dispatch_queue_create("nonBlockingQueue", DISPATCH_QUEUE_CONCURRENT)
dispatch_async(nonBlockingQueue) {
    NSThread.sleepForTimeInterval(1.0)
    dispatch_async(dispatch_get_main_queue(), {
        // do your stuff here
    })
}

NSThread sleepfortimeinterval blocks main thread

3 Answers3

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