1

Is there any way I can kill a thread spawn through:

[NSThread detachNewThreadSelector:@selector(serverFetchInThread) toTarget:self withObject:nil];

The scenario I am working on is that in my main thread I am letting user enter data in my search bar and what ever user is typing I need to send to server for searching in a separate thread. Now, if user changes his selection by deleting old data and entering new data I do not want the previous thread to waste its time, kill it and spawn a new thread with new data.

Be there any other better way to handle this situation, please guide me.

Abhinav
  • 37,684
  • 43
  • 191
  • 309

2 Answers2

3

No, there is no way to kill a thread from another thread. And for good reason as there is no way to do so in a fashion where the targeted thread is killed without risk of crashing the app.

To directly answer your question; you need to have some kind of a flag that indicates to the thread that it should stop doing whatever it is doing and exit.

However, a couple of questions are raised by your question:

First, why are you using threads and not using GCD? Concurrency via GCD or NSOperation is the generally recommended way to solve such problems.

Secondly, if you are talking to a server, are you using HTTP (most of the time, that is the case)? If so, why not directly use the asynchronous features of NSURL and friends?

bbum
  • 162,346
  • 23
  • 271
  • 359
  • Thank you. I am using async HTTP connection. Can you please throw some more light on using a flag and indicating the thread to stop itself. I will be setting up the flag in the main thread, right? How can I read that in separate thread. – Abhinav Mar 26 '11 at 19:31
  • NSHTTPConnection can be stopped just by calling it's `cancel` method. – peterjb Mar 26 '11 at 19:42
  • Thats right but once a asyc server call is made in a thread how can I call a cancel method on it from main thread. – Abhinav Mar 26 '11 at 20:39
  • Use a BOOL; either a global or an instance variable. Set it from the main thread and periodically check it in your background thread. Avoid polling, though. – bbum Mar 26 '11 at 22:01
  • However, if you are using NSHTTPConnection, then there is no need to spawn a thread to do the connection. – bbum Mar 26 '11 at 22:02
  • I don't see NSHTTPConnection, only NSURLConnection. – zaph Mar 27 '11 at 12:15
  • @CocoaFu: Yeah its NSURLConnection and bbum is right. We need not to spawn a Thread for making this connection. – Abhinav Mar 27 '11 at 16:09
1

Have a good look at using NSOperationQueue.

You can subclass NSOperation it to wrap up your server communications, and even make that queue serial (maximum operations = 1).

If a server operation is not yet finished and user has generated more input, you can cancel the existing one, and add the new one.

Due to the effect of the NSOperation wrapping your connection, you can just use the simple synchronous version and keep the connection handling very straightforward.

Also worth mentioning is compatibility. I would prefer to use GCD and blocks, but for compatibility, NSOperationQueue is required.

ohhorob
  • 11,695
  • 7
  • 41
  • 50