# Calling a method in the context of a specific thread **URL:** \ **Category:** Ruby\ **Created:** [September 29, 2010, 3:23am UTC](https://www.ruby-forum.com/t/calling-a-method-in-the-context-of-a-specific-thread/195725 "2010-09-29T03:23:28Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [September 29, 2010, 3:23am UTC](https://www.ruby-forum.com/t/calling-a-method-in-the-context-of-a-specific-thread/195725/1 "2010-09-29T03:23:28Z")
Background: I am writing an FXRuby program. My question should be independent of FXRuby, though. FXRuby is a GUI for Ruby. If I understand some of the comments made here (and I probably don’t) [see subject: interpreter cannot enter in the context from another thread] it is a bad thing to attempt to run an FXRuby function in a non-main thread. So … I have a non-main thread that wants to display a message box (i.e. “call” FXMessageBox"). How can I invoke FXMessageBox in the context of the main thread? I can think of all sorts of ugly solutions. For instance: 1. Set some global\_variable indicating the task I want to perform in the main thread. 2. Do a thread.stop 3. have a timer in the main thread and have it dispatch based on global\_variable 4. save the return code of FXMessageBox in a thread local variable the not-main-thread 5. Do a thread.run to wake up the stopped not-main-thread. Ugly! ---
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [September 30, 2010, 8:14am UTC](https://www.ruby-forum.com/t/calling-a-method-in-the-context-of-a-specific-thread/195725/2 "2010-09-30T08:14:25Z")
On 09/29/2010 03:22 AM, Ralph S. wrote: > For instance: > > 1. Set some global\_variable indicating the task I want to perform in the main thread. > 2. Do a thread.stop > 3. have a timer in the main thread and have it dispatch based on global\_variable > 4. save the return code of FXMessageBox in a thread local variable the not-main-thread > 5. Do a thread.run to wake up the stopped not-main-thread. 1. Have a task queue which is read in the main thread. You can even store lambdas in there. Cheers robert ---
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [September 30, 2010, 2:27pm UTC](https://www.ruby-forum.com/t/calling-a-method-in-the-context-of-a-specific-thread/195725/3 "2010-09-30T14:27:18Z")
Robert, Thursday, September 30, 2010, 12:10:34 AM, you wrote: RK\> On 09/29/2010 03:22 AM, Ralph S. wrote: > > [Note: parts of this message were removed to make it a legal post.] > > Background: > > I am writing an FXRuby program. My question should be independent of FXRuby, though. > > FXRuby is a GUI for Ruby. > > If I understand some of the comments made here (and I probably don’t) [see subject: interpreter cannot enter in the context from another thread] it is a bad thing to attempt to run an FXRuby function in a non-main thread. > > So … I have a non-main thread that wants to display a message box (i.e. “call” FXMessageBox"). > > How can I invoke FXMessageBox in the context of the main thread? > > I can think of all sorts of ugly solutions. > > For instance: > > 1. Set some global\_variable indicating the task I want to perform in the main thread. > > 2. Do a thread.stop > > 3. have a timer in the main thread and have it dispatch based on global\_variable > > 4. save the return code of FXMessageBox in a thread local variable the not-main-thread > > 5. Do a thread.run to wake up the stopped not-main-thread. RK\> 6) Have a task queue which is read in the main thread. You can even RK\> store lambdas in there. Please explain more; a lot more. I am particularly confused how a task queue would work given that nothing in the main thread can block since that would stop FXRuby’s message pump. ---
**Author:** ![ralphshnelvar](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/e19adc/32.png) [@ralphshnelvar](https://www.ruby-forum.com/u/ralphshnelvar)\ **Post date:** [September 30, 2010, 3:17pm UTC](https://www.ruby-forum.com/t/calling-a-method-in-the-context-of-a-specific-thread/195725/4 "2010-09-30T15:17:05Z")
On Thu, Sep 30, 2010 at 2:26 PM, Ralph S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > > 1. Do a thread.run to wake up the stopped not-main-thread. > > RK\> 6) Have a task queue which is read in the main thread. You can even > RK\> store lambdas in there. > > Please explain more; a lot more. > > I am particularly confused how a task queue would work given that nothing in the main thread can block since that would stop FXRuby’s message pump. Actually I do not know RXRuby - I just answered based on the information in your posting. Maybe there is a queue in FXRuby that is regularly read from the main thread and which you can use. Actually you need to be able to interfere with FXRuby’s processing otherwise I don’t understand how you want to make option 1 work. Btw, a quick Google revealed this at the top of the list: [http://www.fxruby.org/doc/differences.html#d0e5063](http://www.fxruby.org/doc/differences.html#d0e5063) Kind regards robert