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    State of Observers — 28 February 2010

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    • M Offline
      Malkomitch
      last edited by

      Do you call the same observer several times?

      for example, if an AppObserver.onNewModel of your own call a new EntityObserver each time you perform a File>New, you'll stack the EntityObservers without removing the old one. Every methods trigger n times and it may cause unwanted issues.

      try to track your observers by storing them in a global variable, for example. And if you find some duplicates, use Sketchup.active_model.entities.remove_observer before calling a new one

      In my scripts, if i use observers, i'm used to call a little function "refreshObservers" of my own, triggered by AppObserver.onNewModel or AppObserver.onOpenModel, that flushes all the old observers and create new ones.

      I'm using an EntitiesObserver every day. This observer is designed to build and update a catalogue of everything drawn in or removed from sketchup. With onElementAdded and onElementRemoved, I never experienced any crash, excepted when I try to remove an entity inside the EntitiesObserver methods. It breaks the elementary rule: don't touch the collection you're watching in

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      • thomthomT Offline
        thomthom
        last edited by

        hmm... will have to look deeper into it again. but I mean to remember that even when I removed the observers I still got crashes... hm..

        Thomas Thomassen — SketchUp Monkey & Coding addict
        List of my plugins and link to the CookieWare fund

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        • AdamBA Offline
          AdamB
          last edited by

          @malkomitch said:

          try to track your observers by storing them in a global variable, for example. And if you find some duplicates, use Sketchup.active_model.entities.remove_observer before calling a new one

          Very good advice. Also remove_observer will accept without error an observer that is currently not attached - I always use the cliche of "remove followed by add" to ensure you have just 1 observer.

          Developer of LightUp Click for website

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          • J Offline
            Jim
            last edited by

            I just noticed the AppObserver onNewModel event fires even if you hit the Cancel button on the "Save changes" dialog.

            Hi

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            • fredo6F Offline
              fredo6
              last edited by

              Maybe the most efficient is to use a uniqueclass instance for ALL observers.
              The observer class does not even need to be typed (i.e. a subclass of the Sketchup observer classes), as there is no check done by the methods add_observer (like for the Tool classes).

              All callback methods have different names and the relevant information is always in the arguments, so that you have the context of the entities and objects you 'observe'.

              This unique instance can easily be maintained at module level.

              Fredo

              PS: it is a little bit misleading that the API documentation always shows examples with creationof new observer class everytime it is attached to an entity, like Sketchup.active_model.entities.add_observer(MyEntitiesObserver.new)

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              • thomthomT Offline
                thomthom
                last edited by

                @unknownuser said:

                PS: it is a little bit misleading that the API documentation always shows examples with creation of new observer class everytime it is attached to an entity, like Sketchup.active_model.entities.add_observer(MyEntitiesObserver.new)
                ❓

                Thomas Thomassen — SketchUp Monkey & Coding addict
                List of my plugins and link to the CookieWare fund

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                • J Offline
                  Jim
                  last edited by

                  I don't know if this is "right" or not, but here is my approach.

                  I created a global $jf_observers = {}
                  Then, create a single instance of the observers I need:

                  $jf_observers[;layers] = JF;;LayersObserver.new
                  

                  When I need an observer, I register a block of code:

                  $jf_observers[;layers].register(;onLayerAdded) { |layers, layer| do_something(layer) }
                  

                  At this point, the observer is attached if it isn't attached (an AppObserver is also created and attached because it needs to re-attach any other observers onNewModel and onOpenModel.)

                  But, there is only a single instance of each observer in existence. There are a handful of entity-specific observers that do not fall under the AppObserver control. But all of the model-level observers can.

                  Using this method, any developer can use an observer simply by registering a block of code to be executed on an event. .register returns an id so you can later .unregister(id) the event, too. The observers detach themselves when there are no more events in their queues. I don't really ever see a reason to detach the AppObserver - it can stay attach forever.

                  I am in the process of coding a "suit" of observers that behave in a similar fashion, but I am not really far enough to know if it is a viable or stable strategy; although I think it is a solid approach.

                  Hi

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                  • R Offline
                    RickW
                    last edited by

                    For my part, I created the SmustardAppObserver that allows plugins to add calls to the Observer instance. When an event is triggered, the observer will parse the list of calls.

                    RickW
                    [www.smustard.com](http://www.smustard.com)

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                    • thomthomT Offline
                      thomthom
                      last edited by

                      Updated to reflect finding of bugged events in SelectionObserver.

                      Thomas Thomassen — SketchUp Monkey & Coding addict
                      List of my plugins and link to the CookieWare fund

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                      • thomthomT Offline
                        thomthom
                        last edited by

                        There also seems to be some oddness with DefinitionsObserver. Event's unexpectedly triggering. At least in SU7.1.

                        SU6:

                        • Group/Component Creation: onComponentPropertiesChanged
                        • Paste: onComponentPropertiesChanged

                        SU7:

                        • Group/Component Creation: onComponentPropertiesChanged

                        • Paste:

                        • Before you place the component: onComponentRemoved and onComponentPropertiesChanged

                        • After: onComponentRemoved

                        • Ctrl+Move: onComponentRemoved

                        Not sure if the onComponentRemoved started triggering in SU7.0 or 7.1.

                        Thomas Thomassen — SketchUp Monkey & Coding addict
                        List of my plugins and link to the CookieWare fund

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                        • thomthomT Offline
                          thomthom
                          last edited by

                          InstanceObserver.onClose does not trigger - at least not under SU7.1.

                          Thomas Thomassen — SketchUp Monkey & Coding addict
                          List of my plugins and link to the CookieWare fund

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                          • K Offline
                            kwalkerman
                            last edited by

                            EntityObserver - (and possibly others)

                            it seems that OnEraseEntity is activated after onChangeEntity, which means that if the entity is erased, it can cause bugs for whatever you are trying to do with OnChangeEntity. If OnEraseEntity were activated first, you could create a simple boolean value:

                            def initialize
                            @still_here = true
                            end

                            def OnEraseEntity(entity)

                            whatever you want to do...

                            @still_here = false
                            end

                            def OnChangeEntity(entity)
                            if (still_here)

                            whatever you want to do...

                            end
                            end

                            This is a problem because the entity seems to be erased before OnChangeEntity is called, which means that doing something to the entity gives errors, but your observer doesn't know it until it gets through OnChangeEntity to OnEraseEntity.

                            --
                            Karen

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                            • thomthomT Offline
                              thomthom
                              last edited by

                              @kwalkerman said:

                              This is a problem because the entity seems to be erased before OnChangeEntity is called, which means that doing something to the entity gives errors, but your observer doesn't know it until it gets through OnChangeEntity to OnEraseEntity.

                              Yea - the Entity and Entities observers aren't easy to deal with. 😞

                              Thomas Thomassen — SketchUp Monkey & Coding addict
                              List of my plugins and link to the CookieWare fund

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                              • J Offline
                                Jernej Vidmar
                                last edited by

                                Hi guys,

                                seems like we have found new observer problem (MacOSX + SketchUp8). When InstanceObserver is attached to the Group and SketchUp is then exited, bugsplat window appears. If the model is saved before exiting SketchUp, no bugsplat window appears.

                                class TestObserver <  Sketchup;;InstanceObserver
                                	def onOpen(entity)
                                		p 'on called'
                                	end
                                
                                	def onClose(entity)
                                		p 'onClose called'
                                	end
                                end
                                # Select a Skethcup Group and call this method
                                # so the observer will be attached to the Group
                                def attach_observer
                                	group = Sketchup.active_model.selection[0]
                                	group.add_observer(TestObserver.new)
                                end
                                

                                Can anyone please confirm that?

                                It seems to be MAC OS X + SketchUp 8 specific problem, Windows version works OK, and SU 7 on Mac OS X too.

                                Cheers,
                                N78

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                                • thomthomT Offline
                                  thomthom
                                  last edited by

                                  I've not gotten around to test the InstanceObserver - but I'll see if I can test it this weekend.

                                  Thomas Thomassen — SketchUp Monkey & Coding addict
                                  List of my plugins and link to the CookieWare fund

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                                  • AdamBA Offline
                                    AdamB
                                    last edited by

                                    Yes, I can confirm its a repeatable bug on Mac OSX SketchUp 8.

                                    I've logged a very grumpy bug report with Google.

                                    Useful to know you can stop the crash by saving before exiting, but I am disappointed a bug like this could be missed. I know software has bugs in it etc, but this seems like any basic regression testing / smoke testing would flush this one out.

                                    Developer of LightUp Click for website

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                                    • S Offline
                                      spring.freediver
                                      last edited by

                                      Does the View.remove_observer method work in SU7.1?

                                      I have a tool that needs to turn a ViewObserver on and off.

                                      In tool methods that receive a view argument:
                                      I use "@observer = view.add_observer(MyViewObserver.new)" to turn it on;
                                      and "view.remove_observer(@observer)" to turn it off.

                                      view.remove_observer returns false, and the observer is not removed.

                                      I tried changing @observer to a class variable (@@observer), and it still did not work.

                                      Any ideas?

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                                      • thomthomT Offline
                                        thomthom
                                        last edited by

                                        hm... I have not tried to remove observers from view objects...

                                        btw - I am compiling a new observer list: http://forums.sketchucation.com/viewtopic.php?f=180&t=30793
                                        If you find new information not included in the list - can you please let me know so I can update the list?

                                        Thomas Thomassen — SketchUp Monkey & Coding addict
                                        List of my plugins and link to the CookieWare fund

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                                        • thomthomT Offline
                                          thomthom
                                          last edited by

                                          @spring.freediver said:

                                          Does the View.remove_observer method work in SU7.1?

                                          I have a tool that needs to turn a ViewObserver on and off.

                                          In tool methods that receive a view argument:
                                          I use "@observer = view.add_observer(MyViewObserver.new)" to turn it on;
                                          and "view.remove_observer(@observer)" to turn it off.

                                          view.remove_observer returns false, and the observer is not removed.

                                          I tried changing @observer to a class variable (@@observer), and it still did not work.

                                          Any ideas?

                                          Hang on... aren't you suppose to do it like this:
                                          @observer = MyViewObserver.new view.add_observer(@observer)
                                          ...
                                          view.remove_observer(@observer)

                                          ❓

                                          Thomas Thomassen — SketchUp Monkey & Coding addict
                                          List of my plugins and link to the CookieWare fund

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                                          • thomthomT Offline
                                            thomthom
                                            last edited by

                                            Yea - pretty sure so - because .add_observer also returns true/false . You need to keep a reference to the actual observer instance.

                                            Thomas Thomassen — SketchUp Monkey & Coding addict
                                            List of my plugins and link to the CookieWare fund

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