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    State of Observers — 28 February 2010

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    • AdamBA Offline
      AdamB
      last edited by

      @clarryr said:

      I am also looking at the reliability of the observer classes. So far I've found that the model passed to ModelObserver.onDeleteModel is wrong. When the model started I set model.name = "myname". On all the other methods I tested in ModelObserver I was able to see myname. Not so on onDeleteModel.
      Larry

      Yep. My understanding is that all delete methods are called after the fact. So the referenced object is toast by the time you are invoked.

      Furthermore, I believe most problems caused by Observers is hanging onto stale references to Ruby objects that have been deleted. If you create null (do nothing) Observers, they are benign.

      Adam

      Developer of LightUp Click for website

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      • C Offline
        clarryr
        last edited by

        @unknownuser said:

        Yep. My understanding is that all delete methods are called after the fact. So the referenced object is toast by the time you are invoked.

        Furthermore, I believe most problems caused by Observers is hanging onto stale references to Ruby objects that have been deleted. If you create null (do nothing) Observers, they are benign.

        Adam

        That's pretty much what I guessed. Unfortunately, the model reference passed in is not nil. It doesn't seem to reference anything but it doesn't compare equal to nil and it's not the active_model either. Ruby seems to be pretty good about detecting and reporting method calls on nil but I can see where having this mystery model reference might cause problems. Bottom line seems to be to clean up in onSaveModel and ignore onDeleteModel. I was trying to be a good citizen and remove all of my observers when the model was deleted but Sketchup doesn't seem to care or has already removed them.
        One thing I can do when onDeleteModel is called is I do know 'self', so if I need to I can track all of my other observers as instance variables of my model observer.
        Larry

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        • M Offline
          Malkomitch
          last edited by

          EntitiesObserver works well if you don't erase any entity inside the observer.
          Otherwise, it makes Sketchup crash in an ugly way.

          I'm not sure about EntityObserver but i think that's pretty much the same behavior.

          Thank you for the report

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          • thomthomT Offline
            thomthom
            last edited by

            @malkomitch said:

            EntitiesObserver works well if you don't erase any entity inside the observer.
            Otherwise, it makes Sketchup crash in an ugly way.

            I'm not sure about EntityObserver but i think that's pretty much the same behavior.

            Thank you for the report

            In my experience I found adding the observers to cause a delayed crash no matter what - even if I never modified the model. Just attaching it.

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

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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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