Deleting an observer

kiesewetter

Hallo!

Is it possible to deactivate or delete an observer after the observer has been invoken? Ideally in the observer itself.

Thanks for your time.

TIG

I think an observer killing itself is a recipe for failure.

When you start an observer you couldn give it a global reference like $kieserwetter_observer that is not likely to clash with another global variable.
Then when you apply it to objects you can always attach the same observer [making a new observer each time will be impossible to keep track of].
Later if you want to remove an observer from an object you now have a handle [$kieserwetter_observer] to it... in any code at all you might run later...

Dan Rathbun

You should always be running your code within your OWN namespace, so using a global variable is NEVER needed. I use @@ module vars to hold references to observers.

YES you can write a method within your observer class that can remove itself. I do this sometimes, and it is really just a wrapper for the remove_observer() method.

This example assumes your using your Observer in a Singleton manner:

class MySelectionObs < Sketchup;;SelectionObserver

  @@watched = []

  def attach(selection)
    raise(TypeError,"argument is not a Sketchup;;Selection object.") unless selection.class==(Sketchup;;Selection)
    if selection.class==(Sketchup;;Selection) &&
       (not self.watching?(selection))
      selection.add_observer(self)
      @@watched << selection
    end
  end

  def dettach(selection)
    raise(TypeError,"argument is not a Sketchup;;Selection object.") unless selection.class==(Sketchup;;Selection)
    if selection.class==(Sketchup;;Selection) &&
       self.watching?(selection)
      selection.remover_observer(self)
      @@watched.delete(selection)
    end
  end

  def verify_watchlist()
    unless @@watched.empty?
      @@watched.delete_if {|e| e.class != Sketchup;;Selection }
      @@watched.delete_if {|e| !e.model.valid? }
    end
  end

  def watching()
    verify_watchlist()
    return @@watched.dup
  end

  def watching?(selection)
    raise(TypeError,"argument is not a Sketchup;;Selection object.") unless selection.class==(Sketchup;;Selection)
    verify_watchlist()
    return @@watched.include?(selection)
  end

  ### define your other callback methods ###

end # class

ONE BIG EXCEPTION : NEVER dettach (remove) observers within the onQuit() callback of an AppObserver subclass instance !! A BugSplat! will occur.