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Circular Referencing to COM Objects

Last post was 21 Feb 2003 at 03:52
Tags: United Kingdom
This is a comment thread discussing Circular Referencing to COM Objects
  • 9 years ago

    This thread is for discussions of Circular Referencing to COM Objects.

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  • 6 years ago

    very interesting and usefull trick. (I should have thought about it myself)

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  • 5 years ago

    I struggled for a long time with my app hanging after it quits.  It turned out to be a circular reference in the (approximately) 180 000 objects.


    Thnx for the great explanation and work-around.  Everything going smoothly again.


    igitur

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  • 5 years ago

    Glad it helped.

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  • 5 years ago

    I have a project with Splitter controls that require references to pairs of controls that are proportionally resized by the user.
    The application GPF's (occasionally) upon termination. If run inside a browser, it causes an error report and the browser stays in memory.
    I realize that setting the controls reference to Nothing during the Usercontrol_Terminate event would solve the problem, but your article explains why this was not happening. So that is good.
    Your solution is intriguing, but I would like to ask you if another solution might work.
    How about we reduce the refrence count on the objects in the Initialize routine? Like this:


    Private Sub UserControl_Initialize()
       Set Splitter1.LeftCtl = LeftThing
       Set Splitter1.RightCtl = RightThing


       ReduceRefrenceCountByOne LeftThing
       ReduceRefrenceCountByOne RightThing
    End Sub


    Now the Controls will be come out of memory as we really want when the parent control terminates. Incidentally, their UserControl_Terminate events will fire correctly too.


    Perhaps you have written the code to do the evil reference count manipulation?


    What do you think?


    G.

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  • 5 years ago

    There is no secret as to how you decrease the reference count of a COM object.  All you have to do is call the Release method of the IUnknown interface.  But VB will hide this.  However, you can cheat by creating or using a type library that does define the IUknown interface.  Then you could just do something like this:

    Code:
    Private Sub UserControl_Initialize()


    dim oObject as IUnknown


      Set Splitter1.LeftCtl = LeftThing
      Set Splitter1.RightCtl = RightThing


      set oObject = LeftThing
      oObject.Release
      set oObject = Nothing
      set oObject = RightThing
      oObject.Release
      set oObject = Nothing
    End Sub
    That should take care of it.  However, this method is somewhat cumbersome and can be easily avoided by soft referencing.  I say go with soft referencing.

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  • 5 years ago

    Great tutorial.This will definitely change the way i look up on these Matters..

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