[wxruby-users] wxruby 1.9.9 menu - strange corruption

[Ridge Mcghee]

Alex Fenton wrote:
> Hi
> 
> Ridge Mcghee wrote:
>> I'm subclassing menus to add an extra tag.
>> However, after some repeated menu use, the menu
>> item becomes corrupted.  The more menu items
>> there are, the more quickly the menu item becomes
>> corrupted.
>>
>> It appears (speculation) that a garbage collector
>> or some memory reclamation code is at work that
>> reallocates the MyMenuItem and transforms it into
>> a MenuItem.
> 
> Hopefully I can explain. You're right that it's to do with garbage
> collection. When Ruby's GC runs, there's no reference anywhere to the
> MyMenuItems, so they're swept away and the ruby object is deleted. Next
> time find_item is called, there is no Ruby object matching the found
> MenuItem, so it is re-wrapped as an ordinary MenuItem.
> 
> This is expected behaviour - "info" type objects such as MenuItem are
> not preserved. I'll have a look whether there is a way to change this
> without causing crashes or leaking memory, but I would suggest that you
> find an alternate way round this:
> 
> 1) Keep a reference (eg in an Array or Hash as a member of MyMenu) to
> each menu item, perhaps setting this up as part of the addEntry method
> of MyMenu. This will preserve the items from GC.
> 
> 2) Override MyMenu#find_item to return a MyMenuItem, rather than an
> ordinary MenuItem.
> 
> hth
> alex

Thanks for your response.

   Good suggestion (1) and that is actually what I did to move forward.
   However, I consider it a work-around.  I welcome your explanations
   because I want to understand.

   Here's my view:
   As a developer, I don't want just the "native" superclass to work
   properly with the GC.  I want my sub-classes to work properly, too.
   (e.g., my sub-class should inherit the reference count or whatever
   to make it a fully-qualified class, huh?)  If I understood your
   message, the GC is making decisions based on the type (MenuItem).
   Isn't this just what an object-oriented system should *not* do?

   Some questions:
   Is this a generic ruby issue (or is it unique to wxruby)?

   What triggers the GC ?  (While testing, I found that the "rewrapping"
   occurred whether or not I called find_item.  Just repeatedly 
selecting
   the MyMenuItem, which triggered a menu_event and caused on_menu_event
   to be called, would result in the MyMenuItem being "rewrapped" as a
   MenuItem.  As such, over-riding MyMenu#find_item would not be 
expected
   to solve the problem.)

   I appreciate your offer to "have a look" and I'd be interested to
   know whatever you find out.

Cheers,
Ridge


-- 
Posted via http://www.ruby-forum.com/.