On 5 July 2017 at 12:49, Murray Cumming <murr...@murrayc.com> wrote: > On Tue, 2017-07-04 at 09:44 +0100, Daniel Boles wrote: > > How/can I receive an event when some object of my choice is > > destroyed, so that I can take appropriate action? > > > > Here's an example I came up against lately. I should probably > > refactor the code so I don't need to do things this way... but it > > illustrates the question quite well. I have a ComboBox where, via > > some boring exposition, I want to put a signal_changed() handler on > > its StyleContext. However, that handler holds a reference to a row in > > the ComboBox's model. Therefore, I need to receive notification when > > that model dies (i.e. when all holders of RefPtrs release them), so > > that I can disconnect that signal_changed() handler and therefore > > stop it from trying to access a dead row. > [snip] > > This shouldn't generally happen. The sigc::trackable base class should > take care of this. Maybe it would be best to try to reduce this to a > simple test case. >
>From my limited understanding of trackable, the issue is probably that my handler was a lambda, not a sigc::mem_fun. I would prefer not to have to set the handler on an object, and be required to derive that object from sigc::trackable, but it sounds like there's not another way. Anyway, I rewrote the whole thing so that it works differently, and now I don't really need this handler... I was just curious how it might be done. Still interested if you have any suggestions!
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