Re: Multiple inheritance and enable_shared_from_this

From: Jason Winnebeck (yg-boost-users_at_[hidden])
Date: 2003-07-18 12:47:08

Peter Dimov wrote:
> Multiple inheritance from concrete classes is just problematic, in more ways
> that just enable_shared_from_this not working. :-)

Yes I know that ;).  This is the only time I've done it and perhaps I've 
made a mistake.  I have a class Thread, so objects that are Threads 
inherit from Thread and something else sometimes.  I probably should 
have considered doing something like the Runnable interface from Java, 
espically since I modeled my API similarly to Java's Thread class.

What I do with shared_ptr, is that I have to enforce a "base" reference, 
so there is a map of threads where the references are stored.  This 
keeps the Thread instance alive while the Thread is running.  Thus when 
a Thread starts, its shared_ptr is needed.

>    static sptr create() {
>      sptr this_( new Base1() );
>      register(this_);
>      return this_;
>    }

I do keep that in mind.  I have done that in some places.

> In general, enable_shared_from_this is to be avoided. You only need it in
> some rare cases.

Hmm I thought it would be a good thing to have a lot of the classes 
provide a "getPointer" method.  Well actually I just realized that is 
pretty flat out moronic, because you need a shared_ptr to call the get 
function, unless you are given a reference (which does happen in the 
listeners as you suggested earlier).

Jason