[Boost-users] Array of smart pointers to base class

From: scott velasquez (scottv_at_[hidden])
Date: 2006-09-29 10:37:10

Here is what I desire to have in my GUI library as it pertains to boost:

1.  No raw widgt pointers.  Container functions should take a reference to a 
base class smart pointer type rather then accepting raw pointers of the base 
class type.
2.  Containers store an array of smart pointers of the base GUI widget type. 
This is needed because containers can contain many widget derived types.

I'm just showing the class code that matters; Normally, you would have 
constructors, destructors, access label, etc.

class OWidget;

class ODerivedWidget : public OWidget;

class OWidgetContainer : public OWidget
{
    public:

    void Add( boost::shared_ptr<OWidget>& widget )
   {
        mWidgets.pushback(widget);
   }

    std::vector<boost::shared_ptr<OWidget>>     mWidgets;
}

int main(void)
{
    OWidgetContainer root;

    // Works just fine since the types match
    boost::shared_ptr<OWidget>    base(new OWidget());
    root.Add(base);

    // Doesn't work since the Add() function can't convert ODerivedWidget
shared pointer to OWidget shared pointer type.
    boost::shared_ptr<ODerivedWidget>    derived(new ODerivedWidget());
    root.Add( derived);
}

Is this even possible?  I've read about boost::any and boost:variant and 
while that might solve my problem of storing smart pointers of differing 
types, it doesn't allow me to pass smart pointers of derived types.

Any ideas/suggestions would be GREATLY appreciated!

-scottv