Question

I have got a virtual class basic_action. Class sippeers inherits class basic_action. To store instances of sippeers classes I’m using boost::ptr_list. Here’s code example:

boost::ptr_list<basic_action> ActionsList;
sippeers spclass;
ActionsList.push_back(&spclass);
basic_action *sp = ActionsList.front();

Here I create an instance of prt_list with pointers to instances of my basic_action classes.
Next I make new instance of my sippeers class.
Next I insert pointer to sippeers class into ptr_list.

The last string fails.

Cannot convert from ‘basic_action’ to
‘basic_action *’.

But there IS a basic_action * inside, not basic_action!

Answer 1

boost::ptr_list::front() returns a reference to the templated type, not a pointer.

So in this case it’s returning a basic_action&.

See the documentation here for ptr_sequence_adapter, from which ptr_list is derived.

So your code should read:

boost::ptr_list<basic_action> ActionsList;
sippeers spclass;
ActionsList.push_back(&spclass);
basic_action &sp = ActionsList.front();