How to access elements of a polymorphic vector with a for?

Question

I have a base classe called StateDefinition and it has the following definition:

class StateDefinition
{
public:
    StateDefinition();
    virtual bool condition() { return false; }
    virtual void reach() {}
};

I have some derivated classes that override the condition and reach methods. I use a std::vector<StateDefinition*> m_stateMachine to store objects from the derivated classes. Then I am trying to access the elements as following:

for (auto state = m_stateMachine.begin(); state != m_stateMachine.end(); state++)
    {
        if (!state->condition())
        {
            state->reach();
            break;
        }
    }

But this code it is not compiling, I am gettig the following error:

error: member reference base type 'std::_Simple_types::value_type' (aka 'StateDefinitions *') is not a structure or union

So my question is: How to access elements of a polymorphic vector with a for?

Answer 1

state is an iterator and you use a vector of pointer, so you need to dereference one more time

for (auto state = m_stateMachine.begin(); state != m_stateMachine.end(); state++)
    {
        if (!(*state)->condition())
        {
            (*state)->reach();
            break;
        }
    }

---

Else an easier way is :

for (auto state : m_stateMachine) {
   if (!state->condition())
   {
       state->reach();
       break;
   }
}