C++ vector of objects vs. vector of pointers to objects

Question

I am writing an application using openFrameworks, but my question is not specific to just oF; rather, it is a general question about C++ vectors in general.

I wanted

Answer 1

Usually I don't store classes directly in std::vector. The reason is simple: you would not know if the class is derived or not.

E.g.:

In headers:

class base
{
public:
  virtual base * clone() { new base(*this); };
  virtual ~base(){};
};
class derived : public base
{
public:
  virtual base * clone() { new derived(*this); };
};
void some_code(void);
void work_on_some_class( base &_arg );

In source:

void some_code(void)
{
  ...
  derived instance;
  work_on_some_class(derived instance);
  ...
}

void work_on_some_class( base &_arg )
{
  vector store;
  ...
  store.push_back(*_arg.clone());
  // Issue!
  // get derived * from clone -> the size of the object would greater than size of base
}

So I prefer to use shared_ptr:

void work_on_some_class( base &_arg )
{
  vector > store;
  ...
  store.push_back(_arg.clone());
  // no issue :)
}