Question

   vector<Foo*>&         getVectorOfFoo();

I want to provide a list of my Foo objects to others. Is this the best way to do it? I am returning a reference here and not copying correct?

The caller could (accidentally) modify this list right? Is there a way to avoid this possibility? Could I return const vector ? But they could always modify the Foo objects as well and not much I can do there. 10-20 different people will be writing code that use this list of Foo.

Answer 1

First don’t return a list of pointers.
That makes it doubly unclear about the allowed actions.

Boost has a solution (as usual).
Return a pointer container. This exposes the pointers as normal members.

boost::ptr_vector<Foo> const&  getVectorOfFoo();

Now the user can not alter the returned vector.

Example:

#include <boost/ptr_container/ptr_vector.hpp>

class Foo
{
    public:
        void plop()         {}
        void poop() const   {}
};

boost::ptr_vector<Foo> const&  getVectorOfFoo()
{
    static boost::ptr_vector<Foo>  instance;  // Create and fill container with FOO objects.
    instance.push_back(new Foo);
    return instance;
}

int main()
{
    boost::ptr_vector<Foo> const&  value = getVectorOfFoo();  

    value[0].plop();  // Fail. not a const method (comment out this line)
    value[0].poop();
}