It is important to be aware that STL containers use copy operations and to implement these operations as efficiently as possibly. When an object is added to a container it is copied and the copy is stored inside the container; for objects of class type this copy is made by the class copy constructor. For some container types, including vector, objects may be moved inside the container; this move will use the class copy assignment operator.

   
   class MyClass
   {
   public:
      MyClass();
      MyClass( MyClass const& rhs );              // copy ctor
      MyClass& operator=( const MyClass& rhs );   // copy assignment
   };
   
   void foo( const MyClass& obj, const MyClass& anotherObj )
   {
      std::vector< MyClass > vec;
   
      // Call to push_back will call the copy constructor.
      //
      vec.push_back( obj );
   
      // Call to insert will call the copy assigment operator for
      // each object stored after the insert iterator.
      //
      vec.insert( vec.begin(), anotherObj );
   }

Guideline 17.4

Effective STL Item 3;