5.3. Given to Caller

A simple model, where applicable, is to give the instances to the caller. It isn't widely useful, but it does find appeal in some circumstances. An example would be when implementing a container that is seldom traversed more than once, and whose elements occupy a large amount of memory and/or other resources. Maintaining copies in these circumstances is likely to be a wasted effort, so they can just be given to the caller. This model is therefore more efficient than the vouched-lifetimes model (see Listing 5.4).

Listing 5.4.

class EnvironmentVariable


{


// Accessors


public:


   . . .


  String const *GetValuePart(size_t index) const


  {


    String *item;


    if(index < m_cParts)


    {


      item = m_store.Load(index);


    }


    else


    {


      item = 0;


    }


    return item;


  }


// Members


private:


  int       m_cParts;


  DiskStore m_store;


};