Example of type erasure with C++ templates

type_erasure.cc

class Base {
public:
  Base* interface_method(...) {
    // this function could read in a file, and based on a 
    // a string determine the type that needs to be used
    // and then the builder is set using set_builder<T>()
    
    // now, internally you can use builder->build(...) to 
    // build the child that you want
    
    // however, if you would like to store a different 
    // specialized container for data, then you will 
    // need in addition to use the Curiously Recursive 
    // Template Pattern (CRTP) so that you may define 
    // methods in a base class which interact with the 
    // child classes members by name (irrespective of type).
    // An example of this can be found in my CRTP gist
    // https://gist.github.com/csullivan/8ce2311fa72cdc947958b3db786ac54d#file-crtp-cc-L13
  }

private:
  template<typename T> 
  void set_builder() { builder = new Builder_Impl<T>(); }

  // helper type erased classes
  struct Builder {
    virtual Base* build(...) = 0;
  };

  template<typename Child>
  struct Builder_Impl : Builder {
    virtual Base* build(...) {
      // some function that can make Child objects given the input arguments
      return make_derived_class<Child>(...); 
    }
  }
private:
  Builder* builder;
};