How I Pimpl

Pimpl.cpp

struct Data
{
  Data()
  {
  }
  
  ~Data()
  {
  }
  
  // NO methods - this is a pure data type
  
  // List of properties
  int x;
  void* resource;
};

// Local static for all implementation details
namespace
{
  // This would normally have to be in your class private section
  void Detail(Data* data)
  {
  }
}

// Limited boiler-plate
API::API()
{
  data = new Data();
}
API::~API()
{
  delete data;
}

void API::DoStuff()
{
  // Write most of the implementation in here, branching out to local statics
  // for any further detail implementations
  data->resource;
  data->x;
  
  // Chain to other functions
  Detail(data);
}

Pimpl.h

class API
{
public:
  // Use new/delete to control lifetime
  API();
  ~API();
  
  void DoStuff();

private:
  struct Data* data;
};