Richard wrote:
According to "Exceptional C++" there are four common pimpl implementation types: " 1. All private data (but not functions) go in the impl 2. Put all private members into impl 3. Put all private and protected members into impl 4. Make pimpl entirely the class that impl would have been, and write pimpl as only the public interface made up entirely of simple forwarding functions (a handle/body variant)"
(It states that number 3 is "wrong".)
In variants 1 and 2 pimpl has the public and protected methods in it and their implementation. In variant 4 pimpl has forwarding functions. How do I add member functions and their implementation to your pimpl class?
What is discussed in exceptional C++ is the use of the pimpl idiom. The library does not implement any of these types, you do. The library just eases the underlying work with memory management, etc. Eg. A gameplayer class. Type 1: --------- .hpp: struct GamePlayer { void IncreaseLives(); void MoveTo( Vector3 _newPosition); private: boost::pimpl<struct GamePlayerValues> m_Values; }; .cpp struct GamePlayerValues { CMyIntegerType m_Lives; Vector3 m_Position; }; void GamePlayer::IncreaseLives() { m_Values->m_Lives ++; } void GamePlayer::MoveTo( Vector3 _newPosition) { m_Values->m_Position = _newPosition; } etc. In the gameplayer class we hide all our 'private' values. So when someone includes the hpp file they don't see that our 'lives' are stored in a special integer class, CMyIntegerType. This has several advantages: * When 'CMyIntegerType' changes only the cpp file needs recompiling thus potentially reducing compile times greatly. * You completely hide the content of 'GamePlayerValues' from all other than the cpp file. In case it's secret :) Also, I guess type 3 is 'wrong' because protected values should be visible to derived classes, and with the pimpl idiom you hide those values like explained above. Regards, Asger Mangaard