Do not use multiple inheritance. If you need the service of
several classes, use delegation. The only possible but highly
unlikely exception to this is if your class inherits from other pure
Have a comment before a class that explains its purpose. Perhaps the
class name is so clear that this is obvious. Then some commentary on
what you are up to.
Only add members and methods to a class if they make sense with regards
to the bullet above. If you find yourself unsure to where to hook a piece
of logic, rethink the class and surrounding classes’ purposes.
Class names and method names are to be descriptive of what they do.
Avoid generic overloaded names (e.g., write, add, ...) to make grep
easier (and maybe reading too).
Don’t put implementation details in the header unless the user of the
class needs to know them. Sometimes single line inline
implementations are good “documentation”.
Be aware than many methods in the codebase can throw a DBException. If a class should never
throw (e.g. can be called in a destructor), that should be clear.
Write unit tests for each class you create. If you can’t easily
write a unit test for the class, that is a strong hint it has way too
many external dependencies.
Do not create early hierarchies. An early hierarchy is a one where
there is only one type of derived class. If you need to separate
functionality, use delegation instead. In that case, make sure to
Default to making classes non-assignable and non-copyable. Use MONGO_DISALLOW_COPYING().