Cpp Coding Standards/CLSDESIGN
General hints for class design. Items referring to constructors, destructors, copying and allocation (of classes) reside in topic Class Construction, Destruction and Copying. Items referring to virtual classes in hierarchies reside in Hierarchies of Virtual Classes. Encapsulation related items are in topic Encapsulation.
Contents
Summary
One Responsibility
Give one class only one cohesive responsibility.
How to Inherit
Inherit to be reused, not to reuse. Else prefer composition over inheritance.
No Implicit Conversions
Make single argument constructors “explicit”. Be aware of default arguments. Do not provide operator TYPE() functions.
Specific new and delete
When you provide a class-specific new or delete with custom parameters, provide the corresponding new or delete as well. (Not doing this causes memory leaks.) If you provide one class specific new, this hides all other variants of new. So you probably want to provide also the three all of the standard forms of new (plain, nothrow and inplace).
Related Rules
- CLSINIT – all items
- CODEDOCU:ClassResponsibility
- ENC – all items
- HIERARCHY – all items
- IFC – all items
Explanations
One Responsibility
It is preferable to focus on one thing at a time. This avoids implementation problems with diverging requirements and allows easier learning for users and maintainers of the class.
Example
std::basic_string is a well known example of a class that wants to do too many things at once.
