C++ Coding Standards: 101 Rules, Guidelines, and Best Practices

32. Be clear what kind of class you’re writing

Summary

Know thyself: There are different kinds of classes. Know which kind you are writing.

Discussion

Different kinds of classes serve different purposes, and so follow different rules. Value classes (e.g., std::pair, std::vector) are modeled after built-in types. A value class:

• Has a public destructor, copy constructor, and assignment with value semantics.

• Has no virtual functions (including the destructor).

• Is intended to be used as a concrete class, not as a base class (see Item 35).

• Is usually instantiated on the stack or as a directly held member of another class.

Base classes are the building blocks of class hierarchies. A base class:

• Has a destructor that is public and virtual ...