Item 19: Treat Class Design as Type Design

Because a new class is a new type.

Aspects of a new class to consider:

• How should you create/destroy/allocate/deallocate it
• How should object initialization differ from assignment and differ from movement
• Does it support pass-by-value (also see copy constructor)
• Valid range of object values
• Will there be an inheritance graph?
• What explicit/implicit type conversion are allowed
• What operators and member functions make sense
• What standard functions should be disallowed?
• Which part is public/protected/private? Who are friends?
• What is the “undeclared interface”? (Meaning, guarantees of performance, exception safety, resource usage, etc.)
• How general is it? (Should you use template instead?)
• Is a new type really needed?