[zt] Uwyn C++ Coding Standard

Chapter 4. Class Design

Table of Contents

Required Class Methods

Class Layout

Initialize all Variables

Accessor Styles

Class Documentation

Required Class Methods

Tobe good citizens almost all classes should implement the followingmethods. If you don't have to define and implement any of the"required" methods they should still be represented in your classdefinition as comments. If you just let the compiler generate themwithout indicating through comments that you know that this is theintended behaviour, people might wonder about the possibility of anommision or oversight.

Details

Default Constructor

Ifyour class needs a constructor, make sure to provide one. You need oneif during the operation of the class it creates something or doessomething that needs to be undone when the object dies. This includescreating memory, opening file descriptors, opening transactions etc.

If the default constructor is sufficient add a comment indicating that the compiler-generated version will be used.

Ifyour default constructor has one or more optional arguments, add acomment indicating that it still functions as the default constructor.

Virtual Destructor

Ifyour class is intended to be derived from by other classes then makethe destructor virtual. You should always make a destructor virtual forthe sake of future extensibility. Only make it non virtual if you'vegot a real good reason to do so.

Copy Constructor

Ifyour class is copyable, either define a copy constructor and assignmentoperator or add a comment indicating that the compiler-generatedversions will be used.

If your classobjects should not be copied, make the copy constructor and assignmentoperator private and don't define bodies for them. If you don't knowwhether the class objects should be copyable, then assume not until thecopy operations are needed.

Assignment Operator

Ifyour class is assignable, either define a assignment operator or add acomment indicating that the compiler-generated versions will be used.

Ifyour objects should not be assigned, make the assignment operatorprivate and don't define bodies for them. If you don't know whether theclass objects should be assignable, then assume not.

Justification

• Virtualdestructors ensure objects will be completely destructed regardless ofinheritance depth. You don't have to use a virtual destructor when:
  • You don't expect a class to have descendants.
  • The overhead of virtualness would be too much.
  • An object must have a certain data layout and size.
• A default constructor allows an object to be used in an array.
• Thecopy constructor and assignment operator ensure an object is alwaysproperly constructed. Making them private, prevents copies from objectsbeing made without you knowing about it and thus possibly inducing anunnecessary overhead or cause for inconsistency.

Example 4-1. Required Class Methods Example

class Planet
{
public:
    // Planet();
    Planet(int radius= 5);
    ~Planet();
    
private:
    Planet(const Planet&);
    Planet& operator=(const Planet&);
};