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(C++) class

Keyword to start a class declaration. A class is a user-defined type with multiple elements and access levels.

The class keyword also be used to create a template function.

Example class

class MyClass

{

public: int mValue;

};

int main()

{

MyClass m;

m.mValue = 10;

}

Don't forget the semicolon at the end of the class definition!

Table of contents

(C++) class 1

Example class 1

Table of contents 1

Class elements 1

Class access levels 2

Class types 3

Class design 3

Example classes 3

References 3

Class elements

A class can have member functions, member data, member constants, and member types.

struct MyClass

{

//public by default

void SetX(const int x) { m_x = x; } //A member function

int m_x; //A member variable

};

All classes have a (default-constructed) constructor, destructor, copy constructor and copy-assignment operator:

struct NoClass {}; //Do all classes really have a constructor, destructor,

//copy constructor and copy-assignment operator?

This class called NoClass is silently converted by your compiler to the following (from [0]).

struct NoClass

{

NoClass() //Default constructor

{

//something

}

NoClass(const NoClass& rhs) //copy constructor

{

//something

}

~NoClass() //Default destructor

{

//something

}

NoClass& operator=(const NoClass& rhs) //copy-assignment operator

{

//something

}

};

Know what functions C++ silently writes and calls [0].

Class access levels

A class has three different access levels: public, private and protected. A class' default for functions and variables is private. This is the only (!) difference with a struct, which has public as its default access level.

struct MyClass

{

//public by default, so the keyword public below is redundant

public : int m_public;

protected: int m_protected;

private: : int m_private;

};

int main()

{

MyClass m;

m.m_public = 0; //OK, this member variable is public

m.m_protected = 0; //Not allowed, this member variable is protected

m.m_private = 0; //Not allowed, this member variable is private

}

Class types

Specific class types are an abstract base class, a base class, a derived class, a functor and a template class.

Class design

See class design for some guidelines on class design.

Design patterns are standarized class designs to achieve a certain goal, often involving multiple classes.

Example classes

* Canvas

* DllHandle

* SharedObjectHandle

References

[0] Scott Meyers. Effective C++ (3rd edition).ISBN: 0-321-33487-6. Item 5: 'Know what functions C++ silently writes and calls'

Go back to Richel Bilderbeek's C++ page.

Go back to Richel Bilderbeek's homepage.