Use Classes with Object-Oriented Programming in C

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Use Classes with Object-Oriented Programming in
C

• By Wayne Cheng

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Object-Oriented Programming

• Introduction
• Five Tenets
• Terminology
• The foundation of C Classes

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Introduction

• It is the name given to a specific paradigm in
  the field of programming.
• With objects we are creating pieces of code that
  can stand alone.
• You know the box has inputs and outputs but you
  dont know what is inside it.

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Five Tenets

• Encapsulation
• Data Abstraction
• Information Hiding
• Inheritance
• Polymorphism

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Encapsulation

• The goal is to bind data and the functions that
  operate on that data together in one object.
• The functions will be our interface while the
  data will be hidden in the black box.
• Classes in C bind data and functions together
  in objects.

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Data Abstraction

• The goal is to force users to interface with the
  objects functions rather than accessing data
  directly.
• Data is in the box.
• The user can not access the data, he/she must use
  the defined interface functions to manipulate the
  data.
• Public elements of class are accessible from
  outside of class.
• Private restricts access to these functions and
  data members to this class alone. (as default)
• Protected restricts access to these functions
  and data member to this class and its children.
  (Children are classes derived from the current
  class)

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Information Hiding

• The goal is to prevent the user from seeing how
  our functions are implemented and exactly what
  they do.
• All the user will see are function prototypes,
  but no actual implementation.
• Multiple file projects by storing each class
  implementation in its own file, we can compile
  and distribute them without allowing users to see
  the internals of functions.

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C Class definition

• The syntax for a class definition is
• class Class_Name public Member_Specificati
  on 1 Member_Specification 2 Member_Specif
  ication 3 private Member_Specification_n1 M
  ember_Specification_n2

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Inheritance

• It is a mechanism that allows us to include
  Parent class into a Child class.
• It just another name for the topic of derived
  classes.
• The goal is code reusability and extensibility.
• With it we can reuse code without having to cut
  and paste it out of our old programs.
• It is a major stepping stone on the path to
  polymorphism.

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Polymorphism

• The goal is to write generic code that can handle
  multiple objects in the same way.
• In code, we can pass multiple objects all as the
  same base object.
• It is refers to the ability to associate multiple
  meaning to one function name by means of a
  special mechanism known as Late Binding.
• We use class hierarchies to allow us to treat
  child classes as their parent class or
  grandparent, etc.

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Terminology

• Object A collection of related data and
  functions bound together.
• Method A function of an object.
• Message A call to an object method. The term
  message passing in reference to OOP you are
  dealing with method calls.
• Member A method or variable that is part of an
  object (or class).
• Association an object using another object that
  exists outside of the first. (Must pass by
  address or reference)
• Aggregation An object that contains another
  object.
• Generalization An object that publicly inherits
  its parent. (Inheritance)
• Instance variable of data type (class or
  struct).

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The foundation of C Classes

• The class is how we are able to implement OOP
  concepts in C.
• The class by itself gives us three of our five
  tenets OOP such are Encapsulation, Data
  Abstraction and Information Hiding.
• It is a technique used in binding functions to
  the data that they manipulate. (Encapsulation)
• It allows us to protect the data from the users
  direct manipulation. (Data Abstraction)
• It allows us to hide the implementation of
  functions from the user. (Information Hiding)
• It defines all its members to be private by
  default.

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Classes

• A class is a data type whose variables are
  objects
• The definition of a class includes
• - Description of the kinds of values of the
  member variables
• - Description of the member functions
• A class description is somewhat like a structure
  definition plus the member variables

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C Class Example

• Examine a stack class two functions and two
  pieces of data.
• Class stack
• Functions
• Push it will have one parameter and will
  return a Boolean value indicating success or
  failure. The data passed in will be placed at
  the into the stack at the top.
• Pop it will have one parameter, a reference,
  and will return a Boolean value indicating
  success or failure. The value of the reference
  will be set to the value at the top of the
  stack.
• Data
• The first element of data will be the stack
  itself.
• The second element of data will be called top and
  will mark the current position in the stack.

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C Class Code

• //////////////////////////////////////////////////
  ///
• //File IntStack.h
• // This is an integer stack class.
• //////////////////////////////////////////////////
  ///
• class IntStack
• public
• IntStack() //the class
  constructors
• int push(int) //the push function prototype
• int pop(int) //the pop function prototype
• private
• int stack10, top //the definition of calss
  variables

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Class Code

• ///////////////////////////////////////////////
• //File IntStack.cpp
• ///////////////////////////////////////////////
• include IntStack.h //Import class
  specification
• IntStackIntStack() //The constructor
• top -1
• int IntStackpush(int x) //The push function
  implementation
• if(top 9) return 0
• top
• stacktop x
• return 1
• int IntStackpop(int x) //The pop function
  implementation
• if(top -1) return 0
• x stacktop
• top--
• return 1

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Class Code

• /////////////////////////////////////////////
• //pgm.cpp
• /////////////////////////////////////////////
• include IntStack.h
• include ltiostream.hgt
• void main ( )
• IntStack stack
• int back
• for (int x 0 x lt 12 x)
• cout ltlt Pushing ltlt x ltlt
• cout ltlt (stack.push(x)?Success Fail) ltlt
  endl
• for (x 0 x lt 12 x)
• cout ltlt Poping
• (stack.pop(back)? (cout ltlt back) (cout ltlt
  Fail)) ltlt endl

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Questions ?