Difference between revisions of "Advanced-C++/C2/Constructor-And-Destructor/English"

Constructors.

Types of constructors

Destructors.

We will do this with the help of example.

Ubuntu Operating System version 11.10,

g++ Compiler version 4.6.1.

A constructor is a member function.

It has the same name as the class name.

Constructors cannot return values.

Constructor is automatically called when an object is created.

Types of Constructors are:

Parameterized Constructors.

Copy Constructors.

Default Constructors.

We will discuss about them in another tutorial.No details about destructors. Pls change the opening statement or provide an additional slide for destructors.

Destructors are used to deallocate memory.

They are called when an object is destroyed.

A destructor takes no arguments and has no return types.

I have already typed the code on the editor,

So i will open it.

constructor.cpp

Let me explain the code now.

#include <iostream>

using namespace std;

class Addition

int a, b ;

public

It allows the data to be accessible by the other parts of our program.

Addition(int, int)

A constructor has the same name as the class name.

We have passed two arguements here.

int add( )

return(a + b);

Addition :: Addition (int a, int b)

It is a member function of the class Addition.

Here we have passed two arguments.

int x and c-c++-constructors-&-destructors-c3-eng.odtint y.

a = x;

b = y;

And the value of y will be stored in variable b.

int main()

Addition obj (3, 4);

Here we pass two values as 3 and 4.

3 will be stored in x and 4 will be stored in y.

Which means a's value will be 3 and b's vaue will be 4.

cout << “Addition of a and b is ” <<obj.add() <<“\n”

Here we call the function add through the object obj.

return 0;

Ctrl, Alt and T keys simultaneously

g++ constructor.cpp -o cons

To execute

Type

./cons

g++ constructor.cpp -o cons

To execute

Type

./cons

Output

Sum is 7.

And

Memory Deallocation

Come back ot our program.

I have already typed the code.

Note that our filename is default.cpp

If a constructor is not declared in the class,

Then the compiler assumes a default constructor for the class.

This is our header file as iostream.

Highlight

class Subtraction

Then we a and b declared as public.

int sub(int a, int b)

return (a-b);

We have passed two arguments int a and int b.

This returns the subtraction of two numbers a and b.

Subtraction ();

Here we access the default constructor using the scope resolution operator.

int main()

int x;

In this we have defined a variable x.

Subtraction s;

x=s.sub(8,4);

And pass two arguments as 8 and 4.

Then the result is stored in variable x.

cout <<"Difference is "<<x<<"\n";

return 0;

This is our return statement.

Come back to our terminal.

g++ default.cpp -o def

Type

./def

g++ default.cpp -o def

Type

./def

Output

Difference is 4

Here you can see that we have passed the arguments within the function.

In this tutorial we learned,

Constructors.

eg. Addition

Parameterized Constructor.

eg. Addition obj (3, 4);

Destructors

eg. ~Addition

Default Constructor.

eg. Subtraction

Create a class named Division.

Create a constructor for the class

Create a function divide which divides two given numbers.

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