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

Constructors.

Types of constructors

Destructors.

We will do this with the help of some examples.

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.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,

I will open it.

constructor.cpp

In this program we will perform the addition of two numbers using constructor.

Let me explain the code now.

#include <iostream>

using namespace std;

class Addition

int a, b ;

These are the private members of class Addition.

public

Addition(int, int)

The constructor has the same name as the class name.

We have passed two arguements here.

int add( )

For this we use a tilde sign followed by the destructors name.

return(a + b);

It returns sum of a and b.

Addition :: Addition (int a, int b)

a and b are private members.

To access the private members we use x and y.

Then we access the destructor.

In this we print Memory Deallocation.

int main()

Addition obj (3, 4);

Then we pass two values as 3 and 4.

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

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

The constructor that has arguments is called parameterized constructor.

Hence this one is a prameterized constructor

cout << “Sum is ” <<obj.add() <<“\n”

And we print the sum.

return 0;

Ctrl, Alt and T keys simultaneously

g++ const-dest.cpp -o cons

To execute

Type

./cons

g++ cons-dest.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

In this tutorial we learned,

Constructors.

eg. Addition

Default Constructor.

eg. Subtraction

Parameterized Constructor.

eg. Addition obj (3, 4);

Destructors

eg. ~Addition

Create a class named Division.

Create a constructor for the class.

Create a function divide which divides two given numbers.

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