Constant Member Function in C++
What is difference between constructor and destructor
| Constructor | Destructor |
| it is executed on creation of objectits job is inita class contain multiple constructorsit can have parameters | it is executed before deleting objectits job is deinita class contain only one destructorit cannot have parameters. |
Constant members in C++
Member of class can be declared as constants
Constant members are of 2 types.
Constant data member
Constant member function
Constant data member
The value of constant data member has never changed.
Constant data member must be initialized using constructor list
It is used to defined read only property of object
Constant Member Function Syntax
const data type datamember-name
syntax of init constant data members using construct list
constructor-name(): constant-datamember(value,constant-datamember(value)----
{
statements;
}
//wap to find area of circle
Example
# include <iostream.h>
class circle
{
float r;
const float pi;
public :
circle() : pi(3.147)
{
r=1.5;
}
void find_area()
{
float area=pi*r*r;
cout<<”\n Area is”<<area;
}};
void main()
{
circle circle1; // create a object by calling constructor
circle1.find_area();
}
Constant member function Example
//Finding simple interest :
#inlude<iostream.h>
#include<conio.h>
class simple_interest
{
float amt;
int time;
const float rate;
public :
simple_interest(float a, int l, float r): rate(r)
{
amt=a;
time=t;
}
float find_interest()
{
float si=(amt * rate *time)/100;
cout<<”\n simple interest”<<si;
}
}
void main()
{
simple_interest_cust1(5000,12,1.5);
simple_interest_cust2(7000,24,2.5);
cust1.find_intrest ();
cust2.find_intrest ();
}
Constant member function in C++
Constant member function is an accessory function which cannot modifying values of data members.
It perform constant operation.
syntax :
<return type> function-name(<parameters>)
constant
{
statements;
}
Constant member function Example
# incude<iostream.h>
class account
{
int accno;
char name[10];
char name[10]; // private data
float balance;
public :
void read(); //modifier(it modifying)
void print_details() const;
};
void accout:: read()
{
cout<<”\n input account no”;
cin>>accno;
cout<<”\n input customer name”;
cin>>name;
cout<<”\n input balance”;
cin>>balance;
}
void account :: deposit(float tamt)
{
balance=balance+tamt;
}
void accout :: print_details() const
{
cout<<”\n account no”<<accno;
count<<”\n customer Name”<<Name1;
cout<<”\n balance”<<balance;
}
void main()
{
account acc1;
acc1.read();
acc1.deposit(3000);
acc1.print_details();
}
o/p :
input account no