1. What is Constructors?
3. when to use the constructors
4. Destructors
Constructors are categorized in 4 types
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3. when to use the constructors
4. Destructors
5. why
should we use destructors? However memory is released when the program
terminates?
6. Example program for default, parametrized and copy constructor
7. Example program for Destructor
6. Example program for default, parametrized and copy constructor
7. Example program for Destructor
What is member functions?
Constructor is a special member functions
, which is used to initialize the data into the object
Important points about constructors:
2.
Constructor will return nothing, not even void.
3.
If no such constructor is defined
then the compiler supplies a default
constructor.
4.
Constructors should be declared
in public section.
5.
Constructors cannot be inherited, though a
derived class can call the base class constructor.
6.
Like other C++ functions
Constructors can have default arguments.
7.
Constructors cannot be virtual.
8.
When
a constructor is declared for a class, initialization of class objects become
mandatory.
9.
Constructors
are the special member functions that
allow same name as that of the class name
10.
Constructors allow you to initialize the
values into a instances, variables of objects.
11.
Constructors are invoked when the
objects of class are created.
12.
Constructors can be overloaded.
13.
Constructors of class is invoked in two
ways
i.
explicitly
ii.
implicitly
Example1:
class A
{
private:
int m, n;
public:
A( ); //constructor declared
};
A: :A( ) //constructor defined; it has same
name as its class name; it has no return type.
{
m=0;
n=0;
}
Void main()
{
A a1;
}
Explanation of the above example:
When a class contains the
constructor like the defined above, it is guaranteed that an object created by
the class will be initialized automatically.
For example the declaration A aObj;
Object aObj is created. Not only creates the object but also initializes
its data members m and n to zero.
There is no need to write any
statement to invoke the constructor as we do with the normal member functions.
If a normal member function is
defined for zero initialization, we need to invoke this function (Constructor)
for each of the objects separately, and this would become inconvenient if there
are large numbers of objects.
The default constructor for class
A is A::A()
Example 2:
#include<iostream.h>
class Integer
{
private:
int i;
public:
void getdata()
{
cout<<”endl<<”enter any integer”;
cin>>i;
}
void setdata (int j)
{
i=j;
}
Integer() //0 argument (or) default constructor
{
}
Integer (int j) //single
parameter constructor
{
i=j;
}
void display()
{
cout<<endl<<”value
of i”<<i;
}
};
void main ()
{
Integer i1; //
zero argument constructor will be called.
Integer i2(10); // single argument constructor will be called.
}
Constructors
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