Constructor overloading in C++ Language

Constructor overloading

Defining more than one constructor within class by changing -->Number of parameters -->Types of parameters -->Order of parameters is called Constructor Overloading in C++ Constructor is overloaded in order to extend functionality of existing constructor

Constructor Overloading Example

# include<iostream.h> class  stock { int*a; int size; int top; public: stack(); stack(int); void push(int); void pop(); } stack :: stack() { top=-1; size=5; q=new int[size]; } stack :: stack(int s) { size=s; top=-1; a=new int[size]; void stack :: push (int e) { if(top)>size-1; cout<<”\n stack is full”; else a[++top]=e; } void stack :: pop() { if(top<0) cout<<”\n stack is empty”; else cout<<”\n element is”<<a[top---]; } void main() { stack stack1; stack  stack2(3); stack1.push(0); stack1.push(20); stack1.pop(); stack2.push(60); stack2.push(70); stack2.push(); } o/p :  void push(int e) { if(top>>size-1) else a[++top]=e; } # include<iostream.h> #inlude<string.h> class string { char *s; int size; public : string(); string(int); void read_string(); void print_string(); }; string:: string() { size=10; s=new char[size]; } string:: string (int s1) { size=s1; s=new char[size]; } void string :: read-string() { cout<<”\n input any string”; cin>>s; } void string:: print_string() { cout<<”\n string is”<<s; } void main() { string string1; string string2[20]; string1.read_string(); string2.print_string(); string2.print_string(); }  

Copy Constructor

• If there is no copy constructor compiler provide copy constructor within class.
• Copy constructor is a parameterized construct have parameter within class
• Copy constructor is used to create an object by copying contexts of existing object
• It is used to create a copy of object

Copy Constructor Syntax constructor-name(class-name & red-name) { staments; { }

• If constructor having parameter of type class, it receive object.
• copy constructor receive reference of the object
• It is using method i.e shallow copy and also reference type.

  Copy Constructor Example # include<iostream.h> class date { int dd, MM,YY; public: data(int,int,int); date(date&)      //(copy constructor) void point_date(); }; date:: date(int d, int M, int Y) { dd=d; MM=M; YY=Y; } date:: date(date &d) { dd=d.dd; mm=d.MM; YY=d.YY; } void date:: print_date() { cout<<”]n” <<d<<”\t”<<mm<<”\t”<<yy; } void main() { date dob(10,10,2014); date cdob(dob); dob.print_date(); colob.print_date(); }  

// copy constructor

# include<iostream.h> # include<string.h> class strudent { int rno; char name[10]; public : student(int,char*); student(student &); void print_student(); }; student::student(int r,char *n) { rno=r; strcopy(name,s.name); } void student::print_student() { count<<”\n rollno”<<rno; cout<<”\n name”<<name; } void main() { student1 stud1(101,”RONO”); student1 stud2(stud1); stud1.print_student(); stud2.print_student();  

Destructor

Destructor is a special member function This member function get executed before destroying object.

Destructor Properties

Destructor name is same as class name and it is prefix with ~ operator It is without any return type not even void It is not having any parameters/ arguments A class contain only one destructor.

Destructor Syntax

~destructor-name() { statements; }

DestructorExample

# include <iostream.h> class alpha { int x; public : alpha() { cout<<”\n inside construtor”; } ~alpha() { cout<<”\n inside destructor”; } }; void main() { alpha  alpha1; } o/p : inside constructor(creating object) inside Destructor(Deleting object) Eg:   #include <iostream.h> class array { int *a; int size; public : array(int s) { size=5; a=new int[size]; } void read_elements() { cout<<”\n input elements”; for(int i=0;i<size;i++) cin>>a[i]; } void print_elements() { cout<<”\n elements are \n”; for(int i=0;i<size;i++) cout<<endl<<a[i]; } ~array() { cout<<”\n inside destructor”; delete a; void main() { array array1(5); array1.read_elements(); array1.print_elements(); }