1. Overloaded Constructors and Multiple Classes
OOP
Overloaded Constructors and Multiple Classes
Malik Jahan Khan
Malik Jahan Khan

2. OOP
Overloaded Functions
We may have many functions in the same program having same function name but different number of arguments
They are differentiated by the number of arguments passed while calling them from main()
Such functions are called overloaded functions
Malik Jahan Khan

3. Constructors having Arguments
Some times, we need to specify default initialization values at the time of object creation
This can be done by passing arguments to constructors
In this way, each object may be initialized through constructor with a different value

4. Example
#include<iostream> using namespace std; class Person { private: int id; public: Person(int d) : id(d) } void showID() cout<<"\n My ID is "<<id; }; int main() Person p2(10),p1(20),p3(30); p1.showID(); p2.showID(); p3.showID();
Output
My ID is 20
My ID is 10
My ID is 30

5. Overloaded Constructors
There may be many constructors of a class, each having different number of arguments

6. Example Output Feet = 1.... Inches = 5 Feet = 5.... Inches = 9
#include<iostream> using namespace std; class Distance { private: int feet; float inches; public: Distance(): feet(1), inches(5.0) } Distance(int ft, float in): feet(ft), inches(in) void showDist() cout<<"\n Feet = "<<feet<<".... Inches = "<<inches; }; void main() Distance d1; Distance d2(5,9); d1.showDist(); d2.showDist();
Output
Feet = Inches = 5
Feet = Inches = 9

7. Default Copy Constructor
A no-argument constructor initializes data members with constant values
A multi-argument constructor initializes data members to values passed as arguments
We can also initialize an object with another object of same class
Surprisingly, we don’t need to write a special constructor for it
It is already built into all classes and known as “default copy constructor”

8. Example Output dist1 = 11'-6.25" dist2 = 11'-6.25" dist3 = 11'-6.25”
#include <iostream> using namespace std; class Distance { private: int feet; float inches; public: Distance() : feet(0), inches(0.0) { } Distance(int ft, float in): feet(ft), inches(in) void showdist() { cout << feet << "\'-" << inches << "\""; } }; int main() Distance dist1(11, 6.25); //two-arg constructor Distance dist2(dist1); //one-arg constructor Distance dist3 = dist1; //default copy constructor cout << "\ndist1 = "; dist1.showdist(); cout << "\ndist2 = "; dist2.showdist(); cout << "\ndist3 = "; dist3.showdist(); cout << endl; return 0; }
Output
dist1 = 11'-6.25"
dist2 = 11'-6.25"
dist3 = 11'-6.25”

9. Multiple Classes
In real world scenarios, we may have deal with different classes in a single problem
In an OO program, we may define as many classes as we need to represent a real world problem

10. Example
OOP
#include <iostream> #include<stdio.h> #include<cstring> using namespace std; class Car { public: int number; char color[10]; Car() { } Car(int n, char col[10]): number(n) { strcpy(color,col); } }; class Person private: int id; char name[10]; Car myCar; Person(): id(0)
void setData(int i, char n[10], Car c) {
id=i;
strcpy(name,n);
myCar=c; }
void showData()
cout<<"\n I am ID No. "<<id<<", my name is "<<name<<". I have car number "<<myCar.number<<" of color "<<myCar.color; };
int main()
Person p1, p2, p3;
Car c1(3439, "Red"),c2(7777, "Black");
p1.setData(1,“Tahira",c1);
p2.setData(2,“Maryam",c2);
p3.setData(3,“Kainat",c1);
p1.showData();
p2.showData();
p3.showData();
cout<<"\n";
return 0;
Malik Jahan Khan

11. Output
I am ID No. 1, my name is Tahira. I have car number 3439 of color Red
I am ID No. 2, my name is Maryam. I have car number 7777 of color Black
I am ID No. 3, my name is Kainat. I have car number 3439 of color Red