1.
Function Overloading
and Overriding

2.
Overloading Introduction
One of the more powerful features for code readability and
usability is that of overloading.
Like most things, it can be used for both good andevil.
Function overloading is the availability of various functions within
a class that differ from each other in function signature i.e.
various functions share same name with different parameter
types or number of parameters.

3.
Functions in C++
A function in C++ is not uniquely identified by its name
alone.
Each function has a function signature, consisting of two
elements.
The name of the method
The order and type of its parameters.
Together, these act as the unique identifier for a C++
method.
The following thus are two different functions:
addTwo (int x, int y);
addTwo (float x, float y);

4.
Function Overloading
The process of providing more than one functions with
the same name is called method overloading.
We say that these functions have been overloaded.
Overloading makes sure that we can provide a consistent
and clear interface to our methods regardless of the
parameters type.
We don’t need addTwoInts and addTwoFloats, for example.

5.
Function Overloading
The compiler works out which of the methods to call
based on the parameters it is passed.
It will check for the method that has a matching signature.
It will execute that method only.
If no matching signatures are found, a compile-time error
will be displayed.

6.
Function Overloading
int add_nums (int one, int two) {
return one + two;
}
int add_nums (float one, float two) {
return (ceil (one + two));
}
int main() {
int answer_one, answer_two, answer_three;
answer_one = add_nums (1, 2); // Fine
answer_two = add_nums (1.0f, 2.0f); // Fine
answer_three = add_nums (1.0f, 2) // Error
}

7.
Function Overriding
A function in child class overrides a function in parent
class if they have the same name and type signature.
Classes in which functions are defined must be in a
parent-child relationship.
Overloading deals with multiple functions in the same
class with the same name but different signatures
Overriding deals with two functions, one in a parent class
and one in a child class, that have the same signature

8.
Function Overriding
class Base
{
protected:
void myFunc() { cout<<"Base Class’ Function"; }
};
class Derived: public Base {
public:
void myFunc() { cout<<"Derived Class’ Function"; }
void myFunc(int a)
{
cout<<"Derived Class’ Function with Parameter
Value“<<a;
}
};

9.
Function Overriding

10.
Function Overriding
To access the overridden function of base class from
derived class, scope resolution operator ::.
Following statement is used in derived class to access
the base class get_data() function:
A::get_data; // Calling get_data() of class A.

11.
Code
classA
{
public:
void fun()
cout << "n-> BASE <-n"; }{
};
class B:publicA {
public:
void fun()
{
A::fun();
cout << "-> DERIVED <-nn";
}
};
void main()
{
B b1;
b1.fun();
}

12.
Output

13.
Code
classA
{
public:
void fun()
cout << "n-> BASE <-n"; }{
};
class B:publicA {
public:
void fun()
{
cout << "-> DERIVED <-nn";
}
};
void main()
{
A *a1;
B b1;
a1=&b1;
a1->fun();
}

14.
Virtual function
classA
{
public:
virtual void fun()
cout << "n-> BASE <-n"; }{
};
class B:publicA {
public:
void fun()
{
cout << "-> DERIVED <-nn";
}
};
void main()
{
A *a1;
B b1;
a1=&b1;
a1->fun();
}

15.
Output