Function overloading and overriding

Function Overloading and
Overriding
PRESENTED BY:
RAJAB ALI

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 and evil.
 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.
rajabalicr7@gmail.com

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);

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.

 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.

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
}

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

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;
}
};

Function Overriding

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.

Code
class A
{
public:
void fun()
{ cout << "n-> BASE <-n"; }
};
class B:public A {
public:
void fun()
{
A::fun();
cout << "-> DERIVED <-nn";
}
};
void main()
{
B b1;
b1.fun();
} rajabalicr7@gmail.com

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

Virtual function
class A
{
public:
virtual void fun()
{ cout << "n-> BASE <-n"; }
};
class B:public A {
public:
void fun()
{
}
};
void main()
{
A *a1;
B b1;
a1=&b1;
a1->fun();
} rajabalicr7@gmail.com

Function overloading and overriding

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