Inheritance

Object Oriented
Programming using C++
Inheritance

Inheritance
Inheritance is a phenomenon of acquiring
properties from predecessor.
In object oriented systems, it means
acquiring the properties of base class to the
derived class.
Hence the derived class gets specialized with
the properties of base class as well as its own
properties.
It involves the concept of code reusability.

Inheritance
Inheritance is the process by which new classes
called derived classes are created from existing
classes called base classes.
The derived classes have all the features of the
base class and the programmer can choose to
add new features specific to the newly created
derived class.
The idea of inheritance implements the is a
relationship. For example, mammal IS-A animal,
dog IS-A mammal hence dog IS-A animal as well
and so on.

Types of inheritance:
single level
multi level
Base Class A
Derived Class B
Class A
Intermediate
derived class B
Derived Class C

Multiple inheritance
Hierarchical inheritance.
Base class A Base class B
Derived Class
C
Class A
Derived class B
Derived
class C
Derived class
D

Hybrid inheritance
Class A
Intermediate
Derived class B
Intermediate
Derived class C
Derived class D
Class A
Class B
Class C
Class D

FEATURES /ADVANTAGES OF
INHERITANCE
Reusability of Code
Saves Time and Effort
Faster development, easier maintenance and
easy to extend
Capable of expressing the inheritance
relationship and its transitive nature which
ensures closeness with real world problems

Syntax for inheritance:
class Base-class-name
{
___ //
___ // definition of the class
};
class derived-class name : visibility-mode
base-class-name
{
….. //
….. // members of derived class
};

Visibility Mode
Here visibility mode can be public, private
or protected.
Private is the default mode. They are visible
to member functions within its class.
Protected visible to member functions of
its own class and derived class.
Public visible to all functions in the
program.

When a class is inherited in any
of these visibility modes, the
visibility of its members varies.

The visibility of inherited members is
as shown:

Single level
In this kind of inheritance, there is a single
base class and a single derived class.
Eg: class base
{
// class declaration
};
class derived : public base
{
//derive class declaration
};
Here, base class base is inherited into the derived class derived.

Multi level Inheritance
In this type of inheritance
there is more than one
levels of inheritance and
each derived class serves as
the base class for the other
derived class.
Eg. class base1
{
//base1 declaration
};
class base2: public base1
{
//base2 declaration
};
class derived : public base2
{
//derived class
declaration
};
Here, base1 is a base class that
is inherited into the derived
class base2, which in turn is
inherited into the derived
class derived.

Question to implement
A class A{
char name[] …….
int roll_no; ……
+void get();
+void show(); };
B class B: public A
float m1,m2,m3; {
+void take(); …..
+void put(); };
C
class C: public B
float percentage; {
+void cal_per(); …..
+void disp_result(); };

Multiple Inheritance –
In this kind of Inheritance, there are many base classes and
one derived class from these base classes.
Eg. Class base1{};
class base2{};
Class base 3{};
class derived : public base1, protected base2, public base3
{
};
Here, base1, base2 and base3 are base classes that are
inherited into the derived class derived.

Hierarchical Inheritance
In this type of Inheritance, there
is one base class and many
derived classes from this base
class
Eg. class base
{
};
class der1 : public base
{
};
class der2 : public base
{
};
Here, der1 and der2 are derived
classes that are derived from
the base class base.

Hybrid Inheritance
This is a combination of one or more
than one type of Inheritance, like a
combination of multiple and multilevel
inheritance.

Virtual Base Classes
In hybrid Inheritance, that is a combination of
multiple and hierarchical inheritance, there may
arise a case when the features of ancestor base
class are inherited via multiple paths in to the
ultimate derived class, resulting in deriving
duplicate set of members.
This duplication of inherited members can be
avoided in C++ by inheriting the ancestor base
class as virtual base class in to any derived class.

Hybrid inheritance
Class A
Intermediate
Derived class B1
Intermediate
Derived class B2
Derived class C
Class A
{
// (ancestor) class declaration
};
Class B1: virtual public A
{
//(intermediate derived) class
declaration
};
{
//(intermediate derived) class
declaration
};
Class C: public B1, public B2
{// only one copy of the
members of class A is inherited
};

Syntax:
Class A
{
// (ancestor) class declaration
};
{
//(intermediate derived) class declaration
};
{
//(intermediate derived) class declaration
};
Class C: public B1, public B2
{// only one copy of the members of class A is inherited
};

Constructors in derived class:
• Whenever we have parameterized
constructors in Base class, it becomes
necessary to define a parameterized
constructor in derived class so that on the
creation of objects of derived class, we can
pass the parameters to the base constructors
through the derived constructor.

The format for the derived class constructor in this case
is a bit different as shown below:
class derived: <visibility mode> <base class name>
{
int A, B; //declaration of data members of class Derived
Public:
derived( arg 1, arg 2, arg 3…. arg N): base 1( arg a,arg b,,…,arg
d), base 2( arg e, arg f,… arg k),…base N( arg l, arg m…,arg p)
{
A= arg 1;
B= arg 2;
}
};

Abstract Classes
• Is one that is used to create objects.
• An abstract class is designed only to act as a
base class(to be inherited by other classes).

Inheritance

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