Inheritance

Prepared by : SELVIN JOSY BAI. S

 Itis the capability of one
class to inherit properties
from another class.
 The technique of building
new classes from the
existing classes is called
inheritance.

Base Class /
Super Class

Derived from

Derived Class /
Sub Class

 It is the class whose
properties are inherited by
another class.
 It is also called Super
Class.

 It is the class that inherit
properties from base class(es).
 It is also called Sub Class.
 It inherits all the properties of
the base class and can add
additional features to the
derived class.

 CODE REUSABILITY

 EASY
TO IMPLEMENT REAL
WORLD MODELS

 TRANSITIVE NATURE

 It is any of the access labels:
private, public or protected.
 It defines the accessibility of the
members of the base class within
the derived class.
 If the visibility mode is not
specified, it will be taken as
private by default.

 Privatemembers can never be
inherited. Only the public and
protected members can be
inherited to the derived class. This
is the difference between the
private and protected members.

VISIBILITY MODES
Derived class visibility

Base Class
Visibility Public Private Protected
derivation derivation derivation

Private Not Not Not
inherited inherited inherited

Protected Protected Private Protected

Public Public Private Protected

Access Accessible Accessible Accessible
Specifier of from own from derived from objects
members class class outside class

PRIVATE YES NO NO

PUBLIC YES YES YES

PROTECTED YES YES NO

 Private members of the base class cannot
be inherited with any of the visibility
mode.
 One is by making the visibility mode of
private members as public, but they will
be exposed to the outside world.
 Another is to convert the private members
into protected so that they will be hidden
from the outside world but can be
inherited.

Friendship Derivation
Provide access to private and Private members cannot be
protected members. derived into another class.

A non-member function can It shares the features of base
make friendship to a class class and adds some more
attributes
Two independent classes can The derived classes are created
have friendship, where friend with the help of base class.
function acts as bridge Derived class is a special
between them. instance of base class.
Friendship is not Derivation Derivation is a kind of
Friendship.

1. SINGLE INHERITANCE
2. MULTIPLE INHERITANCE
3. HIERARCHICAL INHERITANCE
4. MULTILEVEL INHERITANCE
5. HYBRID INHERITANCE

 Derivation of a class from only
one base class is called SINGLE
Inheritance.
 In the figure class Y is derived
from class X.

X BASE CLASS

Y DERIVED CLASS

class DerivedClassName : [visibility mode]
BaseClassName
{
//DataMembers and MemberFunctions;
}

Example:
class Automobile : public Vehicle
{
}

 Derivation of a class from SEVERAL
(TWO OR MORE) base classes is
called MULTIPLE Inheritance.
 In the figure class Z is derived from
both the classes X & Y.

X Y BASE CLASSES

Z DERIVED CLASS

class DerivedClassName : [visibility mode]
BaseClassName1, [visibility mode] BaseClassName1
{
}

Example:
class CHILD : public FATHER, public MOTHER
{
}

 Derivation of SEVERAL classes from
SINGLE base class is called
HIERARCHICAL Inheritance.
 In the figure the classes Y & Z is
derived from the same class X.

X BASE CLASSES

Y Z DERIVED CLASS

class DerivedClassName1 : [visibility mode] BaseClassName
{
----------;
}

{
----------;
}

Example: Example:
class Y : public X class Z : public X
{ {
---------; ---------;
} }

 When a sub class is
derived from a base X
class which itself is
derived from another
class, it is known as
MULTILEVEL Inheritance. Y
 In the figure the class Z is
derived from class Y,
which is a derived class
that is inherited from the Z
class X.

{
----------;
}

class DerivedClassName2 : [visibility mode] DerivedClassName1
{
----------;
}

Example: Example:
class Y : public X class Z : public Y
{ {
---------; ---------;
} }

 Derivation of a class
involving more than W
one form of Inheritance
is known as HYBRID
inheritance. X Y
 As it is the derivation of
a class from other
derived classes, which Z
are derived from the
same base class.

 The derived class need have a
constructor as long as the base
class has a no-argument
constructor.
 If the base class has constructors
with arguments, then it is mandatory
for the derived class to have a
constructor and pass the arguments
to the base class constructor.

 When an object of a derived class is
created, the constructor of the base
class is executed first and later the
constructor of the derived class.
 Unlike constructors, destructors in
the class hierarchy are invoked in
the reverse order of the constructor
invocation.

 It is one that has no instances and is
not designed to create objects.
 It is only designed to be inherited
from.
 It specifies an interface at a certain
level of inheritance and provides a
framework or skeleton, upon which
other classes can be built.

 When classes are derived in the
form of hybrid inheritance, there can
be a problem by which multiple
copies of the base class members
come in the lowest level derived
class through the various
intermediate subclasses. Here
comes the virtual base class for
rescue.

class A
{ public:
int a;
};
Class B
class B : public A
{ public: contains
int b; a and b
};

class C : public A
Class C
{ public: contains
int c; a and c
};

class D : public B, public C Class D
{ public: contains a,b,
int d;
};
a,c, & d

class A
{ public: only one copy of A will be inherited
int a;
};
Class B
class B : virtual public A
{ public: contains
int b; a and b
};

class C : virtual public A
Class C
{ public: contains
int c; a and c
};

class D : public B, public C Class D
{ public: contains a,b,
int d;
};
c, & d

 In inheritance, if the class D is derived
from the class B, it is said that D is a kind
of B; the class D has all the properties of
B in addition to the features of its own.
 In OOP, the containership occurs when
an object of one class is contained in
another class as a data member.
 In other words, a class can contain
objects of other classes as its members.

class ABC
{
int a;
float b;
public:
void fab();
};
class PQR
{
int p;
float q;
public:
ABC ob1;
void fab();
};

Inheritance

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Editor's Notes