- One of the powerful features in object oriented programming
in inheritance
- When we define a class that is closely related to an
existing class, we can use this
existing class to define the new class
- Syntax:
class myOldClass { variables + functions ... } class myNewClass public : public myOldClass { more variables + more functions ... } - Example:
class myOldClass { public: int i1; void func1(int i) { i1 = i1 + i; } };class myNewClass : public myOldClass { public: int i2; void func2(int i) { i2 = i2 - i; } };It is as though we have defined myNewClass as follows:
class myNewClass { public: int i1; int i2; void func1(int i) { i1 = i1 + i; } void func2(int i) { i2 = i2 - i; } }; - Example Program:
(Demo inheritance) ---
click here
- The existing class
myOldClass is called
the parent class
- The new class defined using myNewClass is called the child class and myOldClass is the parent class of myNewClass
- Clearly, the obvious use of the inheritance mechanism is
program re-use:
the inheritance mechanism allows programmers to include
existing programs as base to write new programs.
The way to do that should be obvious; and I will not spend much time dwelling on examples.
- Another practical usage of the inheritance mechanism that is
less obvious is it indirectly provides
the programmer with the ability to write the type of
programs that I have eluded in the previous webpage.
Before we can understand how such program can be written, I need to discuss function polymorphism first.