| |||
What is Inheritance / how is it implemented in C++ (1)
OO in C++ - beyond the basics example from a Well House Consultants training course
More on OO in C++ - beyond the basics [link]
Source code: first_inheritance.cpp Module: C233
using namespace std;
/* This is a complete example! - A base class "Animal" - subclass "Human" - subclass "Pet" We set up an array of four Animals in a test program (2 humans and 2 pets) and then we loop thought them, reporting the age (which is implemented ONCE in the base class because it's common code) and the name (which is implemented in each subclass, because it differs between humans and pets) Compile and load line: g++ -o first_i first_inheritance.cpp Take a deep breath. It's unusual to do this in one file. It would normally be in ... 7 3 files of headers, one for each class 3 files of source, one for each class and the test program (a.k.a. the application) You would compile each of the four sources separately, pulling in the correct headers via #includes, and you would use #ifndefs to avoid duplicate loading. That will be our next example. */ #include <iostream> // Define the API to the classes // ----------------------------- // Common things in "animal" /* Note the "virtual" declaration which says that every animal has a name, but it will be handled differently depending on the type of animal. (The {} pair is VITAL!) */ class Animal { public: Animal(int age); int getAge(); virtual char *getName() {}; protected: int age; }; // Specifics in "human" and "pet" class Human : public Animal { public: Human(char *forename, char *surname, int age); char *getName(); protected: char *forename; char *surname; }; class Pet : public Animal { public: Pet(char *name, int age, char *breed, int weight); char *getName(); protected: char *name; }; // Define the classes themselves // ----------------------------- Animal::Animal(int age) { this->age = age; } int Animal::getAge() { return this->age; } // Note that the Human constructor calls the Animal constructor ... Human::Human(char *forename, char *surname, int age) : Animal (age){ this->forename = forename; this->surname = surname; } Pet::Pet(char *name, int age, char *breed, int weight): Animal (age) { this->name = name; } char *Human::getName() { // Should really concat strings but this is an inheritance // demo and not a string one! return "Mrs Smith"; } char *Pet::getName() { return this->name; } // Main test program // ----------------- int main () { // Set up object pointer array for the underlying base class Animal * Ourhouse [4]; int k; // Set up objects that are animals within that array // even if they are specialised types of animal Ourhouse[0] = new Human("Lisa","Ellis",21); Ourhouse[1] = new Human("Graham","Ellis",55); Ourhouse[2] = new Pet("Gypsy",4,"Dog",30); Ourhouse[3] = new Pet("Charlie",13,"Cat",3); // Loop through the animals and get their names, even // through that will be done differenly for pets and humans for (k=0; k<4; k++) { char * Name = Ourhouse[k]->getName(); int years = Ourhouse[k]->getAge(); cout << "Living there ... " << Name << " aged " << years << endl; } return 0; } /* Sample Output wizard:cpp graham$ ./first_i Living there ... Mrs Smith aged 21 Living there ... Mrs Smith aged 55 Living there ... Gypsy aged 4 Living there ... Charlie aged 13 wizard:cpp graham$ */ Learn about this subject
This module and example are covered on the following public courses:
* Learning to program in C and C++ * C++ for C Programmers * C and C++ Programming * Learning to program in C and C++ * C and C++ Programming Also available on on site courses for larger groups Books covering this topic
Yes. We have over 700 books in our library. Books
covering C and C++ are listed here and when you've selected a
relevant book we'll link you on to Amazon to order.
Other Examples
This example comes from our "OO in C++ - beyond the basics" training module. You'll find a description of the topic and some
other closely related examples on the "OO in C++ - beyond the basics" module index page.
Full description of the source code
You can learn more about this example on the training courses listed on this page,
on which you'll be given a full set of training notes.
Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License. Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre. • The Horse's mouth provides a daily tip or thought. • Further resources are available via the resources centre. • All of these resources can be searched through through our search engine • And there's a global index here. Web site author
Purpose of this website
This is a sample program, class demonstration or answer from a
training course. It's main purpose
is to provide an after-course service to customers who have attended our
public private or
on site courses, but the examples are made
generally available under conditions described below.
Conditions of use
Past attendees on our training courses are welcome to use individual
examples in the course of their programming, but must check
the examples they use to ensure that they are suitable for their
job. Remember that some of our examples show you how not to do
things - check in your notes. Well House Consultants take no responsibility
for the suitability of these example programs to customer's needs.
This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details. Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request. | |||
PH: 01144 1225 708225 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho PAGE: http://www.wellho.net/resources/ex.php • PAGE BUILT: Sun Oct 11 14:50:09 2020 • BUILD SYSTEM: JelliaJamb |