Computer Science
Inheritance in Oops
In object-oriented programming, inheritance allows a new class to inherit properties and behaviors from an existing class. This promotes code reusability and allows for the creation of a hierarchy of classes. The derived class (or subclass) inherits the attributes and methods of the base class (or superclass), and can also have its own unique attributes and methods.
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No longer available |Learn moreProgramming Fundamentals Using JAVA
A Game Application Approach
- William McAllister, S. Jane Fritz(Authors)
- 2021(Publication Date)
- Mercury Learning and Information(Publisher)
parent class.The concept of inheritance is fundamental to object oriented programming. If properly used, it can greatly reduce the time and effort required to develop a software product. For example, suppose that one of the classes specified during the design of a new program is similar to an existing class in that the existing class contains many of the data members and methods listed in the new class’s UML diagram. The best way to develop the new class would be to simply add the existing class to the program and modify and/or add to it. One approach to this would be to copy the source code of the existing class, paste the code into a new class, and then modify the copied code. A better approach would be to use the concept of inheritance.Although we may have been importing the existing class into our programs for many years, we may not have its source code. For example, the Java API does not contain the source code of any of the classes included in it. Rather, it contains the classes’ translated byte codes. This fact would eliminate the copy and paste alternative but not the inheritance alternative. To use the concept of inheritance, we only need the byte codes of the existing class. In addition, software engineering studies reveal that copying, pasting, and modifying code that we did not write can be more time consuming than a completely independent development of a new class. Inheritance allows us to modify an existing class that was added to a new program in a way that does not introduce the errors that are associated with the copy-paste-modify alternative.
No longer available |Learn more- Richard Grimes(Author)
- 2017(Publication Date)
- Packt Publishing(Publisher)
In basic terms, inheritance is when one class extends another class the class being extended is called the base class, parent class, or superclass, and the class doing the extending is called a derived class, child class, or subclass. However, there is an important concept to understand with inheritance: the relationship of the derived class to the base class. It is commonly given in terms of is-a. If the derived class is a type of base class, then the relationship is inheritance. An mp3 file is an operating system file, so if you have a os_file class, then you could legitimately derive from it to create an mp3_file class. The derived class has the functionality and state of the base class (although it may not have complete access to them, as will be explained later), so it can use the functionality of the base class. In this case, it is similar to composition. However, there are significant differences. In general, in composition, the composed object is used by the class and not exposed directly to the client of the class. With inheritance, an object of the derived class is an object of the base class, so usually the client code will see the base class functionality. However, a derived class can hide the functionality of the base class, so client code will not see the hidden base class member, and the derived class can override the base class methods and provide its own version. There is a lot of disagreement in the C++ community over whether you should use inheritance or composition to reuse code, and there are advantages and disadvantages of each. Neither is perfect and often a compromise is needed. Inheriting from a class Consider a class that wraps an operating system. This will provide lots of methods to give access to things such as the creation date, modification date, and the size of the file obtained by calling operating system functions. It could also provide methods to open the file, close the file, map the file into memory, and other useful things
eBook - PDF- Harold Cabrera(Author)
- 2002(Publication Date)
- Syngress(Publisher)
Object-Oriented Programming Solutions in this chapter: 218 Chapter 6 • Object-Oriented Programming Introduction In the last chapter, you learned about C# objects and classes. As you know, there is more to object-oriented programming (OOP) than just classes and objects. This chapter will explain most of the remaining OOP concepts that you will need to know.You will learn about inheritance, polymorphism, inner classes, and interfaces. The chapter will begin by discussing the C# inheritance model. Inheritance is the technique of deriving new classes from existing classes. Next, you will be introduced to the concept of polymorphism, which allows for method over-riding. In that section, you will learn about virtual methods and versioning with the new and override keywords, which is a feature of C# that is not found in Java. The next part of the chapter will describe C#’s support for inner classes.The chapter will wrap up by discussing interfaces. Interfaces are a way for dealing with the common situation of wanting an object to derive behavior from two different parents, sometimes referred to as multiple inheritance. Inheritance C#’s inheritance model is very similar to Java, with syntax being the only major difference.To start off, let’s review the theory behind this concept. Inheritance is a relationship between classes. In this relationship, a child class inherits the members and methods of a parent class. Inheritance is an important part of both the C# and Java object models. In both Java and C# all classes are derived from a common base class. Java classes all subclass java.lang.Object , and C# classes all subclass Object . In object-oriented programming, inheritance is a strong and fundamental rela-tionship. For example, I have a son who plays in a high school marching band.
eBook - PDF- Joyce Farrell(Author)
- 2018(Publication Date)
- Cengage Learning EMEA(Publisher)
Every individual plant and pet has slightly different characteristics, but within a species, you can count on many consistent inherited attributes and behaviors. Similarly, the classes you create in object-oriented programming languages can inherit data and methods from existing classes. In Java and all object-oriented languages, inheritance is a mechanism that enables one class to acquire all the behaviors and attributes of another class, meaning that you can create a new class simply by indicating the ways in which it differs from a class that already has been developed and tested. When you create a class by making it inherit from another class, the new class automatically contains the data fields and methods of the original class. Diagramming Inheritance Using the UML Beginning with the first chapter of this book, you have been creating classes and instantiating them. Programmers and analysts sometimes use a graphical language to describe classes and object-oriented processes; this Unified Modeling Language (UML) consists of many types of diagrams, some of which can help illustrate inheritance. For example, consider the simple Employee class shown in Figure 10-1. The class contains two data fields, id and salary, and four methods: a get and set method for each field. Figure 10-2 shows a UML class diagram for the Employee class. A class diagram is a visual tool that provides you with an overview of a class. It consists of a rectangle divided into three sections—the top section contains the name of the class, the middle section contains the names and data types of the attributes, and the bottom section contains the methods. Only the method return type, name, and arguments are provided in the diagram—the instructions that make up the method body are omitted. Copyright 2019 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part.
eBook - PDFMicrosoft® Visual C# 2015
An Introduction to Object-Oriented Programming
- Joyce Farrell, , , (Authors)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
Every plant and pet has slightly different characteristics, but within a species, you can count on many consistent inherited attributes and behaviors. In other words, you can reuse the knowledge you gain about general categories and apply it to more specific categories. Similarly, the classes you create in object-oriented programming languages can inherit data and methods from existing classes. When you create a class by making it inherit from another class, you are provided with data fields and methods automatically; you can reuse fields and methods that are already written and tested. You already know how to create classes and how to instantiate objects from those classes. For example, consider the Employee class in Figure 10-1. The class contains two data fields, idNum and salary , as well as properties that contain accessors for each field and a method that creates an Employee greeting. Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 425 Understanding Inheritance class Employee { private int idNum; private double salary; public int IdNum { get { return idNum; } set { idNum = value ; } } public double Salary { get { return salary; } set { salary = value ; } } public string GetGreeting() { string greeting = Hello.
eBook - PDF- Michael T. Goodrich, Roberto Tamassia, Michael H. Goldwasser(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
For each pattern, be it for algorithm engineering or software engineering, we explain its general use and we illustrate it with at least one concrete example. 64 Chapter 2. Object-Oriented Design 2.2 Inheritance A natural way to organize various structural components of a software package is in a hierarchical fashion, with similar abstract definitions grouped together in a level-by-level manner that goes from specific to more general as one traverses up the hierarchy. An example of such a hierarchy is shown in Figure 2.3. Using mathematical notations, the set of houses is a subset of the set of buildings, but a superset of the set of ranches. The correspondence between levels is often referred to as an “is a” relationship, as a house is a building, and a ranch is a house. Building Low-rise Apartment High-rise Apartment Two-story House Ranch Skyscraper Commercial Building House Apartment Figure 2.3: An example of an “is a” hierarchy involving architectural buildings. A hierarchical design is useful in software development, as common function- ality can be grouped at the most general level, thereby promoting reuse of code, while differentiated behaviors can be viewed as extensions of the general case. In object-oriented programming, the mechanism for a modular and hierarchical orga- nization is a technique known as inheritance. This allows a new class to be defined based upon an existing class as the starting point. In object-oriented terminology, the existing class is typically described as the base class, parent class, or super- class, while the newly defined class is known as the subclass or child class. We say that the subclass extends the superclass. When inheritance is used, the subclass automatically inherits, as its starting point, all methods from the superclass (other than constructors). The subclass can differentiate itself from its superclass in two ways. It may augment the superclass by adding new fields and new methods.
eBook - ePubIT Interview Guide for Freshers
Crack your IT interview with confidence
- Sameer S Paradkar(Author)
- 2019(Publication Date)
- BPB Publications(Publisher)
Class: A class explains the attributes and functions that define the behavior. A class is a template for an object. A class is a complete data type, which represents a template for the objects. A class is the fundamental building block of the OOPs application. This is usually a template that defines the properties, behaviors, events for a particular group of objects. The class consists of behavior and data. For example, the aircraft class contains data such as category, model number, color, and behavior such as length of the flight time, speed, and total number of passengers. A class can inherit the behaviors and data from the other classes by extending these classes, which are known as base or parent classes.- Object: An object is an instance of a class and is a fundamental building block of the OO program. An object is usually an entity consisting of behavior and attributes. Attributes and behavior for an object are described in the class definition.
What is the relation between an object and a class?
A class acts as a blueprint or a template that defines the behaviors, states and properties and that are common to objects. Objects are instances of a class. For example, in a class, Person, Math Teacher and Footballer will be derived classes. One can create n number of objects for the class Person such as Math Teacher and Footballer . To create an object of a class, the new operator is utilized. When an object is usually instantiated, the application allocates memory for the entire data members that are present in that particular class.Explain the concepts of OOPs.
The following are the key concepts of OOP:- Polymorphism: This facilitates leveraging an entity in various forms.
- Abstraction: This is a method of publishing just the relevant and important data to the end-users without exposing unnecessary details to the outside world.
- Inheritance:
No longer available |Learn more- Andrea Chiarelli(Author)
- 2016(Publication Date)
- Packt Publishing(Publisher)
In OOP, inheritance enables new objects to acquire the properties of existing objects. This relationship between two objects is very common and can be found in many situations in real life. It usually refers to creating a specialized object starting from a more general one. Let's consider, for example, a person: he has some features such as name, surname, height, weight, and so on. This set of features describes a generic entity that represents a person. Using abstraction, we can select the features needed for our purpose and represent a person as an object:If we need a special person who is able to program computers, that is a programmer, we need to create an object that has all the properties of a generic person plus some new properties that characterize the programmer object. For instance, the new programmer object can have a property describing which programming language they know.Suppose we choose to create the new programmer object by duplicating the properties of the person object and adding to it the programming language knowledge as follows:This approach is in contrast with the Object-Oriented Programming goals. In particular, it does not reuse existing code, since we are duplicating the properties of the person object. A more appropriate approach should reuse the code created to define the person object. This is where the inheritance principle can help us. It allows us to share common features between objects, avoiding code duplication:We can implement inheritance in JavaScript in various ways. Consider, for example, the following constructor of person objects:Note
Inheritance is also called subclassing in languages that support classes. A class that inherits from another class is called a subclass , while the class from which it is derived is called a superclass . Apart from the naming, the inheritance concept is the same, although of course it does not seem suited to JavaScript.
- Joyce Farrell(Author)
- 2012(Publication Date)
- Cengage Learning EMEA(Publisher)
However, OOP adds several new concepts to programming and involves a different way of thinking. A considerable amount of new vocabulary is involved as well. Five important features of object-oriented languages are: l Classes l Objects l Polymorphism l Inheritance l Encapsulation Classes and Objects In object-oriented terminology, a class describes objects with common attributes. An object is one instance of a class. Object-oriented programmers sometimes say an object is one instantiation of a class; this word is just another form of instance . For example, your redChevroletAutomobileWithTheDent is an instance of the class that is made up of all automobiles, and your GoldenRetrieverDogNamedGinger is an instance of the class that is made up of all dogs. A class is like a blueprint from which many houses might be constructed, or like a recipe from which many meals can be prepared. One house and one meal are each an instance of their class; countless instances might be created eventually. For example, Figure 7-1 depicts a Dog class and two instances of it. 253 Principles of Object-Oriented Programming Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Since the beginning of this book, you have created application classes that could be used without creating instances. In this chapter, you will create additional types of classes that client programs will instantiate ; that is, instances of the classes will be created. Objects both in the real world and in object-oriented programming contain attributes and methods.
eBook - PDFC++ Programming
Program Design Including Data Structures
- D. Malik(Author)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
5. In a multiple inheritance, a derived class is derived from more than one base class. 6. The private members of a base class are private to the base class. The derived class cannot directly access them. 7. The public members of a base class can be inherited either as public or private by the derived class. 8. A derived class can redefine the member functions of a base class, but this redefinition applies only to the objects of the derived class. 9. A call to a base class’s constructor (with parameters) is specified in the head-ing of the definition of the derived class’s constructor. 10. If in the heading of the definition of a derived class’s constructor, no call to a constructor (with parameters) of a base class is specified, then during the derived class’s object declaration and initialization, the default constructor (if any) of the base class executes. 11. When initializing the object of a derived class, the constructor of the base class is executed first. 12. Review the inheritance rules given in this chapter. 13. In composition (aggregation), a member of a class is an object of another class. 14. In composition (aggregation), a call to the constructor of the member objects is specified in the heading of the definition of the class’s constructor. 15. The three basic principles of OOD are encapsulation, inheritance, and polymorphism. 16. An easy way to identify classes, objects, and operations is to describe the prob-lem in English and then identify all of the nouns and verbs. Choose your classes (objects) from the list of nouns and your operations from the list of verbs. EXERCISES The number in parentheses at the end of an exercise refers to the learning objective listed at the beginning of the chapter. 1. Mark the following statements as true or false. a. In single inheritance, a base class can create only one derived class. (1) Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300
eBook - PDF- Joyce Farrell(Author)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
As with constructors, if you do not explicitly create a destructor for a class, one is automatically provided. The most com-mon way to declare a destructor explicitly is to use an identifier that consists of a tilde (~) followed by the class name. You cannot provide parameters to a destructor; as a consequence, destructors cannot be overloaded. Like a constructor, a destructor has no return type. • A class can contain objects of another class as data fields. Creating whole-part relation-ships is known as composition or aggregation (has-a relationship). • When you create a class by making it inherit from another class, you are provided with prewritten and tested data fields and methods automatically. Using inheritance helps you save time, reduces the chance of errors and inconsistencies, and makes it easier for readers to understand your classes. A class that is used as a basis for inheritance is called a base class. A class that inherits from a base class is a derived class or extended class. The terms superclass and parent class are synonyms for base class . The terms subclass and child class are synonyms for derived class . • Some of the most useful classes packaged in language libraries are used to create graphical user interface (GUI) objects such as frames, buttons, labels, and text boxes. Programming languages that supply existing GUI classes often provide a visual develop-ment environment in which you can create programs by dragging components such as buttons and labels onto a screen and arranging them visually. • Exception-handling techniques are used to handle errors in object-oriented programs. When you try a block of code, you attempt to use it, and if an exception occurs, it is thrown. A catch block of the correct type can receive the thrown exception and handle it. Many OOP languages provide built-in Exception types, and you can create your own types by extending the Exception class.
eBook - PDF- Michael T. Goodrich, Roberto Tamassia, David M. Mount(Authors)
- 2011(Publication Date)
- Wiley(Publisher)
For each pattern, be it for algorithm engineering or software engineering, we explain its general use and we illustrate it with at least one concrete example. 2.2. Inheritance and Polymorphism 71 2.2 Inheritance and Polymorphism To take advantage of hierarchical relationships, which are common in software projects, the object-oriented design approach provides ways of reusing code. 2.2.1 Inheritance in C++ The object-oriented paradigm provides a modular and hierarchical organizing struc- ture for reusing code through a technique called inheritance. This technique allows the design of generic classes that can be specialized to more particular classes, with the specialized classes reusing the code from the generic class. For example, sup- pose that we are designing a set of classes to represent people at a university. We might have a generic class Person, which defines elements common to all people. We could then define specialized classes such as Student, Administrator, and In- structor, each of which provides specific information about a particular type of person. A generic class is also known as a base class, parent class, or superclass. It defines “generic” members that apply in a multitude of situations. Any class that specializes or extends a base class need not give new implementations for the general functions, for it inherits them. It should only define those functions that are specialized for this particular class. Such a class is called a derived class, child class, or subclass. Let us consider an example to illustrate these concepts. Suppose that we are writing a program to deal with people at a university. Below we show a partial implementation of a generic class for a person. We use “// ...” to indicate code that is irrelevant to the example and so has been omitted. class Person { // Person (base class) private: string name; // name string idNum; // university ID number public: // .
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
