Inheritance is a way to reuse code of existing objects, or to establish a subtype from an existing object, or both, depending upon programming language support.

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How to replace inheritance with composition in this case?

I've recently read several articles about the advantages of the composition over inheritance. Their authors said that you can always replace inheritance with composition (to be precise, they say they ...
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3answers
179 views

UML Class Diagram: How can I represent “orthogonal” generalizations (or multi-inheritence)?

I try to represent in a UML Class Diagram the following object and features: The Object: A System (e.g. an electronic device) that can be of Type A, B or C If the System is of type A, it has a ...
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1answer
44 views

Representing the hierarchy of groups of numbers using type inheritance

I've run into an interesting conundrum while coding my own implementations for the basic sets of mathematical numbers (Natural, Integer, Rational, Irrational, Real, Complex). I'm doing this mostly for ...
2
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1answer
96 views

Is this approach to CSS correct?

Reading SASS basic features on their website, I stumbled upon the @extend feature. The example they give is the following: .message { border: 1px solid #ccc; padding: 10px; color: #333; ...
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0answers
256 views

JavaScript Combination Inheritance Pattern

In the chapter of Professional JavaScript for Web Developers on OOP, Nicholas Zachas describes a JavaScript inheritance pattern which he refers to as combination inheritance. The basic idea is that ...
25
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1answer
1k views

How are mixins or traits better than plain multiple inheritance?

C++ has plain multiple inheritance, many language designs forbid it as dangerous. But some languages like Ruby and PHP use strange syntax to do the same thing and call it mixins or traits. I heard ...
2
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2answers
142 views

Wrapping constructor arguments

Given a base class with around 25 or so subclasses, I have found that adding an argument to the base constructor is painful. protected AbstractController(Service1 s1, Service2 s2, Service3 s3){ ... } ...
2
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4answers
188 views

Subclass only have methods without variables

Is it ok to have subclass which does not declare its own variables (instance variables) and inherits from super class or base class? It has methods and there are some common methods which it overides ...
2
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5answers
413 views

Classic inheritance problem?

I keep seeing the following pattern when people learn about OOP: Problem: How do I put objects of different but related types into a container? Solution: Inherit from a common base class. New ...
2
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2answers
83 views

subclass reference to another subclass

Imagine I have the following code: class A: pass class B(A): pass class C(A): def __init__(self): self.b = B() Is the above code correct in terms of correct inheritance? I ...
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2answers
1k views

A vector of pointers to different derived classes of the same base class

I am writing a game in C++ which has different enemy types. I have defined a base Enemy class and I also have derived classes enemy1, enemy2 etc. Now for updating these enemies in each iteration of ...
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1answer
86 views

Adding new functionality to all of shelve.Shelf's subclasses in Python

In order to avoid the overhead associated with the shelve module's writeback option I'm interested in putting together a shelf class that only accepts hashable values, with hashability being a proxy ...
0
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1answer
216 views

Doctrine 2 and Concrete table inheritance

I use Doctrine 2 and I've read some articles on inheritance strategies' mapping with ORM. I've seen three main strategies : "Class table inheritance", "Concrete table inheritance" and "Single table ...
3
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1answer
121 views

Why is subclassing TraversableOnce not recommended

Reading http://www.scala-lang.org/api/2.11.1/index.html#scala.collection.TraversableOnce: Directly subclassing TraversableOnce is not recommended - instead, consider declaring an Iterator with a ...
4
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2answers
1k views

Code re-use in C++, via multiple inheritance or composition? Or…?

I originally asked this question on StackOverflow, but I was directed here, and I think my problem is perhaps as much conceptual as technical, so here goes. If you’re defining a hierarchy of abstract ...
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1answer
75 views

Public versus private inheritance when some of the parent's methods need to be exposed?

Public inheritance means that all fields from the base class retain their declared visibility, while private means that they are forced to 'private' within the derived class's scope. What should be ...
0
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1answer
71 views

Matching the superclass's constructor's parameter list, is treating a null default value as a non-null value within a constructor a violation of LSP? [duplicate]

I kind of ran into this when messing around with FlashPunk, and I'm going to use it as an example. Essentially the main sprite class is pretty much class Entity. Entity's constructor has four ...
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3answers
225 views

What alternative is better to diagram this scenario?

I was creating and discussing a class diagram with a partner of mine. To simplify things, I've modify the real domain we're working on and made up the following diagram: Basically, a company works ...
3
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1answer
402 views

How to maintain encapsulation with composition in C++?

I am designing a class Master that is composed from multiple other classes, A, Base, C and D. These four classes have absolutely no use outside of Master and are meant to split up its functionality ...
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0answers
66 views

Example of persisting an inheritance relationship using ORM

I have some experience with OOP and RDBs, but very little exposure to web programming. I am trying to understand what non-trivial types of problems are solved by ORM. Of course, I am familiar with the ...
5
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3answers
268 views

How to refactor my design, if it seems to require multiple inheritance?

Recently I made a question about Java classes implementing methods from two sources (kinda like multiple inheritance). However, it was pointed out that this sort of need may be a sign of a design ...
0
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2answers
406 views

Can an object call a method on it's immediate descendant? [closed]

I have an inheritance hierarchy three deep : an abstract base class, from which I derive another abstract class, call it the intermediate class, from which will derive possibly a large variety of ...
0
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1answer
181 views

overriding implemented base class methods

I read somewhere that the chain of inheritance breaks when you alter a behavior from derived class. What does "altering a behavior" mean here? Is overriding an already implemented method in base class ...
3
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4answers
628 views

Why is there no 'subclasses-only' access modifier in Java?

In Java, there are four available access modifiers for methods: public - any class can use this method. protected - classes in the same package and subclasses in any package can use this method. ...
7
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4answers
311 views

Is inheritance that adds rules bad? [duplicate]

I got into a debate on this question which distilled to if it is a good idea for a specialization of a class to add business rules. Unfortunately this point got trampled in the comments so I'm asking ...
76
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12answers
8k views

Why would Square inheriting from Rectangle be problematic if we override the SetWidth and SetHeight methods?

If a Square is a type of Rectangle, than why can't a Square inherit from a Rectangle? Or why is it a bad design? I have heard people say: If you made Square derive from Rectangle, then a Square ...
2
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0answers
216 views

Reusable and customizable charting library on top of d3js

I have started building a charting library on top of d3js using javascript's inheritance. My goal is to develop reusable and fully customizable chart components. I read the article: Towards Reusable ...
2
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3answers
257 views

Is it appropriate to use inheritance to prevent code duplication of the logic for a user control?

Suppose I have two or more UserControl implementations with vastly different implementations but near identical code-behind. One strategy to avoid code duplication is as follows: Change each ...
2
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3answers
388 views

Inheritance: Is code from superclass virtually *copied* to subclass, or is it *referred-to by subclass*?

Class Sub is a subclass of class Sup. What does that mean practically? Or in other words, what is the practical meaning of "inheritance"? Option 1: The code from Sup is virtually copied to Sub. (as ...
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1answer
223 views

Should I use inheritance or an interface?

So in a nutshell I have an abstract class : public abstract class Member { public string PCode { get; set; } public string Reference { get; set; } public DateTime? ElectedDate { get; set; } } And ...
4
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2answers
1k views

What is the process of determining which method in a class hierarchy should execute known as?

I thought I understood inheritance and polymorphism, but I was given this question, and I can't, for the life of me, figure out what the proper answer is or what they're trying to get at: The ...
2
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2answers
388 views

Testing abstract class' behavior

I'm currently refactoring an existing design, which was created without TDD. There is a class hierarchy with one abstract base class and two subclasses. In the original design, these classes were ...
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2answers
112 views

Inheritance vs 'specification' by fields

I'm currently reading 'Head first design patterns', and already the first chapter threw some questions towards me. This chapter introduces the 'prefer composition over inheritance' design principle, ...
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1answer
125 views

When is it suitable to use inheritance [duplicate]

I recently had a small "argument" about inheritance with a friend. I think people overuse it a lot. Intuition tells me that that the only good reason for class inheritance is polymorphism - when there ...
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2answers
145 views

Alternatives to inheritance on complex structures?

I'm working on an ASP.NET Webforms project, using the MVP Pattern (which the presenters as you may know use a Page Controller pattern). I'm given a rather complex inheritance chain for my controllers. ...
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3answers
318 views

Why are inheritance and interfaces restricted to instance members?

Disclaimer: I think the rules are almost the same in most OO languages, but since I'm most familiar with C# I'll be relating to this specific language. I think that the use of attributes and ...
3
votes
3answers
507 views

Why should one subclass instead of composite when using the Factory Method design pattern?

I'm currently learning about design patterns. I learned about the Factory Method pattern. This pattern means that in order to implement a factory to create objects, one should subclass the class that ...
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3answers
647 views

Should utility base classes be avoided

Knowing that C# doesn't support multiple inheritance, is it considered bad form to write a utility base class? Some initial thoughts: I could create an interface and a concretion, but then the ...
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5answers
227 views

Clarification about Polymorphism / Inheritance

I am trying to better my understanding of polymorphism. Say I have a base class called baseClass with one method called foo() and I have three derived classes called derived1 , derived2 and derived3 ...
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1answer
86 views

Concerning JavaScript prototype and the initial constructor function

I am going through a tutorial on OOP in JavaScript (javascriptissexy.com using OOP in JS: What you Need to know). The instructor is explaining the Constructor/Prototype pattern of object creation. I ...
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1answer
484 views

inheritance and static final variables

I'm a programing student. I've been having problem to organize Java classes that use inheritance and static final variables. Let say I have an abstract class named Form that has two children named ...
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1answer
524 views

Changing method signature for implementing classes in PHP

Is there any decent work around to PHP's lack of Generics that allow static code inspection to detect type consistency? I have an abstract class, that I want to sub-class and also enforce that one of ...
0
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1answer
59 views

Would it make sense to add parameters of an inferred type to inheritance?

I'll write this in PHP (where this thought originated), but this is generic to any object-orientated language. Basically, this is an addition to abstract classes that defines the implementation of its ...
0
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1answer
207 views

Can we say that Java or C# have unified inheritance trees?

Can we say that Java or C# are OO languages with a unified inheritance tree/unified type system? By unified inheritance tree/unified type system I mean that every class derives implicitly or ...
2
votes
3answers
967 views

Why is inheritance only defined at compile-time?

I found this statement from the gang of four's "Design Patterns" particularly odd; for some context, the authors are comparing inheritance versus composition as reuse mechanisms [p. 19]: "...you ...
2
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3answers
143 views

Refactor an old model of a LastUser Modification on every Object?

I have a software requirement, that needs to store the user that made the last modification to another object, for every object (assume that all objects are already mapped and into a BD). So we have ...
2
votes
1answer
157 views

Using partially implemented interfaces

Consider the following hierarchy in C++ notation: class A { public: virtual void doStuff()=0; virtual void doOtherStuff()=0; }; class B:public A { public: ...
0
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2answers
264 views

block access to area/controller's methods but allow inherited controller to run methods, asp .net mvc5

I am trying to find out how to block a whole area/controller from being accessed by typing url website.com/area1/basecontroller/method1 (this area also contains the views that will be displayed) , ...
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2answers
399 views

Help with inheritance hierarchy design

I'm having trouble designing an inheritance hierarchy. In the figure: Base class: This uses the Template Method. Contains core logic/algorithm that calls virtual/abstract methods Derived ...
4
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1answer
387 views

Inheritance in test classes

I have an interface Serializer with methods serialize and isSerializerFor. I created a first implementation of this using TDD, and ended up with a nice clean test case fully covering a nice clean ...