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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Is it ever appropriate to use subtyping for a has-a relationship?

One of the basic precepts of object oriented programming is that subtyping represents the "is-a" relationship. That is, the child is always a specific form of the parent. A common example is that a ...
25
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3answers
4k views

If I implement an Interface, is it called an Inheritance?

If my class implements an interface then can I say that I'm following inheritance? I know that when a class extends another class then it's inheritance.
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1answer
62 views

Get or infer template type from inherited member

So I have an assignment from college where I have to apply multiple metaheuristics to different problems. I thought that I should make everything as modular and reusable as possible to reuse ...
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2answers
123 views

Expressing interface inheritance in natural language [duplicate]

In object-oriented programming, when you extend a class you establish an is-a relationship between a new subtype and its parent(s), i.e. B is an A (aka code inheritance). When you compose a class with ...
3
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5answers
185 views

What is the correct OOP relation between complex and real numbers?

On one hand class complex { double real; double imaginary; } it is composition on the other hand class complex : double { double imaginary; } it is inheritance Which one is ...
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3answers
2k views

Is there a specific name for the “Square inherits from Rectangle” paradox?

A certain failure of OOP is shown with a class Square inheriting from Rectangle, where logically Square is a specialization of Rectangle and should therefore inherit from it, but everything falls ...
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2answers
94 views

Do you say “this” on protected members? [closed]

Background I have never had a formal class in OOP/OOD although I understand how the protected members work. Being accessible by any instance/derived class, they are thereby less private (more ...
2
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1answer
137 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
92 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 ...
3
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2answers
193 views

How do I deal with unneeded inherited members?

Consider the following UML diagram: In a nutshell: ChildClass1 and ChildClass2 use all of the members of ParentClass. ChildClass3only uses Member1 and Member2 and the value of Member5 is a ...
4
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1answer
295 views

Liskov substitution principle with abstract parent class

Does Liskov substitution principle apply to inheritance hierarchies where the parent is an abstract class the same way if the parent is a concrete class? The Wikipedia page list several conditions ...
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5answers
1k views

Does this code solve the square/rectangle Liskov Substution Principle example?

I just wanted to check that I understand the LSP correctly and can solve it. I am taking the classic rectangle/square problem and attempting a solution: class Rectangle{ public $width; ...
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1answer
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How to verify the Liskov substitution principle in an inheritance hierarchy?

Inspired by this answer: Liskov Substitution Principle requires that Preconditions cannot be strengthened in a subtype. Postconditions cannot be weakened in a subtype. Invariants ...
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9answers
7k views

Code Smell: Inheritance Abuse [duplicate]

It's been generally accepted in the OO community that one should "favor composition over inheritance". On the other hand, inheritance does provide both polymorphism and a straightforward, terse way of ...
6
votes
2answers
2k views

How does strengthening of pre conditions and weakening of post conditions violate Liskov Substitution principle?

I read that Liskov substitution principle is violated if : Pre conditions are strengthened . Post conditions are eased out. But I don't get fully yet how these two points would violate Liskov ...
33
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6answers
8k views

LSP vs OCP / Liskov Substitution VS Open Close

I am trying to understand the SOLID principles of OOP and I've come to the conclusion that LSP and OCP have some similarities (if not to say more). the open/closed principle states "software ...
2
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2answers
221 views

Do common MVC frameworks violate the LSP and is there a MVC framework which does not?

You who have worked with a framework implementing the MVC architectural pattern most likely know how these frameworks are usually implemented. They contain a base Controller class, which you extend, ...
0
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2answers
59 views

Why is the _replace method of Python namedtuple classes protected?

In the section Method Names and Instance Variables, the Python Style Guide (aka PEP 0008) says, "Use one leading underscore only for non-public methods and instance variables." Why then, does the ...
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3answers
32 views

How to represent the following scenario in a class diagram?

Consider a store with multiple branches and a system generates reports for each branch monthly and annually and an overall report as well monthly and annually. So in total there are 4 types of ...
0
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1answer
62 views

How do you write super() in the UML format?Is it correct to write super(parameter: type): return type in the UML methods section?

Suppose you write a subclass that extends to a certain class and in that subclass, you use the super() method for your constructor. Would you write "super(parameter: type): return type" in the UML?
2
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1answer
127 views

Child class accessing its parent's method from Ancestor method

I find myself right now banging my head with the following issue (in PHP): I have an abstract base class, which has a non-abstract method, inherited and unchanged all over the inheritance chain ...
0
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2answers
565 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) , ...
2
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3answers
83 views

Calling a constructor from a parent class in a derived class

I'm trying to create a parent class with a constructor that takes a single int as a parameter. I also need to derive a child class that creates two instances of the parent class using a constructor ...
3
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6answers
311 views

Can we say “If a parent class never appears in my codes except in its child class, it should be composition instead of inheritance”?

I read some posts about "composition over inheritance","where to use composition/inheritance" , "Is-a relationship..." or "Liskov substitution principle" for some time, but I am not sure if I get the ...
0
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2answers
199 views

Per my design requirements, does this design hierarchy seem reasonable?

Background Construction Note that I am using C# here, but it may not be necessary to provide input to my conceptual questions about design. Consider the following design methodology... I work at a ...
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7answers
338 views

A property that can represent both a single date and a date range: How to properly model that?

I work in a system that can represent a "shipping estimate" in two ways: A specific date: The item is guaranteed to ship at that date A day interval: The item will be shipped "X to Y" days from ...
9
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3answers
249 views

Are Python mixins an anti-pattern?

I'm fully aware that pylint and other static analysis tools are not all-knowing, and sometimes their advice must be disobeyed. (This applies for various classes of messages, not just conventions.) ...
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3answers
191 views

What to do if I need more than one base class in C#? [closed]

Let's say I have a grid with square fields. For the fields I have an abstract Field class. This class has several subclasses, for example EmptyField or RoadField. Some of these fields can be connected ...
2
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1answer
149 views

Creating multiple instances of an implementing class

I currently have an abstract class and multiple classes extending it. My problem is, that there has to be a way to create a variable number of instances of an extending class. The number of instances ...
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1answer
110 views

How to avoid having nested generic in class

I'm working on a side project, and I turned on all rules for code analysis in Visual Studio, and I got the warning notice: Warning CA1006 Consider a design where ...
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1answer
104 views

Is this a misuse of “composition over inheritance”?

The general sentiment seems to be that composition is preferable, in most cases, over inheritance, as it leads to less coupling. But for a case like this, module Publishable def new? ...
3
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2answers
350 views

Cleanest way to expand a base class without explicitly mapping properties in C#

Lets assume I have following base class: public class Base { public int Id {get; set;} public string SomeText {get; set;} public string SomeOtherText {get; set;} public static Base ...
8
votes
4answers
416 views

Parallel hierarchies - partly same, partly different

There are quite a few similar questions out there 1, 2, 3, 4, but non seems exactly the case in this question, nor do the solutions seem optimal. This is a general OOP question, assuming ...
5
votes
1answer
87 views

How do I more effectively design this per its intended design while ensuring I'm meeting SOLID design principles?

I know what SRP is, but am questioning my current design of an object I call an entity. Below is a picture of the design I am referring to. If I shift the code from the GeometricInformation and ...
2
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0answers
208 views

Is it a good practice to use virtual inheritance as default? [closed]

Why virtual inheritance is not used as default? Default as in by the programmer and not the language. If not, why? What are the cases where it may fail? Is there some run time overhead? Is it ...
14
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7answers
38k views

Why are constructors not inherited?

I am confused as to what the problems could be if a constructor was inherited from a base class. Cpp Primer Plus says, Constructors are different from other class methods in that they create ...
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4answers
468 views

Implements > extends, but what about variables?

It's preferable to write programs that depend on interfaces rather than on superclasses, but what if you want a class to have certain variables? Sometimes you want a class to implement a certain ...
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5answers
328 views

Inheritance when following the Repository Pattern in PHP

I am trying to build a PHP application using the Repository Pattern but I'm not sure how I should implement the save method. I have an abstract class called ItemRepository which have the following ...
4
votes
1answer
88 views

Is Python's inheritance an “is-a” style of inheritance or a compositional style?

Given that Python allows for multiple inheritance, what does idiomatic inheritance in Python look like? In languages with single inheritance, like Java, inheritance would be used when you could say ...
0
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2answers
114 views

Best practice for encapsulating a parameter that requires multiple interfaces to be implemented

I encounter this issue multiple times, but I'm never sure how best to deal with it. Basically, some methods I write require the implementing object to support multiple interfaces. The example I have ...
2
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2answers
197 views

What is meant by reuse of inheritance?

A 2013 study of 93 open source Java programs (of varying size) found that While there is [no] huge opportunity to replace inheritance with composition (...), the opportunity is significant ...
2
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2answers
241 views

How much implementation should I provide in an abstract class? [closed]

I have an abstract class AbstractService and about 10 classes that extend from AbstractService. However, I'm not sure how many methods and what methods I should implement in the abstract class and how ...
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votes
1answer
118 views

Inheritance hierarchy design approach - Javascript [closed]

For the below code, that creates inheritance hierarchy, function Animal(){ this.name = "Animal"; // toString is a function in the main Object that every // object inherits from ...
36
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5answers
2k views

How is defining that a method can be overridden a stronger commitment than defining that a method can be called?

From : http://www.artima.com/lejava/articles/designprinciples4.html Erich Gamma: I still think it's true even after ten years. Inheritance is a cool way to change behavior. But we know that it's ...
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1answer
74 views

What actually happens in inheritance (java)? [closed]

class A { int a; int b; A(int i,int z) { a = i; } void abc() { System.out.println("a is " + a); System.out.println("b is " + b); } } class B ...
2
votes
3answers
92 views

Is there particular circumstance that throwing root superclass exceptions is a good practice?

I've been taught that exceptions should be have concise meanings and should contain a message that explains to the client what the exceptional situation is. I am wondering, since I found a piece of ...
0
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3answers
536 views

Using super keyword to access super class members

I have following questions about the super keyword in java: I have a code below with classes: A Extends no class contains integer variable i B Extends class A contains integer variable i C Extends ...
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2answers
482 views

How to solve this inheritance problem

I have the following classes: public abstract class StaticFileController<File, QueryData> : AsyncController { private string _resourceName; public StaticFileController(string ...
2
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1answer
2k 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 ...
7
votes
5answers
459 views

Refactoring three very similar classes using inheritance?

I'm currently working on refactoring the code-base for one of our services. I'm been going through reviewing everything, and I feel it's a bit scattered, and could probably adhere to OOP principles ...