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13
votes
4answers
625 views

Switch vs Polymorphism when dealing with model and view

I can't figure out a better solution to my problem. I have a view controller that presents a list of elements. Those elements are models that can be an instance of B, C, D, etc and inherit from A. So ...
12
votes
6answers
455 views

OO Design, how to model Tonal Harmony?

I have started to write a program in C++ 11 that would analyse chords, scales, and harmony. The biggest problem I am having in my design phase, is that the note 'C' is a note, a type of chord (Cmaj, ...
11
votes
5answers
1k views

Is duck typing a subset of polymorphism

From Polymorphism on WIkipedia In computer science, polymorphism is a programming language feature that allows values of different data types to be handled using a uniform interface. From duck ...
9
votes
5answers
558 views

Writing Testable Code vs Avoiding Speculative Generality

I was reading some blog posts this morning, and stumbled across this one: If the only class that ever implements the Customer interface is CustomerImpl, you don't really have polymorphism and ...
8
votes
3answers
481 views

Two components offering the same functionality, required by different dependencies

I'm building an application in PHP, using Zend Framework 1 and Doctrine2 as the ORM layer. All is going well. Now, I happened to notice that both ZF1 and Doctrine2 come with, and rely on, their own ...
7
votes
8answers
1k views

Introducing polymorphism to new programmers

I've been teaching Java to a group of four people for about four months now. Prior to this, they've all had very limited or no other experience programming. We've gotten through basic control ...
7
votes
4answers
459 views

Design pattern for polymorphic behaviour while allowing library separation

Let's say I have a hierarchy of Item classes: Rectangle, Circle, Triangle. I want to be able to draw them, so my first possibility is add a virtual Draw() method to each: class Item { public: ...
6
votes
4answers
3k views

Replacement for instanceof Java?

So I'm fairly new to programming in the real world (outside of academic projects) and have come across lots of posts saying that using instanceof is a bad thing to use to determine what class a ...
6
votes
4answers
418 views

Besides polymorphism, what's compelling about OOP? [duplicate]

When I first came to OOP (at first in Java, and then C++) after years of working in C and VB, it was amazing. The idea of extending existing behaviour and operating generically over things of related ...
5
votes
13answers
805 views

Limitations of Polymorphism in statically typed languages

I program mostly in statically typed languages, like C++ and Java. A common strategy employed in languages like these to handle dealing with collections of objects which are related, but which need ...
5
votes
3answers
518 views

is down-casting always bad?

At my company, we have many different "services" that work in parallel and send messages to each other using a common messaging system. All message objects are derived from a common generic object we ...
5
votes
1answer
388 views

Abstract Factory Method and Polymorphism

Being a PHP programmer for the last couple of years, I'm just starting to get into advanced programming styles and using polymorphic patterns. I was watching a video on polymorphism the other day, and ...
4
votes
3answers
447 views

Novel polymorphism - any reasons for this code?

As part of my work on a legacy C# application I've come across a novel (to me) use of an interface & concrete implementations. I can't think of any reason why you'd do the following, but I'm ...
4
votes
3answers
439 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 ...
4
votes
2answers
933 views

Is dependency injection by hand a better alternative to composition and polymorphism?

First, I'm an entry level programmer; In fact, I'm finishing an A.S. degree with a final capstone project over the summer. In my new job, when there isn't some project for me to do (they're waiting ...
4
votes
3answers
254 views

Java - Use polymorphism or bounded type parameters

Suppose I have this class hierarchy... public abstract class Animal { public abstract void eat(); public abstract void talk(); } class Dog extends Animal { @Override public void eat() ...
4
votes
2answers
381 views

Reasons behind polymorphism related behaviour in java

I read this code somewhere class Foo { public int a; public Foo() { a = 3; } public void addFive() { a += 5; } public int getA() { ...
4
votes
1answer
1k views

implicit vs explicit interfaces

I think I understand the actual limitations of compile-time polymorphism and run-time polymorphism. But what are the conceptual differences between explicit interfaces (run-time polymorphism. ie ...
4
votes
2answers
248 views

Alternatives to type casting in your domain

In my Domain I have an entity Activity which has a list of ITasks. Each implementation of this task has it's own properties beside the implementation of ITask itself. Now each operation of the ...
3
votes
3answers
946 views

How to setup the c++ rule of three in a virtual base class

I am trying to create a pure virtual base class (or simulated pure virtual) my goal: User can't create instances of BaseClass. Derived classes have to implement default constructor, copy ...
3
votes
2answers
156 views

how to follow python polymorphism standards with math functions

So I am reading up on python in Mark Lutz's wonderful LEARNING PYTHON book. Mark makes a big deal about how part of the python development philosophy is polymorphism and that functions and code should ...
2
votes
3answers
4k views

What is upcasting/downcasting?

When learning about polymorphism you commonly see something like this class Base { int prv_member; virtual void fn(){} } class Derived : Base { int more_data; virtual void fn(){} } What is ...
2
votes
2answers
871 views

Interview question “What is virtual function”

It was funny for me, and I'm interesting the reaction for this question of the community. It was interview for C++/Qt developer, and question was asked "What is virtual function". Not something like ...
2
votes
4answers
485 views

Confusion about inheritance

I know I might get downvoted for this, but I'm really curious. I was taught that inheritance is a very powerful polymorphism tool, but I can't seem to use it well in real cases. So far, I can only ...
2
votes
2answers
464 views

Questions about Polymorphism

So I understand the importance of Polymorphism, including how vital it is. But something I don't quite understand is what about the Constructor and any inherited Class the initial Base Class may ...
2
votes
1answer
102 views

Is it bad practice to encapsulate a single operation in a class? [duplicate]

I recently had a back and forth over at StackOverflow about my answer to this question. The question was simple. The author wanted to transform a number into an abbreviated version that appended a K, ...
1
vote
3answers
336 views

Is it bad practice to check object types with an identifying member variable?

Preamble: I am making a simple board game in C++, in which AI characters move around squares on the board. There are different types of squares, each inherited from an abstract class, each with ...
1
vote
1answer
276 views

What does “polyadic” mean in the context of functional programming and type systems?

And how does it (or does not) correspond to "polymorphic"? Occasionally I see this notion like in: Implement and represent polyadic operations. I checked Wiktionary but it only gives a general ...
1
vote
1answer
543 views

Can the Abstract Factory pattern be considered as a case of polymorphism?

I was looking for a pattern/solution that allows me call a method as a runtime exception in a group of different methods without using Reflection. I've recently become aware of the Abstract Factory ...
1
vote
5answers
143 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 ...
1
vote
3answers
87 views

Refactoring - Utility classes behavior under a common interface

I was suggested to put my question here, so I'm doing so ;) I need a common interface which represents some specific behavior: public interface Contract(){ public void methodA(); public void ...
1
vote
1answer
351 views

Readability vs benefits of polymorphism

We are dealing with a lot of CRUD operations in our application. Each database table has one or more corresponding SQLContainer instances to perform various types of operations. All of these ...
1
vote
2answers
110 views

Interface extension

Suppose that I have an input stream interface, which defines a method for reading data. I also have a seekable interface which defines a method for seeking. A natural way of defining a input file is ...
1
vote
2answers
79 views

Does subtype polymorphism distinguish between inheriting behavior, or inheriting an interface?

To provide some context, I've seen some comments lately that equate inheriting behavior from a supertype, with inheriting a pure interface with no behavior. But there are pretty significant, and ...
0
votes
4answers
465 views

Objective-C message passing related queries

I am learning objective-C after having good knowledge of C/C++. I have 2 questions: Are Obj-C message passing and C++ vtable, two different ways of implementing polymorphism or Are they two very ...
0
votes
1answer
188 views

Does C++ support subtyping?

I know it might be a silly question to ask, but I didn't quite get an a absolute clear answer on this matter, so I thought I'd put it here. Does c++ support the subtyping in the sense that it ...
0
votes
2answers
89 views

Making subclass more type-specific with accessors

I have a super class: TriggerManager with a subclass TimedTriggerManager. NOTE: I'm working in java TimedTriggerManager only deals with TimedTrigger s, a subclass of Trigger. TriggerManager ...
0
votes
1answer
130 views

Polymorphism versus authorization

I have something bother me in the understanding of polymorphism (vs role): Note: I am using rails (but it's a general question) I have 4 models: User Pro Customer Company There is a polymorphic ...
0
votes
1answer
388 views

Java Dynamic Binding

I am having trouble understanding the OOP Polymorphic principl of Dynamic Binding ( Late Binding ) in Java. I looked for question pertaining to java, and wasn't sure if a overall answer to how dynamic ...
0
votes
0answers
71 views

Succinct Lazy Initialization Pattern

Background I often use the following lazy initialization pattern: public class Clazz { private Object object; private Object getObject() { Object object = this.object; if( object == ...
0
votes
0answers
21 views

How would I handle a set of differing event classes with differing handler interfaces in a single event processor?

I'm working on an event processor framework for a simple game I'm writing, in which multiple types of events are handled in a loop. Since these events carry distinct pieces of data (i.e. one carries a ...
-1
votes
4answers
222 views

Polymorphism confusion

I have read once in a book about exception where "an object of type Exception can be an instance of any subclassof Exception". I kinda get it, but there's still confusion can anyone clarify me the ...
-4
votes
0answers
54 views

How to explain Inheritance and Polymorphism to NON CS Students with examples? [closed]

I was wondering if some one could help me with explaining Inheritance and Polymorphism with real world examples to NON CS students preparing for a job interview in a IT firm. PS: My first question on ...
-7
votes
6answers
3k views

Function like C# properties?

I've been thinking about how C# properties work and could work. I know the purpose that C# properties were originally designed for, which is certainly useful. However instead in this question I'm ...