Tagged Questions

A methodology that enables a system to be modeled as a set of objects that can be controlled and manipulated in a modular manner

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3
votes
3answers
467 views

Why shouldn't an object reference have access to a static member in C#

Context of my question: I am reading C#. Trying to understand Static keyword. I understand that when Static is applied to a member of a class, it can only be modified by the class and not the class ...
4
votes
3answers
167 views

Is it a good idea to return a default value if a field in a query cannot be found?

At the place I work we are using a SafeReader class that wraps an IDataReader. One of the 'features' is that if the field you are trying to access wasn't in the query then it just returns a default ...
18
votes
3answers
1k views

Why is a private member accessible in a static method?

The following is pseudo code, I tried it in Java and PHP and both worked: class Test { private int a = 5; public static function do_test(){ var t = new Test(); t.a = 1; ...
-6
votes
1answer
150 views

Does one really need multiple instances of a class? [closed]

Generally I'm extremely skeptical of anyone who criticizes the singleton design pattern in software. In the MVC (model-view-controller) design pattern, views and controllers are usually singletons and ...
2
votes
1answer
179 views

Structuring a storage system for a game

I am working on a multiplayer game, where a player has many storages to store items in. Storage Storage is the system that allows the user to deposit items, and take them back. Example of storage ...
2
votes
1answer
213 views

Design Patterns for creating tasks

I am developing software where each action in my entities need create tasks that will be execute in my infrastructure. When I create a task it is only records in the database. Afterwards, a windows ...
0
votes
2answers
165 views

Good architecture for passing data to multiple APIs

I have a hypothetical scenario where I need to pass data to APIs from multiple different providers, depending on the 'vendor identity' provided by one of the pieces of data. If I have the data as ...
2
votes
2answers
308 views

Project based prefix for class names

My project leader uses project based prefixes for class names, lets say projects name ABC, he create User class name as ABCUser. and he says he do this becasuse if he wants to make User.aspx Users get ...
0
votes
1answer
82 views

When to used static visibility? [duplicate]

I can't attain the primary used of Static Visibility. My question is why they used static method & properties in this code? class PassHash { // blowfish private static $algo = '$2a'; ...
12
votes
8answers
1k views

Mental Models or Real-World-Metaphors for Functional Programming

Does anyone have a good mental model or metaphor for functional programming which references something in the real world? Object Oriented programing intuitively makes sense to me. There are things ...
6
votes
6answers
771 views

How to avoid downcasting?

My question is about a special case of the super class Animal. 1. My Animal can moveForward() and eat(). 2. Seal extends Animal. 3. Dog extends Animal. 4. And there's a special creature that also ...
0
votes
0answers
64 views

Why use subtyped functions?

Say you have arguments A1 >: A2 (contra-variant), and return types B1 <: B2 (covariant). The corresponding functions are such that: A1 => B1 <: A2 => B2 Sometimes, this makes sense to me - ...
36
votes
11answers
4k views

Are error variables an anti-pattern or good design?

In order to handle several possible errors that shouldn't halt execution, I have an error variable that clients can check and use to throw exceptions. Is this an Anti-Pattern? Is there a better way to ...
0
votes
2answers
140 views

Expected error handling

Let's say I have a social media website. On this website, users can upload several pieces of information about themselves, including their phone number. To implement this, I have a class called ...
1
vote
1answer
85 views

Should state machine with synonym states be shown explicitly?

I am new to state machine modeling and while trying to model a system, I have a question. An example will explain it better: Considering a system that does calling (probably a customized cell phone ...
2
votes
0answers
105 views

The inheritance argument of zope.interface (providedby vs isinstance)

What limitations does inheritance of an interface through an abstract base class present that are addressed by zope.interface? In the following talk given in 2010 by Jeff Rush about interfaces, at ...
0
votes
2answers
70 views

putting methods in base class that doesnt make sense/belong there [closed]

I've been lately thinking over design principles and patterns and a question did strike me. Let us say, I want to design a racing game. I want to design the classes for a variety of cars. each car ...
0
votes
1answer
86 views

delegating program logic to lower-level objects

I'm writing a library for use in scientific computing and ran into a bit of a quandary. The types at work here are a class M which consists of some data and a reference to a container class C. There ...
1
vote
4answers
266 views

Combinatorial explosion of interfaces: How many is too many?

I'm a relative newcomer to OOP, and I'm having a bit of trouble creating good designs when it comes to interfaces. Consider a class A with N public methods. There are a number of other classes, B, C, ...
4
votes
3answers
405 views

Is method overriding always a violation of Liskov Substitution Principle?

Overriding a method originally defined in the super class, by definition means this method will do different things when invoked on an object of the base class or an object of the subclass. So does ...
1
vote
4answers
316 views

Circular dependency and object creation when attempting DDD

I have a domain where an Organization has People. Organization Entity public class Organization { private readonly List<Person> _people = new List<Person>(); public Person ...
5
votes
1answer
479 views

Is there an imperative language with a Haskell-like type system? [closed]

I've tried to learn Haskell a few times over the last few years, and, maybe because I know mainly scripting languages, the functional-ness of it has always bothered me (monads seem like a huge mess ...
1
vote
3answers
219 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 ...
2
votes
1answer
82 views

Do objects maintain identity under all non-cloning conditions in PHP?

PHP 5.5 I'm doing a bunch of passing around of objects with the assumption that they will all maintain their identities - that any changes made to their states from inside other objects' methods will ...
0
votes
3answers
117 views

In which object should I implement wait()/notify()?

I'm working in an Android project with multithreading. Basically I have to wait to the server to respond before sending more data. The data sending task is delimited by the flag boolean ...
1
vote
1answer
107 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 ...
3
votes
3answers
214 views

is it valid that a state machine can have more than one possible state for some transition?

I have a requirement for a workflow which I am trying to model as a state machine, I see that there is more than one outcome of a given transition(or activity). Is it valid for a state machine to ...
1
vote
1answer
183 views

Object-Oriented equivalent of LISP's progn function?

I'm currently writing a LISP parser that iterates through some AutoLISP code and does its best to make it a little easier to read (changing prefix notation to infix notation, changing setq assignments ...
3
votes
7answers
677 views

Significant amount of the time, I can't think of a reason to have an object instead of a static class. Do objects have more benefits than I think? [closed]

I understand the concept of an object, and as a Java programmer I feel the OO paradigm comes rather naturally to me in practice. However recently I found myself thinking: Wait a second, what are ...
3
votes
3answers
314 views

Infinite loop with a singleton - does this type of issue have a name?

I ran into an unusual error while working on my project. To better learn from and remember it, I'd like to know if this type of error has a name or some definition. (The error itself OutOfMemoryError ...
5
votes
2answers
240 views

How should I refactor switch statements like this (Switching on type) to be more OO?

I'm seeing some code like this in our code base, and want to refactor it: (Typescript psuedocode follows): class EntityManager{ private findEntityForServerObject(entityType:string, ...
4
votes
1answer
593 views

Why are most GNU's software written in C [closed]

I am a Java developer, and I rarely write GUI program in C. However, I noticed that many GNU's projects, such as PSPP, R, Dia, etc., are written in C, instead of Java or C++. I personally don't mind ...
3
votes
3answers
258 views

How to safely copy an object?

This question is going to be a little long. Please bear with me. Something that happened in a project of mine made me think about how to safely copy objects. I'll present the situation I had and then ...
2
votes
1answer
54 views

Handling Types for Real and Complex Matrices in a BLAS Wrapper

I come from a C background and I'm now learning OOP with C++. As an exercise (so please don't just say "this already exists"), I want to implement a wrapper for BLAS that will let the user write ...
-1
votes
2answers
146 views

what's the point of method overloading? [duplicate]

I am following a textbook in which I have just come across method overloading. It briefly described method overloading as: when the same method name is used with different parameters its called method ...
1
vote
1answer
220 views

Confused about implementing Single Responsibility Principle

Please bear with me if the question looks not well structured. To put you in the context of my issue: I am building an application that invoices vehicles stay duration in a parking. In addition to ...
1
vote
6answers
240 views

“Default approach” when creating a class from scratch: getters for everything, or limited access?

Until recently I always had getters (and sometimes setters but not always) for all the fields in my class. It was my 'default': very automatic and I never doubted it. However recently some discussions ...
0
votes
2answers
135 views

What are the benefits of using a 'decorator factory' that decorates objects?

In a project I decided to implement the Decorator pattern. I have a class Thing with methodA(), and a class AbstractDecorator that inherits from Thing and that all decorators inherit from: ...
1
vote
4answers
261 views

“Collection Wrapper” pattern - is this common?

A different question of mine had to do with encapsulating member data structures inside classes. In order to understand this question better please read that question and look at the approach ...
2
votes
1answer
208 views

Best practice to collect information from child objects

I'm regularly facing following pattern: public abstract class BaseItem { BaseItem[] children; // ... public void DoSomethingWithStuff() { StuffCollection collection = new ...
0
votes
2answers
310 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 ...
5
votes
5answers
633 views

Should I always encapsulate an internal data structure entirely?

Please consider this class: class ClassA{ private Thing[] things; // stores data // stuff omitted public Thing[] getThings(){ return things; } } This class exposes the ...
3
votes
4answers
327 views

Understanding UML composition better

The difference between Composition and Aggregation in UML (and sometimes in programming too) is that with Composition, the lifetime of the objects composing the composite (e.g. an engine and a ...
4
votes
3answers
349 views

Inheritance vs containment while extending a large legacy project

I have got a legacy Java project with a lot of code. The code uses MVC pattern and is well structured and well written. It also has a lot of unit tests and it is still actively maintained (bug fixing, ...
0
votes
0answers
88 views

Is this considered an implementation of the Template Method design pattern?

Please consider a StringBank class. This class holds a list of Strings and can return them to the client. It's code (irrelevant stuff omitted): abstract class StringBank{ List<String> ...
1
vote
1answer
102 views

How to properly handle conditional dependencies in a factory?

Let's say you have a string $action run-time, that specifies which type of $object needs to be created: $dbobject, $memcacheobject, $fileobject, $xmlobject, etc. Assume also, that creation of an ...
3
votes
2answers
237 views

Does this Decorator implementation violate the Liskov Substitution Principle?

Please consider the following implementation of the Decorator design pattern: WordBank objects store strings and return them to the client through the method getWords(). The decorator class, ...
1
vote
2answers
163 views

Three variants of circular references between objects: how to choose?

I'm designing an object dependency graph of my program and one ambiguity between design variants appears from time to time. Imagine two objects having a reference to each other. Obviously, at least ...
5
votes
1answer
603 views

Is this actually good OO design?

Context I have Specification class with several properties including: StartDate, EndDate, DaysToComplete, DateToComplete. A specification contains a list of required courses (i.e. a company requires ...
0
votes
4answers
196 views

Why encapsulate container variables? [duplicate]

I wasn't sure how to formulate the title, but there's something that's made little sense to me in OOP I understand the idea of encapsulation, which is to create a layer of protection, and ...