A design pattern is a general reusable solution to a commonly occurring problem in software design.

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How to deal with interactions between many objects

I've been working on a game in my spare time. I'm pretty much done defining the primitives and until today everything was pretty well segmented and encapsulated but now it's come time to implement ...
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2answers
60 views

Visitor only applicable when using the Composite pattern?

For a long time I've tried to get my head wrapped around the visitor pattern, and somehow this thing keeps being rather fuzzy to me. I'm currently under the impression it is only useful to apply ...
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43 views

Functional programming equivalents for the following [duplicate]

I am trying to make the leap from functional programs for "hello world" equivalents to more real-world applications. As I come from a Java world and have been exposed to all it's design patterns, my ...
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3answers
66 views

Relative encapsulation design

Let's say I am doing a 2D application with the following design: There is the Level object that manages the world, and there are world objects which are entities inside the Level object. A world ...
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1answer
84 views

Adding field to the class at runtime - design pattern

Imagine your customer want's to have a possibility to add new property (e.g. color) to product in their eshop in their CMS. Instead of having properties as fields: class Car extends Product { ...
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0answers
57 views

Best approach for tracking dependent state

Let's pretend I work on a project tracking application. The application is a database backed, server hosted, web application. In this application there are Projects which have many Activities which ...
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2answers
418 views

When is it worth NOT using a Factory?

I'm employing TDD quite a bit these days and really enjoying myself - everything seems to flow better and be naturally better constructed and organized. However, while writing a bit of IO code, ...
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2answers
204 views

Can this argument be enough?

We have two C++ classes named Important and Small The class Small use a few methods and attributes from the class Important, but not all. Since our application is performance critical, instead of ...
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0answers
29 views

Developing “Question asking framework”, like surveymonkey — looking for ideas [closed]

I am developing a generic "Question asking framework" which will ask several questions and collect their responses. I would like to read some blog posts about this, if there are any, in order to get ...
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5answers
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How would another popular language avoid having to use the factory pattern while managing similar complexity as in Java/Java EE?

Factory pattern (or at least the use of FactoryFactory..) is the butt of many jokes, like here. Apart from having verbose and "creative" names like ...
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0answers
85 views

Help finding good design/architecture patterns for systems integration [on hold]

There are several programs written at my company that to some level automatically configures systems. The systems that are configured by the programs can sometimes be the same but are most often not. ...
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1answer
144 views

How to make my code decide which class to instantiate based on a parameter?

I have a system in which I will perform queries to a database. I want Query1, Query2 and Query3 to use the same methods in their way to the data source layer. To do that I would like to make ...
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2answers
190 views

Design Pattern: Algorithm varies according to the input arguments

I will give a simple example to help you understand my question. Suppose we have a rectangle and a Utility class with a method that creates a buffer arround a shape. The .createBuffer method has ...
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1answer
140 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 ...
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1answer
139 views

Implementing a strategy pattern with dependency injection

Okay, so the goal here is to implement a strategy pattern that can be tested using any sort of automated testing tool. I've been struggling with this problem conceptually for a few weeks now and I ...
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2answers
122 views

Using the Decorator pattern to add public methods to an object

The Decorator pattern is usually used to extend the functionality of an object by extending one of it's current methods. To illustrate, please consider an object object and a decorator decorator. ...
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0answers
59 views

Java: Singleton Event Driven Design [closed]

I have a singleton class ( I make this as immutable ). This class is present in the base module. It has a static method getInstance() which will initialize a new object based on the data stored in a ...
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4answers
139 views

Why would I want a UnitOfWork layer if my service/business logic layer is specific enough?

I'm getting into the Repository pattern (which I love), and as I read up on it I see this UnitOfWork pattern in many articles. Before I knew anything about UnitOfWork I was just using my Repository ...
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1answer
136 views

Functions returning either “OK” or “error message” instead of procedures

I have joined writing middle-size multi-purpose database application as co-lead. It currently has about 150 tables (and growing) and overall functionality you can imagine as very small ERP. At many ...
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2answers
130 views

Refactoring sought for replacing shared data types in .NET component

I am in charge with updating a software product that is made up of two components the Controller process and the UI process. The Controller and the UI communicate via XML messages. Furthermore, the ...
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1answer
85 views

Design MVC site such that UI developer can work without access to data tier? [closed]

I'm working on an ASP.NET MVC site (using Team Foundation Service for source control) that I've divided into a few separate projects under one solution: Project.WebAPI (Main entrypoint, contains ...
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3answers
328 views

What is the main goal of MVVM pattern? [closed]

Could you tell me what is the goal of the MVVM pattern? What are the arguments or the reasons I can give to a team and product owner to respect and develop according to this pattern? I would like a ...
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2answers
180 views

Is it wrong to have HTML strings within PHP objects, or is it only wrong in controllers?

I've always thought that in typical MVC design it is bad practice to build & concatenate HTML strings in any PHP file or class that isn't strictly a template. I'm working on a large project with ...
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11answers
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Ensure that each class has only one responsibility, why?

According to Microsoft documentation, the Wikipedia SOLID principe article, or most IT architects we must ensure that each class has only one responsibility. I would like to know why, because if ...
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4answers
199 views

What are the perks and drawbacks of using html templates versus building the html in-code [closed]

As far as I can see there are two ways of building a html page: "inside" the language (I'll call it building for lack of a better name) or outside the language (using templates). Let me explain a bit ...
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2answers
65 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
101 views

Differentiating between Factory Method and Abstract Factory

I've been confused for a while about the differences between the patterns Factory Method and Abstract Factory. Been doing a lot of research, still confused. I have one question: Is the only ...
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1answer
97 views

design patterns in Javascript - toggle functionality [duplicate]

My goal is to add some functionality to the bxslider script - in this case, I want to be able to enable/disable a keyboard event handler AFTER a slider is instantiated. I guess this code is self ...
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2answers
64 views

Container/Item pattern without `friend`

I have a class Container containing objects of type Item. They are different classes, and especially they have no common base class (e.g. a Container does not itself have a Container).: class ...
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1answer
154 views

Observer pattern: “Web of observers” - Is this ever in use?

I had an idea (which I'm sure already exists), to create a sort of 'network of observers/subjects'. I would like to describe how it works and than ask several questions about it. Say we have 5 ...
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1answer
54 views

Is it fine for a class that creates objects to delegate them?

I have a large list of intercommunicating components; so I decided to have one class create all of them and then subsequently delegate them to other classes to facilitate finer tweaking and wiring ...
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1answer
151 views

Python - Is this a bad strategy pattern?

I've got a Python project wherein a basic object is created and various different attributes are modified/given to it via what I thought was a good example of a strategy pattern. In this silly game ...
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0answers
44 views

How to design modular “screen configurator” for database application

I am currently working with a product that is effectively a glorified CRUD application. (It is a C# .NET 4.0 desktop application backed by an Oracle 11gR2 database.) The client program presents a list ...
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1answer
78 views

Design Pattern for Data Validation

What would be the best design pattern for this problem: I have an Object A. Object A can either be registered or deleted from the database depending on the user request. Data validation is performed ...
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1answer
41 views

System Communication: Avoiding Including a Large “HAS-A” Hierarchy Which Isn't Used

The situation: System A Huge, complicated system. Uses an important Message object with many other Message objects attached, many of which have further Message objects attached. In total, this is ...
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Dealing with an often occuring dependency that is not related to the class

I'm using view classes for my templating. These view classes often require the Routing class to get URI's from other pages. You could actually say that the Routing should be available to every view ...
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1answer
151 views

Good pattern(s) for pointing to mutable state

I asked this question once here, but believe the question was unclear. However I'm having a hard time extracting the general problem from my specific case. UPDATE: I've answered my own question ...
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1answer
139 views

Is there a Pattern or a Refactoring Method to pull data-loading out of existing Class

I am refactoring legacy codebase. Part of it is a loadProduct() function inside a larger "everything" class. loadProduct() loads data from a database. I want to move this loading-data part out of ...
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2answers
239 views

What should a repository really do?

I've heard a lot of the repository pattern, but I quite didn't understand what a repository should really do. When I say "what a repository should really do" I'm mainly concerned about which methods ...
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1answer
51 views

Contradiction of layered design and global data access for analytics reporting

While developing an application (mobile app for Android), our team always strives to use best development practices such as interfaces, layering and separation of concerns. When it comes to reporting ...
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1answer
141 views

Is the flyweight pattern a good security choice for managing permissions?

I'm designing a system, and it needs future expandability for the use of a permission system of some kind. I'm wondering if the flyweight pattern would be a good choice to implement this. I'm not ...
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3answers
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How does Observer create loosely-coupled design?

I completely understand the Observer design pattern, what it is for and how to implement it. I also understand what the term 'loosely-coupled' means. But I'm not sure how Observer makes designs more ...
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Looking for design pattern to represent shared state in music sequencer

I like to give lots of context, but also to state the basic question up top as concisely as possible. Feel free to read a little or a lot. I'm working on a music sequencer, and have been happy so far ...
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3answers
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Question/Answer for multiple Users - How should I design it?

I'm wondering about a good way to deal with a Question/Answer - Model for multiple Users. My goal is to have an efficient and readable model where all the results of my users are stored. Every user ...
4
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3answers
298 views

Model-View-Controller: Does the user interact with the View or with the Controller? [closed]

I have recently learned about the MVC design pattern. I'm learning from the Head First Design Pattern book. According to this book (if I understand correctly): The Model is most of the application ...
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2answers
117 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. ...
2
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6answers
300 views

Design pattern for method to accept one of several static items in C#?

I want to illustrated my question by way of a (hopefully) representative example. Lets say I have a situation where I am developing a class library in C# to be used in some simulations. I want to ...
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0answers
82 views

Run a function when a function in a list is executed?

Goal: I'm currently doing an MVC project and I have this method to update the ViewBag (based on previous actions of the user). I would like to call this function whenever a certain list of MVC Actions ...
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1answer
55 views

How to design a scriptable communication emulator?

Requirement: We need a tool that simulates a hardware device that communicates via RS232 or TCP/IP to allow us to test our main application which will communicate with the device. Current flow: ...
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120 views

Why does the Mailbox app need their own backend?

I am only coding in Objective-C and I have no experience with backend coding, only a high-level understanding. I understand why a lot of programming projects require backend servers but I'm not ...