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

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Bridge Design Pattern - I still don't get it [duplicate]

Possible Duplicate: Understanding the bridge design pattern I have read lots of material about the bridge design pattern: ...
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4answers
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Abstracting out a module or using the Module Singleton directly?

I am working on a module which is dependent on other module for some functionality. Now the dependent module provides a lot of functionality and I need only few of them, hence got the idea to create ...
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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: ...
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2answers
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Changing __class__ in a factory?

I'm parsing a set of XML files of different kinds (these kinds are known in advance). These are my requirements: I want an object to represent each XML document (object-xml mapping) I'd rather ...
10
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4answers
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In MVC, can/should basic data retrieval from the Model be done in the View?

Given the concept of 'skinny controllers, fat models' and the general acceptance that Views can directly call on Models when requiring data for output, should one consider handling the 'get and ...
38
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2answers
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What is the purpose of NaN boxing?

Reading 21st Century C I arrived at chapter 6 at the section "Marking Exceptional Numeric Values with NaNs", where it explains the use of the bits in the mantissa to store some arbitrary bit patterns, ...
7
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2answers
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POST/Redirect/GET with invalid form submission?

In the field of web development, is it good practice to do a POST/Redirect/GET when fields in a form submission are invalid, as well? Typically, no sensitive transaction would have taken place, in ...
12
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1answer
22k views

Design pattern for object conversion (java)

I don't use design patterns very often, besides an occasional factory and MVC, and I want to start using them more. I have a concrete case at hand that I would like your opinion on the use of design ...
6
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2answers
3k views

Visitor stability vs instanceof flexibility

I am working on a GUI application which generates a configuration file. I have a class hierarchy for the configuration model and I use an object tree of that hierarchy in several different contexts. ...
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3answers
417 views

Hacking Python “Requests” library.. How to start as an intermediate pythonista?

My question is conceptual, yet extremely vital for me. I'm an intermediate Python developer. I know fair enough about it, and actually use it on a daily basis. Now, I would like to transform my ...
5
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2answers
2k views

Service layer design

I am developing an MVC website in PHP, and for the first time, I would like to implement a service layer. I have some design considerations I would like to get some advice on. The backend will by no ...
3
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2answers
144 views

Determining which decorator classes are available via reflection

I'm creating a pizza place application where employees will be able to create orders for customers(pizza and any number of toppings). This is for a school project but the requirements have nothing to ...
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3answers
235 views

terms for the html/css/javascript model?

Are there any words for the design model implemented by HTML + CSS + JavaScript, either for that specific set of technologies or any abstract pattern that they follow?
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600 views

Class structure/pattern for validating several different Excel templates?

I'm trying to validate the contents of Excel sheets that follow several different templates. For each one, there are three possible validation actions for various cells: Regex (e.g. "XYZ-123" fails ...
21
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5answers
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success:/failure: blocks vs completion: block

I see two common patterns for blocks in Objective-C. One is a pair of success:/failure: blocks, the other is a single completion: block. For example, lets say I have a task that will return an object ...
14
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3answers
11k views

How to make an ASP.NET MVC site modular

I'm in the planning stage for an employee intranet system to be built with ASP.NET MVC 4. We'd like the site to consist of separate "modules", each of which provides a different feature: messaging, ...
10
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2answers
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Implementing the command pattern in a RESTful API

I'm in the process of designing an HTTP API, hopefully making it as RESTful as possible. There are some actions which functionality spreads over a few resources, and sometime needs to be undone. I ...
11
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3answers
724 views

Is using unit tests to tell a story a good idea?

So, I have an authentication module I wrote some time ago. Now I'm seeing the errors of my way and writing unit tests for it. While writing unit tests, I have a hard time coming up with good names and ...
1
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1answer
546 views

How to structure our Javascript so that it is easily editable, testable, and can make calls to render a view without knowing specifics about the view

I am working on a web app that displays some data and uses javascript. Right now, we are serving up parts of our js (to display certain types of information, ie "Render a View") via our server which ...
78
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3answers
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What is an Anti-Corruption layer, and how is it used?

I'm trying to figure out what the Anti-Corruption layer really means. I know that it's a way to transition/work around legacy code or bad APIs. What I don't understand is how it works and what makes ...
17
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3answers
3k views

How to design website workflow?

I have been thinking about this for really long time without reaching an optimum answer. First of all, I'm a medical doctor who loves programming but never really studied it, except for home learning ...
2
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1answer
570 views

Does it make sense to create a Ruby wrapper to reference a Java object that does exactly the same thing?

I am using JRuby. In my Java code, I have a class called Texture, capable of doing some graphic manipulation stuff. In my Ruby code, I will usually need to draw things, so though I should simply ...
11
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1answer
3k views

Are we using the repository pattern right?

We are using a bunch of separate classes suffixed with -repository to retrieve the data from the database; for each table its own repository. We have for instance a customerrepository class which has ...
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2answers
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MVCS - Model View Controller Store

I recently decided to start learning iOS Development, and to this end I’ve been reading iOS Programming: The Big Nerd Ranch Guide. In the book the authors describe a design pattern MVCS - ...
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4answers
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Is there something like a polymorphic Singleton?

I have a resource loader object that loads objects from the disk or from a ZIP archive, depending on the platform. It has state (e.g. the path to the directory or the ZIP archive, and possibly some ...
4
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3answers
937 views

Is there a design pattern to solve this problem?

I've been struggling with a design so I figured I'd ask here and see if anyone's able to help :) High level overview I'm designing an app to gamify exercise by creating mini competitions (ex. Who ...
2
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1answer
312 views

In JSF where do objects like PhaseListeners fit in the MVC pattern?

When it comes to JSF, I've had trouble distinguishing where certain objects I create fit into the overall MVC pattern. The View is simple enough since that's handled by the .xhtml template but when ...
3
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1answer
738 views

Java Logfile Parsing Assistance

I'm writing a log parser that continuously looks for specific patterns and then fires off events to another system when it finds these matches. The firing of the event is time critical to catch errors ...
9
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3answers
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How do you handle multiple users editing the same piece of data in a webapp?

There's a project I'm working on that is looking to produce a web application that will manage a task list between multiple users. This is a master task list whose task items get distributed by an ...
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1answer
90 views

How to get a reference to a central AssetLoader in every Widget?

I'm working on a simple UI system for a game. The building blocks are Widget objects, which can contain each other. There are several sub classes of Widget, e.g. LabelWidget, ImageWidgetand ...
10
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7answers
856 views

Is the use of security conditionals in a view a violation of MVC?

Often what's displayed to a user (e.g. on a web page) will be based partly on security checks. I usually consider user-level / ACL security to be part of the business logic of a system. If a view ...
4
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3answers
438 views

How to refactor “nested” view classes to avoid deep method calls?

Lets say I'm displaying a bunch of data (model) using a View class for rendering. However, a lot of the data has sub-data (models) complicated enough to require separate rendering classes. In my ...
8
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3answers
3k views

When is Efferent / Afferent coupling good or bad

I have a software patterns exam this week and one of the topics we are to study is Efferent and Afferent coupling. I understand a package has a high Ce (efferent coupling) if it depends on a number ...
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Does the state Pattern violate Liskov Substitution Principle?

This image is taken from Applying Domain-Driven Design and Patterns: With Examples in C# and .NET This is the class diagram for the State Pattern where a SalesOrder can have different states during ...
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4answers
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Good design pattern for a c++ wrapper around a c object

I have written an extensible c++ wrapper around a very hard to use but also very useful c library. The goal is to have the convience of c++ for allocating the object, exposing its properties, ...
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1answer
340 views

Why does Java MessageDigest.getInstance() have a String as a parameter?

I presume it's that way so it could be extended with custom algorithms, but wouldn't it be more convenient to apply, let's say, factory method pattern here and avoid the whole NoSuchAlgorithmException ...
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4answers
2k views

Are immutable/stateless singletons bad?

Lately there have been some kind of revolution against singletons, but is there something wrong with them if they are stateless? I know the overuse talk and all... this applies to everything not just ...
8
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2answers
352 views

event listener pattern in api - what should adding the same listener twice do?

In designing an API that provides an event listening interface, it seems there are two conflicting ways of treating calls to add/remove listeners: Multiple calls to addListener will only add a ...
0
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2answers
133 views

2 different tasks in template method

I've read about Template Method Pattern but I'm not sure about one thing. The steps (methods) of an algorithm are supposed to be in the template method. In the case my template method's algorithm is ...
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2answers
225 views

Designing entities to be self-manageable

Although this is a gamedev project, the question is about general OOP practices, so I believe it goes here. Here's the problem: (note: I will call any equivalent of real-world physical objects ...
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Mingling DB transactions and logging from a design perspective

Say we have a view page where users perform actions in multiple steps, some of these actions would involve DB operations with transactions (the snippets are in pseudo-code like from): View 1: ...
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6answers
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How do I prevent unknowningly duplicating code?

I work on a rather large code base. Hundreds of classes, tons of different files, lots of functionality, takes more than 15 minutes to pull down a fresh copy, etc. A big problem with such a large ...
0
votes
2answers
1k views

Designing a Web Application with Two Different Backend Databases [closed]

I'm working on a pretty standard LAMP based web application. The server itself has a standard MySQL database and the application is written in PHP. The kicker is, we also use SQL Server databases ...
5
votes
4answers
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What pattern should one use to dynamically add multiple small views to one big main view?

Imagine a small calculator GUI, with basic operations (+,-,/,*), and in the menu we can check for example scientific calculator and a small new view with the extra functions appears beside. I was ...
67
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2answers
8k views

Are there any OO-principles that are practically applicable for Javascript?

Javascript is a prototype-based object oriented language but can become class-based in a variety of ways, either by: Writing the functions to be used as classes by yourself Use a nifty class system ...
4
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2answers
458 views

DDD and filtering

I am developing an app in ddd maner. So I have a complex domain model. Suppose I have a Fare object and Airline. Each Airline should contain several or much more Fares. My UI should represent Model ...
7
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1answer
539 views

Domain Model and Querying

I am new to DDD, having worked only in Transaction-Script apps with an anemic model, or just Big Balls of Mud, so please forgive any terminology I abuse. I am trying to understand the proper ...
5
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3answers
2k views

How to create a manager class without global variables nor singletons?

I would like to implement some kind of manager class in my application. It will be in charge of loading textures, processing them, distributing them etc... At first, I wanted to make a global ...
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4answers
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Switch interface implementation using configuration [closed]

We want to allow the same core service to be either fully implemented or, as other option, to be a proxy toward a client legacy system (via a WSDL for example). In that way, we have both ...
6
votes
5answers
336 views

design for interruptable operations

I couldn't find a better topic but here it is; 1) When user clicks a button, code starts t work, 2) When another button is clicked, it would stop doing whatever it does and start to run the second ...