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

learn more… | top users | synonyms (1)

1
vote
2answers
609 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
votes
5answers
12k views

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
votes
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
votes
2answers
10k views

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
votes
3answers
731 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
vote
1answer
594 views

How do we structure our JavaScript so that it is easily editable, testable, and can make calls to render a view without knowing specifics about it?

I am working on a web application that displays some data and uses JavaScript. Right now, we are serving up parts of our JavaScript code (to display certain types of information, that is, "Render a ...
78
votes
3answers
17k views

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
votes
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
votes
1answer
583 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
votes
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 ...
26
votes
2answers
21k views

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 - ...
5
votes
4answers
1k views

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
votes
3answers
941 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
votes
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
votes
1answer
759 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
votes
3answers
4k views

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 ...
1
vote
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
votes
7answers
878 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
votes
3answers
443 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
votes
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 ...
16
votes
3answers
2k views

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 ...
3
votes
4answers
3k views

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, ...
2
votes
1answer
347 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 ...
5
votes
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
votes
2answers
358 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
votes
2answers
136 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 ...
2
votes
2answers
226 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 ...
1
vote
2answers
93 views

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: ...
24
votes
6answers
2k views

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
307 views

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 ...
68
votes
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
votes
2answers
463 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
votes
1answer
544 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
votes
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 ...
2
votes
4answers
1k views

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
339 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 ...
2
votes
2answers
595 views

Pattern for loading and handling resources

Many times there is the need to load external resources into the program, may they be graphics, audio samples or text strings. Is there a patten for handling the loading and the handling of such ...
0
votes
2answers
1k views

What's the point of the Prototype design pattern?

So I'm learning about design patterns in school. Many of them are silly little ideas, but nevertheless solve some recurring problems(singleton, adapters, asynchronous polling, ect). But today I was ...
4
votes
1answer
122 views

Design pattern for isomorphic trees

I want to create a data structure to work with isomorphic tree. I don't search for a "algorithms" or methods to check if two or more trees are isomorphic each other. Just to create various trees with ...
2
votes
2answers
3k views

IoC containers and service locator pattern

I am trying to get an understanding of Inversion of Control and the dos and donts of this. Of all the articles I read, there is one by Mark Seemann (which is widely linked to in SO) which strongly ...
4
votes
2answers
1k views

What patterns book for iOS development contains this specific information? [closed]

I've read several books on iOS development and Objective-C, however what a lot of them teach is how to work with interfaces and all contain the model inside the view controller, i.e. a ...
9
votes
1answer
2k views

Useful design patterns for working with FragmentManager on Android

When working with fragments, I have been using a class composed of static methods that define actions on fragments. For any given project, I might have a class called FragmentActions, which contains ...
1
vote
1answer
296 views

Is there a good design pattern for this messaging class?

Is there a good design pattern for this? I want to create a messaging class. The class will be passed: the type of message (eg. signup, signup confirmation, password reminder etc) the client's id ...
1
vote
1answer
143 views

Am I missing a pattern?

I have a class that is a singleton and off of the singleton are properties that hold the instances of all the performance counters in my application. public interface IPerformanceCounters { ...
2
votes
2answers
775 views

Liskov substitution and abstract classes / strategy pattern

I'm trying to follow LSP in practical programming. And I wonder if different constructors of subclasses violate it. It would be great to hear an explanation instead of just yes/no. Thanks much! P.S. ...
3
votes
2answers
5k views

Using PDO with MVC

I asked this question at stackoverflow and received no response (closed as duplicate with no answer). I'm experimenting with OOP and I have the following basic MVC layout: class Model { // do ...
3
votes
2answers
638 views

Design backward and forward button operations of a browser

If you were asked to design the backward and forward button operation (as a library) in a browser, how would you do it? What will be your APIs and parameters to them? what data structure will be best ...
2
votes
2answers
2k views

Design Patterns - Service Layer

I currently reading a lot about Design Patterns and I have been watching various Pluralsight videos from their library. Now so far I have learnt the following: Repository Pattern Unit of Work ...
5
votes
2answers
6k views

How to handle sorting of complex objects?

How would one sort a list of objects that have more than one sortable element? Suppose you have a simple object Car and car is a defined as such: class Car { public String make; public ...