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

learn more… | top users | synonyms (1)

0
votes
1answer
185 views

pattern to share objects between API and application

I'm having serious doubts about the design for my Web application. I wanted to separate the business logic from the interface so I made a Web API that handles all the requests to the database. It's ...
2
votes
1answer
138 views

Adapter Pattern: Design Patterns

So far as I know, there are two forms of the Adapter Pattern: the class adapter and the object adapter. Could someone please explain to me the following limitation of the class adapter and why it is ...
0
votes
0answers
30 views

Organizing an image processing pipeline for on-the-fly video analysis

I'm trying to design a system that performs image analysis on video streams from the internet. I have a few rudimentary ideas for how to organize such a system, and I was hoping you guys could ...
3
votes
1answer
79 views

Access items of a container with a pattern

I've two C++ classes with a relation: a container class which has a list of items. For example a library has got many books. The classes are the library and the book. Now from the external world I ...
2
votes
1answer
93 views

What's the right OO way to create a counter/inventory class that works for both differentiated and undifferentiated countables?

You are writing a videogame about trading beans. Red beans, black beans, pinto beans, you name it. As everybody knows all beans are the same. You write the "Inventory" class for a trader in that ...
0
votes
0answers
59 views

Build a map with city blocks and road

Is there a design pattern or well known algorithm to build a simple map with roads and city blocks? To have an idea of what's my target i describe some of the constraints and the context: a matrix ...
2
votes
1answer
68 views

Use adapter pattern for coupled classes

I need (for unit testing purposes) to create adapters for external library classes.ExchangeService and ContactsFolder are Microsoft's implementations in its' EWS library. So I created my adapters that ...
2
votes
2answers
210 views

What do I gain by using the Strategy pattern in this case?

I wrote a program with Java that plays simple music. Currently chords have only one way ('strumming pattern') to be played. I want to expand this and create different 'strumming patterns' that chords ...
0
votes
1answer
79 views

MVC: Where should I store interchangeable algorithms used by the Model (whose names also need to be accessible to the View)?

Please consider a program, where the user chooses an algorithm from a list, and the Strategy pattern is utilized to set this algorithm as the model's operation. For example, an image procession ...
6
votes
1answer
174 views

Javascript MVC application design (canvas)

I'm having difficulty grasping how to structure/architect a canvas application using an MVC like approach in Javascript. UI will be fairly fluid and animated, the games fairly simplistic but with ...
5
votes
4answers
212 views

How to take things step by step

This is about the third time I've had to write software to control a cellular modem. For those unfamiliar with the process, you have a sequence of steps you have to take. Each step takes a certain ...
1
vote
4answers
133 views

Dealing with similar objects with different method signatures

I am fairly new to OO design and have problems with the design of some software and looking for a pattern or a combination of patterns that could help me solving my problem. I have a type that has a ...
1
vote
0answers
77 views

Methods for structuring JavaScript SDKs

I've built a REST API and have been using Backbone models throughout a couple different applications to communicate to it. I would really like to build a single JS SDK that can be used in any ...
0
votes
0answers
55 views

RESTful composition/inclusion of other resources

I have a few HTTP resources, and i'm wondering if including the models of one in the other is acceptable or if there is a cleaner method. In this example, we have a ton of "news" resources, and users ...
0
votes
1answer
159 views

Domain Services vs. Factories vs. Aggregate Roots

After dealing with DDD for months now, I'm still confused about the general purposes of domain services, factories and aggregate roots in relation to each other, e.g. where they overlap in their ...
0
votes
2answers
48 views

Handling ignorable failure conditions in a method

I'm working on a coarse API for performing higher level business functions. Under many conditions these functions may fail in a way that is expected (not exceptional), ie. the function may not be ...
-1
votes
4answers
183 views

Where should you put functions and variables that are only needed by one function in a class?

Say you have a Car class. Properties that make sense for a Car class might be: var make; var model; var year; var turnOn; // a function But the turnOn function is very complicated and ends up ...
1
vote
2answers
90 views

Logging events for reporting purposes

Are there any design patterns or best practices around logging events for use in reporting and BI systems. For example in a system which manages orders from a website, it would be beneficial if a ...
14
votes
4answers
655 views

Progressive Enhancement vs. Single Page Apps

I just got back from a conference in Boston called An Event Apart. A really popular theme amongst the speakers was the idea of progressive enhancement - a site's content should go in the HTML, and ...
0
votes
2answers
182 views

What is the Loopback Pattern? [closed]

I was reading this blog post about Hexagonal architecture and at the bottom it says: The Loopback pattern is an explicit pattern for creating an internal replacement for an external device. When ...
5
votes
1answer
412 views

To Repository Or Not To Repository

When I first learnt about Domain Driven Design, I was also introduced to the repository and unit of work patterns that once seemed to be top notch for the cool kids that threw SQL queries like ...
2
votes
1answer
121 views

Where do utility libraries fit in a layered architecture?

Consider this mock-up of a software stack designed with layered architecture in mind : Every application layer is decoupled through API calls, but a memory handling library is used throughout. All ...
1
vote
0answers
26 views

PaypalCheckout object is composed of PaypalQuery objects. Hide PaypalQuery objects to users of PaypalCheckout?

I have a PaypalCheckout object that handles the checkout process: from initiating API calls, to providing an interface for front-end code (e.g. View/Controller). The PaypalCheckout object handles: ...
0
votes
1answer
102 views

Traversing an AST using Visitors

I'm writing a compiler for a C-like language, and I'm looking for an elegant way to traverse my abstract syntax tree. I'm trying to implement the Visitor pattern, although I'm not convinced that I'm ...
0
votes
2answers
133 views

Optimization ended up in casting an object at each method call

I've been doing some optimization for the following piece of code : public void DrawLine(int x1, int y1, int x2, int y2, int color) { _bitmap.DrawLineBresenham(x1, y1, x2, y2, color); } After ...
0
votes
1answer
130 views

Is the following example a strategy pattern?

In my problem I had lots of objects with slightly different behaviour, but identical attributes and methodes with identical interfaces. The objects variants were quite big in number, and I didn't want ...
0
votes
2answers
51 views

Easiest way to use objects as filters for queries

I'm just starting on a new little pet project of mine. I started the project using a familiar pattern for using objects as "filters" in SQL Queries. I've never been much happy about its easy of use, ...
0
votes
0answers
43 views

Modelling network and persistent entity representations

I have an app where I need to synchronize some entities (simply download latest versions of entities from server to client). Entity has bunch of text properties and bunch of resource links (referenced ...
1
vote
1answer
77 views

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 ...
1
vote
2answers
103 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 ...
1
vote
3answers
147 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 ...
5
votes
4answers
362 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 { ...
3
votes
1answer
103 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 ...
1
vote
2answers
442 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, ...
0
votes
2answers
213 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 ...
18
votes
5answers
3k views

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 ...
1
vote
1answer
164 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 ...
0
votes
2answers
213 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 ...
1
vote
1answer
163 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 ...
0
votes
1answer
178 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 ...
1
vote
2answers
188 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. ...
2
votes
4answers
235 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 ...
0
votes
1answer
154 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 ...
2
votes
2answers
131 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 ...
0
votes
1answer
106 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 ...
0
votes
3answers
381 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 ...
0
votes
2answers
206 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 ...
35
votes
11answers
4k views

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 ...
3
votes
4answers
243 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 ...
1
vote
2answers
81 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, ...