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

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Middleware dependencies

I'm trying to convert a legacy PHP app to use the middleware paradigm, similar to connect/express.js. I've started porting the code into separate middlewares so that every feature is neatly self ...
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3answers
157 views

What is the most efficient way to find a set of locations within a radius of a certain point?

Imagine a dataset of all the restaurants in the US (similar to Yelp, etc), how would you return a set of restaurants within a certain range of a particular zip code. (Assuming you have already a ...
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How can I have objects interacting and communicating with each other without forcing a hierarchy?

I hope these ramblings will make my question clear — I'd totally understand if they wont, though, so let me know if that's the case, and I'll try making myself clearer. Meet BoxPong, a very ...
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173 views

Design patterns for implementing optionally supported features

Here's the original problem. There are two classes: Protocol and, say, ProtocolUser (which actully uses the Protocol class instance). Now, I need to support multiple protocols, whose feature sets only ...
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1answer
126 views

Design pattern for ensuring the “signature” of generic lists is equal

I have an interface, Attribute, that is going to be implemented in various ways, class AttributeA implements Attribute{\\..} class AttributeB implements Attribute{\\..} Then I'm planning to have ...
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Android, access 1 activity from 2 cases, what design pattern is this?

I'm developing an Android app, encounter this case. There are 2 ways we can enter an activity (named activityB): either from activityA or from notification. 1st case: ActivityA -> activityB 2nd ...
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2answers
138 views

Are the Repository Pattern and Active Record pattern compatible?

Currently I am developing a webapp where I have defined models implementing the Active Record pattern. Each model also is defined by an interface that specifies the Entity properties and makes it easy ...
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2answers
144 views

Designing Message class in Java

I'm writing a class for Message. Message comes with Header and Payload. Header has following fields: Version Type For Type "XYZ", the following Payloads are allowed. Configuration Metafile ...
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3answers
109 views

Would implementing a “Throwable Event System” be abusive?

I have been thinking for a couple years now about using Throwable events and implementing a sort of event system that uses throw to dispatch an event, or let a different method handle it with throws. ...
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In javascript, should object properties be declared on top of the function?

I learned that it's good practice to declare variables before they are used. For example: function myFunction() { var i; var j; } Does the same thing go for object properties, and is there a ...
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1answer
54 views

File validation rules

I have an application that can accept CSV files to run some operations. The files look like: CREATE USER:username,last_name,first_name,age user1,Smith,John,23 user2,Poppins,Mary,257 There are a ...
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4answers
559 views

Is Visitor Pattern valid in this scenario?

The goal of my task is to design a small system which can run scheduled recurring tasks. A recurring task is something like "send an email to administrator every hour from 8:00 am to 5:00 pm, Monday ...
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1answer
125 views

Differences in design/thought process for OO in Java and JavaScript [duplicate]

Despite sharing a similar name and syntax, Java and JavaScript are quite different. However, they both have Object Oriented features. As a JavaScript novice, the main differences that I can see ...
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1answer
80 views

Encapsulating mutable objects with special structure in Python

I am writing a library for working with special types of trees, called Foo trees. A Foo tree has very special structure. There some operations, called bar and baz, which only make sense on Foo trees. ...
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2answers
208 views

which one is recommended object-oriented design? [closed]

I made simple object-oriented prgram, and think about design. I wonder which one of belows is recommended object-oriented design. Most left side class is "Main" class. Black arrow means they are "Has ...
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2answers
128 views

how can the presenter or view interact with the model in the MVP pattern?

I'm learning the MV* patterns. MVP in this case. I'm trying to refactor an old android application into the MVP pattern to make things less tightly coupled, but I'm struggling one one concept. I know ...
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3answers
165 views

Design suggestions for converters in Java

I'm trying a set of converters which will convert an object to some older form. And there are different objects which are converted. By older form I mean changing the values of some fields and in case ...
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2answers
51 views

Module based project vs Normal project [closed]

I am writing code on top an established Enterprise application. I see that the application has 4 modules as shown below. -Srk -SrkEJB -SrkUtils -SrkWeb I have gone through the code and I see that ...
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1answer
53 views

What layer would an Audio Player Service fall under in a an MVP system?

I'm trying to completely overhaul an app I wrote a while back that plays audio, and I'm learning how the MVP pattern of organization works, but I'm not sure how/where an audio playback service would ...
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1answer
157 views

Memento pattern: saving memento [closed]

There is one problem about this pattern that troubles me. In a situation when we have to save a state into a file, is it class Memento that should be responsible for handling this process? (for ...
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2answers
283 views

Refactoring long methods with a lot of cyclomatic complexity

I'm attempting to refactor what is becoming a very large method -- currently 350 or so lines -- that contains a high degree of cyclomatic complexity. I understand and ascribe to the theories that ...
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1answer
83 views

Generic PHP web interface for handling concurrent updates optimistically

I'm looking in to writing a new PHP based CMS which handles concurrent edits optimistically like source version control rather than pessimistic locking like Wordpress. I want to be able to write some ...
3
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1answer
275 views

Correct placement of Methods in OOP

Which Class should contain a method which has dependencies on multiple classes? I've coded up a specific example to avoid generalizations. In this example we have an initial requirement : ...
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1answer
120 views

AST processing and usefulness of visitor pattern

I know the visitor pattern is typically used to traverse a hierarchy of heterogeneous objects (inheriting a same abstract object) and dissociate the processing of these objects from the data within ...
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1answer
98 views

MVVM in Photoshop-like application: What object has the responsibility for composing the document?

I'm wondering how an application like Adobe Photoshop, could be architectured to conform to the C+M+V+VM design-pattern, specifically how do you handle the canvas? There would be a Model system which ...
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1answer
269 views

Should all functions be fully self-contained (is it bad practice to share a variable between functions)?

There are two ways to do the same thing (pseudo code) Define databaseHandle in the parent function, and use it as a global in this scope: function API() { function openDatabase() { ...
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1answer
46 views

Polymorphism on repository interface for local and remote operations

I'm in the process of designing a facade ApiClient class that would abstract some CRUD operations between a local database and a remote one (through a REST web app). Said ApiClient class depends on 2 ...
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1answer
111 views

Should I use the State Design pattern for only two states? Also, what if one object's state is affected by another state?

If you only have two states for an object, is it worth it to still use the State Design pattern? The context is a multi-player, turn-based game environment where there are Game "Tables" that a player ...
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1answer
71 views

Strategy pattern can use this pointer?

I want to use strategy pattern, but I wander if it is correct to use "this pointer" with the strategy pattern interface. This is required in order to get internal information which is required for ...
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2answers
120 views

Difference between class scope and object scope design patterns

Apparently design patterns have a ton of classifications. One I am struggling with is whether or not the pattern is a class scoped pattern or an object scoped pattern. Of course no documentation ...
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204 views

Design patterns for navigation between pages on mobile platforms

I'd like to ask you about the best way of handling navigation between pages/activities on mobile platforms. To be more specific - about handling state in more complex apps, about handling 'Back' ...
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163 views

Software pattern for combining properties [closed]

I have two classes that read distinct files. As an examples, two classes, sourceA or Client, and sourceB or Resources: public class Client() { public string ClientName {get; set;} public int ...
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1answer
84 views

What is a context object in relation to a web application?

I've seen the term "context" used in a few web application frameworks but I'm not sure what it's actually about. It seems pretty important and seems to be related to holding session information, but ...
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4answers
822 views

Class Duplication Pattern?

I'm currently working as a solo developer on my current project. I inherited the project from another developer, who has since left the company. It's a model-view-controller style web application in ...
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2answers
60 views

Appropriate Design Patterns [closed]

I have a list of objects which represent log entries like below. List<LogEntry> Entries; //Log Entries Read By A Log Reader The Log Entry Class contains following properties. public class ...
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1answer
41 views

ClickHandler for button = strategy pattern? [closed]

If you provide a implementation of a ClickHandler interface to a button (defining some behaviour), is this the strategy design pattern?
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1answer
108 views

In MVC, who is in charge of handling observers?

(I'm writing a large MATLAB GUI that makes significant use of MVC, so my example is written in MATLAB. However, I believe this question is language-agnostic. Please correct me if I'm wrong.) I have a ...
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2answers
193 views

Is MVC controller an use case controller?

In GRASP (http://en.wikipedia.org/wiki/GRASP_(object-oriented_design) ), a controller (use case controller) is defined as: A use case controller should be used to deal with all system events of ...
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2answers
192 views

Top-down vs Bottom-up approach when designing a class library

I am designing a class library to represent western equal temperament music theory concepts for the purpose of composing notated music with code (I realize there are other libraries and programs for ...
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1answer
152 views

How much trouble can the use of Singleton class as Model cause?

In my latest WPF applications I've been using a Singleton class, that I call Model, to contain all my application's logic, such as file reading, information handling, etc.. In the WPF Views or ...
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1answer
51 views

Pattern to add custom attributes to Forms control classes, without having same code everywhere?

I am creating custom winforms designer. I use label, textbox, combobox, listbox, button and checkbox on the designer. I don't want to show all their properties on PropertyGrid, so I created a custom ...
5
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1answer
387 views

Where we should not use MVC? [duplicate]

I have a software engineering course project that we should design a web application, so I've decided to read about software architecture patterns. I've read a lot about what is MVC and its ...
2
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1answer
110 views

Where to keep persistent services in MVVM architecture?

In an MVVM application I need to use some services that are persistent, e.g. network services like P2P and WCF where the main "engine" or server endpoint must remain up and running during the lifetime ...
2
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2answers
86 views

Sharing info objects between objects?

I'm making a game and I have several cards that are created during the game. Each card needs some info, which is shared between cards of the same type. So I have a class CardInfo, which holds a name ...
11
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3answers
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named arguments replaces the builder pattern

When using a language that supports named and optional arguments, does the builder pattern no longer have a practical use? Builder: new Builder(requiredA, ...
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1answer
117 views

React and simple UI state

I'm starting to playing around with React and have a basic question regarding state. I understand that in React state should only contain data which may change and cannot be computed from elsewhere, ...
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2answers
133 views

Asking about learning experience while working for outsourcing company [closed]

i come up with this question because i feel frustrated to learn new things. When i learn new technologies i can remember it for a short time then if i can't apply to the work i almost forget it. For ...
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2answers
55 views

How to maintain atomicity with a service like pattern

Imagine a route in an MVC web project which handles editing a user of your product. You can do things like change their name, their email, their group, their roles and so forth. This data is put in a ...
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Partially Fulfilled Specification Pattern

We have a model (IPayableModel) with a boolean property indicating that a user may or may not pay for the item. A set of specifications defining criteria that would disqualify the model from payment ...
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4answers
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Architecture: Are form default values considered business logic and where should the logic to calculate them be placed?

An example of default form values on a search form might be: Start Date - Today End Date - The last day of the next month Obviously, these are fairly simple examples, but default values can get a ...