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

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Deploying and maintaining a script on customer's domains

I am trying to figure the best way (or just the pros and cons of various options) for delivering a service via a script which runs on the customer's site (think Google Analytics). Unlike Google ...
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1answer
289 views

Is Activity/Fragment already a presenter?

An Activity or a Fragment is where you handle the logic of updating views with model data. However, they are tighly coupled with the Android's framework. Are these classes already presenters? ...
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2answers
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MVC controller and decoupling explained

In this article you can see that View has (uses or aggregates ) controller and ConcreteView has Concrete model. public abstract class View { public abstract void Update(); private ...
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736 views

Reducing the complexity of a class

I have looked at some answers and searched on Google, but I could not find anything helpful (i.e., that wouldn't have awkward side effects). My problem, in abstract, is that I have an object and need ...
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Does a pattern for “houskeeping” a NoSQL DB with eventual consistency exist?

I'm working with a NoSQL DB with eventual consistency. My software is not only inserting Java Objects in JSON but also creating secondary indices for cross-referencing and similar things. Due to the ...
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2answers
166 views

Design pattern how to deal with objects validation?

I am thinking if is there some design pattern to work with objects and its states. In my REST API I have a access token objects, these objects contain information about authenticated clients: public ...
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1answer
48 views

Call methods of subclass when iterating over base type collection [duplicate]

Imagine this code: using System; public enum BaseClassType { DerivedA, DerivedB } public abstract class BaseClass { public BaseClassType Type; public BaseClass(BaseClassType type) ...
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1answer
107 views

Single tracking algorithm for many carriers [closed]

When it comes to tracking packages from a multitude of carriers, is it possible to wrap a globally accepted way of pulling tacking status or must I write support for each carrier we deal with? I have ...
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5answers
282 views

Inheritance when following the Repository Pattern in PHP

I am trying to build a PHP application using the Repository Pattern but I'm not sure how I should implement the save method. I have an abstract class called ItemRepository which have the following ...
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1answer
152 views

What approach in DataMapper Pattern is better for multiple or joined tables?

Normally, a Data Mapper maps data of one particular table. (Theoretically it should be communicating between Storage and a Domain Object, but its not possible in my case, so I am directly ...
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59 views

object configured by another class

Below I describe what I'm trying to do and how I think I will do it. What I'm hoping is that a design pattern exists for using one object to configure another. This would allow me to have a nice ...
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2answers
173 views

Maintaing drop down lists for the application

What would be the best approach to maintain the dropdown lists for the whole application (like city, state etc) taking into account the SOLID principles and performance? Right now am loading the list ...
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2answers
322 views

Sending Exceptions as event arguments

Is it a good idea to send Exceptions as EventArgs in C#? (And not actually throw the Exception). I have a class that performs a long running asynchronous task. If something goes wrong in the middle ...
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Fill widget with data retrieved from internet

I want to retrieve data from internet and show them into a widget. In particular, I've a widget with a QComboBox containing some service from which I can retrieve a list of exchange markets. When I ...
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2answers
143 views

Who is the Owner of Information? Memento vs. Originator

Imagine for a second that I'm implementing the Memento Pattern, using the following classes. Classes An Originator class that has public and private, properties and fields respectively A Memento ...
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2answers
166 views

Class with only one execution

I'm implementing a long algorithm (about 500 lines of C++). The algorithm consists currently of about 10 different methods. Each method I have to hand over multiple data-structures as parameters, ...
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6answers
226 views

Class design, responsibility granulation, efficiency and performance

I am in a design dilemma. I have a set of data that can be interpreted in numerous ways, but I cannot really decide how finely grained should it be. To illustrate it with some simple code: class Base ...
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1answer
79 views

Manipulating data for a single file

I'm looking for a best practice solution for creating an object whose responsibility it is to handle file storage for a single file. I want to be able to read data from the file, write to the file, ...
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2answers
523 views

Understanding Flux pattern

I'm actually studying the flux pattern and there's something that I can't understand concerning the stores. What are they exactly? I have read many articles, and it seems that it concerns the ...
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1answer
339 views

MVVM with multiple view models that share a model

I have an application where there is an "inventor" model whose data I would like to display differently in different areas of the application. Therefore, I'd like to create different view models ...
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3answers
175 views

How to simplify structure of a monitoring software that uses the Observer pattern?

I am working on a project where I have to monitor the status of an elevator. So far, my design looks like this: We are using a third party library to read and monitor real-time values from the ...
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1answer
387 views

Clean Architecture - How to go from “Database Driven” to “Independent of Database” [closed]

I am looking for some clarity and hopefully some advice on writing clean architecture for a large system. My Companies "Web Solution" is +-10 years old, my job is to rewrite it. It is written across a ...
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2answers
508 views

Is there a design pattern for managing deep many-to-many relationships?

I'm having trouble defining this data pattern I've come across working on several applications. It consists of: An object type which is composed of many objects itself A second object type, where ...
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1answer
182 views

Is it a good idea to have separate UI components make their own webservice calls?

I have few UI components in an angularjs web-application. Each display data based upon same input. One shows stats which are calculated on the basis of a time period. Other shows a chart of daily ...
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244 views

Abstract Alert Dialog Builders (Same Method Calls, Different Objects)

Currently I'm working on an Android library that creates a dialog which allows to select colors from a palette (examples at the end) and I've stumbled upon an interesting design problem. To create ...
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3answers
175 views

DDD design question

I have a question on modelling an Entity\Aggregate root in DDD. I am refactoring a project that uses Entity Framework and business logic as services, the services contain lot of logic which I believe ...
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1answer
64 views

Flux Pattern dispatcher broadcast

I'm trying to get a better understanding of the flux pattern Facebook introduced a while ago. From what I understand the dispatchers dispatches every payload to all registered callbacks. Does anyone ...
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2answers
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Repository pattern with service layer - too much separation?

I have an MVC site which uses the repository pattern. I don't feel like I'm using the MVC style enough, so I'm getting ready to re-architect some of it. But I'm also wanting to do it so if the ...
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Separate settings and implementation class hierarchies

We use XML serialization to store class settings. Each setting-class has (but doesn't reference) corresponding implementation-class. Therefore we can easily make a "settings dll" without any ...
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Pattern for passing in a field as a parameter

I'm writing a Rails app which uses ActiveRecord ORM and a Postgres DB. I've got two attributes which are similar but are separate fields in the database. The assignment and saving of these is kinda ...
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1answer
205 views

How should one model an ExchangeService object (in ews-java-api) for sharing MS Exchange connections?

I am creating an application which uses ews-java-api to connect to an MS Exchange server. Once the connection is authenticated, the api dictates use of ExchangeService object for searching mailboxes, ...
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2answers
856 views

DRY principle in good practices?

I am trying to follow the DRY principle in my programming as hard as I can. Recently I have been learning design patterns in OOP and I have ended up repeating myself quite a bunch. I have created a ...
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4answers
298 views

Good practice for holding immutable data

I'm wondering what is the best practice for holding immutable data, more specifically in C#. For instance, lets say I have an immutable object called Foo. public sealed class Foo { public int ...
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2answers
130 views

Where to put the Country Table?

It might sounds like a silly question but here is my problem. We have 100s of databases and in each of those databases, there is a country table. It was ok this way but we ran into minor problems at ...
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121 views

How to design resilient web service clients?

I am writing an app that is supposed to talk to a web service. Let's say it's a chat app. It would need to receive a stream of new messages (so that they are pushed to the interface as quickly as ...
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4answers
265 views

Strategy pattern and “Is a” relationship

Imagine, I have class IAlgo which is an interface. I have derived from him and implemented his single method called matchCount in different implementations - AlgoA1, AlgoA2, AlgoA3, AlgoB1, AlgoB2. ...
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191 views

UI Design patterns for non-screen based project

I'm working on a small project coded in Python that uses a single button for input and a RGB LED as feedback, which responds to button presses and asynchronous events from the network. As the ...
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1answer
113 views

For DI, where to create dependencies (new objects) specifically within framework code?

Basic requirement I'm making a framework for learning purposes (and likely usage on personal sites). I'm using dependency injection in classes and I'm trying to design where would be a good place ...
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2answers
265 views

Persisting Large/Complex Entities with the Command Pattern — Am I doing it right?

I am in the process of designing and building a large-scale inventory management software-as-a-service that will, hopefully, live a long and fruitful life. Therefore I am exerting a lot of effort ...
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Go - idioms/design for determining when an unknown number of goroutines are complete

I have a workflow wherein I walk recursively through a bunch of directories, then for each file perform some action. I'm using goroutines to walk each directory, and also to process each file. The ...
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1answer
311 views

Thoughts on having a generic, reusable grid viewmodel

I'm developing a wpf-based application and I'm currently struggling to find the best way of supporting a recurring scenario in it. This app uses grids a lot. There are a bunch of features I want in ...
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3answers
141 views

How to understand if a property is a member of a class or I have to create a different class that holds it?

Sometimes when you create a class you can add there several properties (new data members) that you are not certain if you want to do or not. For example, I have a casino slots game. I have tiles and ...
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397 views

Implementing the State Pattern with Object.setPrototypeOf()

Take a look at this implementation of the state pattern in JavaScript: var ON = { switch: function() { Object.setPrototypeOf(this, OFF); this.state = "OFF"; } } var OFF = { ...
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Can a pimpl variation be implemented without any performance penalty?

One of the issues of pimpl is the performance penalty of using it (additional memory allocation, non-contiguous data members, additional indirections, etc..). I would like to propose a variation on ...
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2answers
165 views

How should I structure these Python classes?

Base Class I have a class called Remote. This class represents a remote machine and has properties such as ip, hostname, username, and password, as well as methods for transferring files to/from the ...
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1answer
127 views

How to watch a message queue properly

I have a scenario where I need to 'watch' an Amazon queue. When a message arrives I need to get this message and process it. Right now this is implemented with a do/while and Thread.Sleep when no ...
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1answer
181 views

Class structure for Entity Framework

I'm using EF (Code first) and I'd like to isolate the properties from the methods (many of the methods reference other libraries that I don't want my database project to have to reference). As an ...
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2answers
291 views

How to avoid circular patterns in Node?

I'm new to Node and JavaScript (well, asynchronous programming in general) and I noticed when I was working on a project that the following code is a circular pattern and that these are bad practice ...
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1answer
211 views

Command pipeline design question - where to place validation?

Here is the situation: I have a database and a class that is basically a representation of a set of fields of different tables in it. Let's call it Message. "Message" does not know of the database ...
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81 views

How to better define SRP and “wholesome” objects? [duplicate]

Assume you have a class. It can really be any class that defines a domain concept like an employee, a product on an e-commerce site, or a car. One of those examples that are oldies but goodies. ...