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

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Does it break SRP to have concerns of data handling and object mapping inside a single class, as part of the DataMapper pattern?

Summary I want to look into separating the concern of "creating a populated object from database", to use inside my application. DataMapper pattern seems to be doing just that for me. DataMapper ...
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0answers
25 views

How to authenticate against an API?

In a enterprise distributed system, a user of a web portal can sign into one site, be redirected to a federation provider. Once they log in with, for example, a facebook account, that user is ...
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53 views

Python Classes and Design Questions

What is the best way to design a class to see if an update occurs on a property? I have a whole bunch of classes, and current am going through a re-design of the python package I created. ...
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28 views

Best design for a SQL API - no antlr please [on hold]

As a programming exercise, I'd like to explore creating a simplified sql like api to query csv files. Parsing the files is no problem. My concern is with design. What's the best way to design the SQL ...
4
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2answers
173 views

Is this too much work for a Gateway to do?

I'm writing a Gateway class that wraps access to a web service which provides information about a player's item inventory in a video game. This web service returns a variety of information, however I ...
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1answer
143 views

Single source of truth within an enterprise distributed system

Within an enterprise distributed system I have many services - an ecommerce service, a CRM, support desk, finance, billing. Many of these services share common data, such as Customer data. These ...
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7answers
3k views

How to determine if a class meets the single responsibility principle?

The Single Responsibility Principle is based on the high cohesion principle. The difference between the two is that a highly cohesive classes features a set of responsibilities that are strongly ...
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1answer
283 views

Static methods vs Interface implementation

Here is my problem: I stared to create an e-commerce web site info collector. So I created a parser for each site. The parser class is stateless. I have got methods like: getItemPrice(WebElement ...
4
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2answers
293 views

implementing dynamic query handler on historical data

Context: I have historical data about property (house) sales collected from various sources in a centralized/cloud data source (assume info collection is handled by a third party) Planning to ...
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1answer
93 views

How are the forwarding of requests normally managed in the Chain of Responsibilty pattern? [closed]

I was just experimenting with the Chain of responsibility design pattern, implementing my own version. I'm currently reading Design Patterns, but I'm not really sure whether DP tells to stop the ...
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2answers
324 views

What is the best way to create DTOs from entities and update entities from DTOs in a layered architecture?

Option 1: At first I would make a call to my service layer, which served as an API for my core domain, to get a domain object or a list of domain objects and then pass them into the assembler which ...
8
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3answers
170 views

Reducing boilerplate in class that implements interfaces through composition

I have a class: A that is a composite of a number of smaller classes, B, Cand D. B, C, and D implement interfaces IB, IC, and ID respectively. Since A supports all the functionality of B, C and D, A ...
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1answer
328 views

Pattern to use to relate multiple data sources to different user data widgets

I have an client x server intranet application the basically gets data from the server, format it and send that data to the client for display. At the server we are using ASP.NET C# running on IIS ...
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3answers
101 views

What design pattern is this? [duplicate]

I'm struggling to come up with the name of a design pattern that I need to write about. I've been lead to think it was abstraction but apparently not. Let's say I had a driver class which has a Drive ...
0
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2answers
103 views

in trouble making a card game with pygame

I am designing a card game playable against the computer. The rule is very simple Both player and CPU gets 10 cards of 1 to 10. Player and CPU plays a single card at the same time, every round. The ...
3
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1answer
125 views

Design: .NET web app architecture problem

I'm taking my first foray into .NET and I'm designing a web app that's heavy on other web services right now. I'm intending to do the following: Take user input (a USDOT number) Request data from a ...
4
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1answer
386 views

Using the command pattern for a sequence of tasks

I have a 'sequence of tasks' to undertake on a zip file. It can be simplified into these steps: Validate that the file is a ZIP file and is valid Unzip the file Validate the contents are as ...
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0answers
61 views

Pattern to share fields in inheritance

I'm trying to figure out the best way to solve a design issue. I have to be able to clone (I'm cloning them to Apache HttpClient) different types of HttpServletRequest (POST, GET...) and then send ...
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1answer
75 views

Design pattern for mapping data fields

I have seen this problem a few times and never can come up with a solution i like. System A Sales Order Entity order_id created line_items_count System B Sales Order ...
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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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2answers
290 views

Sharing code logic between controllers, through the Model layer?

As I originally conceived my Model layer, it was only supposed to hold data and no code. I receive DTOs from web-services, they are mapped into my Model objects. Those model objects usually end up ...
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0answers
58 views

How to avoid tying these two methods together with global mutable state?

I'm in the process of reading Code Complete 2 and learned that using global state is a no-no. What can I do to avoid using global state in this situation? Some background information: I have two ...
1
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1answer
102 views

Design Pattern - Adding features to a class

I'm finding myself unable to solve a design problem. For the sake of my simplicity, I'm going to use C# (Web API). Let's say I have an abstract class RestController: public abstract class ...
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2answers
579 views

Is factory pattern a right pattern for the situation described here?

Is factory pattern a right pattern when we want to consolidate the related objects? Problem - In the Set-top box, I have a user-io, basically the interface to control the settop box - The user-io can ...
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6answers
684 views

What are the most used pattern to manage a lot of interconnected parameters?

I recently start to work on an application that drive different measurement device. Before the user start a measure, she sets the parameters of it. Actually, considering all measurements type there ...
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4answers
2k views

Is it ever a good idea to use the design pattern name in the implementing classes? [on hold]

Recently I came across a moderately large python codebase with lots of MyClassAbstractFactory, MyClassManager, MyClassProxy, MyClassAdapter etc. classes. While on the one hand those names pointed me ...
2
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1answer
220 views

When do I reuse or create a new Builder

I've implemented a Builder Pattern in a project I'm working on. I'm using this design pattern to created Fields and Components (div, tables, panel (boostrap)). So I have a Director Component class. ...
2
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1answer
311 views

Change routing to comply with Law of Demeter

I have a Task, Owner and Plan. Charge values are kept in a plan, owner is on a particular plan and task knows its owner. A task needs to setup its charges based on the knowledge the owner has. Owner ...
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1answer
33 views

Filtering additions to a list

Hopefully Iʼm posting this in the right SX, and Iʼve tagged it correctly. I have a legacy system that Iʼm making additions to which contains a custom list object. This list object can contain two ...
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2answers
3k views

Why use Android Fragments?

I have read the documentation and some other questions' threads about this topic and I don't really feel convinced; I don't see clearly the limits of use of this technique. Fragments are now seen as ...
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0answers
35 views

Android: Pattern for checking requirements at startup?

My app's launcher activity checks a bunch of requirements like whether GPS is enabled, there's a network connection, the app has device administrator privileges, etc. Some of these checks display ...
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4answers
150 views

Design Pattern for retry and error handling

I'm trying to find a good design pattern, or perhaps series of patterns, for injecting error handling and retry handling when getting data from a webservice. For instance, I have: do { //get the ...
12
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4answers
970 views

Do I suffer from encapsulation overuse?

I have noticed something in my code in various projects that seems like code smell to me and something bad to do, but I can't deal with it. While trying to write "clean code" I tend to over-use ...
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3answers
73 views

Design question concerning extensibility

I am constructing a new class which handles deciding which class should process the requests from a web service. I'm looking for a solution for a problem that I am having regarding extensibility with ...
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2answers
70 views

Returning a slimmed down domain entity from your view model

I'm wondering how to handle a ViewModel in the traditional sense, which includes both properties and methods, and another "view model" which is simply just the properties -- perhaps the ViewModel ...
3
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2answers
876 views

What is the advantage of implementing a composite design pattern?

Apparently, a composite design pattern represents individual entities and collective entities in the same manner. What is the advantage to this? For instance, if I subclass a class, why would I want ...
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4answers
570 views

Does the Composite design pattern implement recursive behavior?

The Composite design pattern allows us to call an operation() on a 'composite' node in a tree structure, and this operation() will be called on all of the children, subchildren and so on. When an ...
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0answers
81 views

What design pattern best suits managing handles to objects, without passing handles or Manager around?

I'm writing a game in C++ using OpenGL. For those that don't know, with the OpenGL API you make a lot of calls to things like glGenBuffers and glCreateShader etc. These return types of GLuint which ...
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2answers
165 views

Has-A or Is-A or some strategy pattern?

I am developing a web based application which is about tracking Fleet units. Actually i have already developed the system but in the last six years things changed a bit. Ordinary the software ...
4
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1answer
101 views

Separate interface for mutation methods

I've been working on refactoring some code, and I think I may have taken the first step down the rabbit hole. I'm writing the example in Java, but I suppose it could be agnostic. I have an interface ...
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2answers
378 views

Class becoming God Object what pattern to use

I am developing Android app and my MainActivity is becoming God Object. By the way native Activity class implementation is some sort of God Object already. The problem is that my activity class is ...
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84 views

Nested POJOs, exposing collections, detecting changes

I have a couple plain object classes to represent data read from a file. They look something like this: public class Command { private String name; private List<Message> messages; } ...
3
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0answers
44 views

When applying the interface segregation, should you separate interfaces for regular setters and mathematical operations?

When applying the interface segregation, should you have separate interfaces for a straightforward setters and interfaces that perform an operation before setting? For example, say you have a class: ...
5
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1answer
76 views

PHP: Injecting the same database connection into multiple objects

Suppose that there are two classes that define objects of vastly different function such that in the datastore, the information they require is divided into two separate databases. For example, the ...
2
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1answer
357 views

What is better repository design?

I have tables that I insert, delete and update, but I read from views. At times, I may read from the tables as well. What is a better generic interface for a Repository: public interface ...
4
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1answer
427 views

Which patterns/architecture to apply for “Import Data, Process Data, Export Result”

I was wondering which architecture/patterns to choose for the following problem divided into three steps: Import TestScript Description from File (e.g. .xls, .txt) Process Described TestScript ...
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1answer
49 views

Efficient way to handle foreign keys

I am building a script that checks a large network of sites for invalid links. The idea is to flag links that continuously show as not available so that they can be cleaned by the administration team. ...
3
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3answers
650 views

A software design pattern to model runtime-dependent behavior

In a interview I was asked, Suppose we are going to create a software that runs on both desktop machines and smartphones. Name a software design pattern that could be used to enable the ...
2
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1answer
74 views

Expandable alternative to Visitor pattern for tree traversal?

I have a tree containing various subtypes of the my base node class. I now want to traverse this tree and do something with the nodes depending on their type. The most straightforward idea is to just ...
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1answer
75 views

OO Design: Algorithm changing State (Information Flow Question)

I have a class Context, which contains an instance of an abstract class State, which has multiple concrete subclasses (this is an implementation of the State Pattern). Each State subclass executes a ...