Questions tagged [design-patterns]
A design pattern is a general reusable solution to a commonly occurring problem in software design.
294
questions with no upvoted or accepted answers
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Balance between aggregate boundaries and domain consistency in DDD
Designing an Aggregate and choosing an Aggregate Root getting tricky for me all the time especially when it comes to ensuring right transactional contexts and consistency constraints so I'm wondering ...
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2
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Loose Coupling Presenter to View in MVP
We work in a Java shop here and our web application uses an implementation of the MVP architectural pattern. Our manager comes from a .NET world, where he has been exposed to the MVVM design pattern. ...
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Handling common code among presenters
I'm facing some issues related to code duplication when following MVP architectural pattern in an Android project that I'm working with.
My project structure is separated by packages: data, domain, ...
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Assembler vs Entity Translator and Entities vs DTO
I was hoping that someone could explain the exact difference between an Assembler and Entity Translator.
Martin Fowler describes the Assembler as a sort of Mapper(?) which converts DTOs into Domain ...
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Global variables and common block management in Fortran
Background
The high level overview of my situation is described here. I am breaking it apart into smaller, specific questions, such as this one, regarding extensive use of global variables in a ...
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answer
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Dynamic Object Abilities When Saving State
I have n classes that extends from a State class, the purpose of the State class is to manage the state of the extended classes. For each class we need to save it in the database, remove it and select ...
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Best design pattern/approach for a Factory which needs multiple types of input
I want to develop a Factory of INotifications.
public interface INotification
{
string Text { get; }
string UserId { get; }
NotificationType NotificationType { get; }
}
The problem is, ...
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3
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Designing a flexible search API response
Quick Summary
I'm building a search micro-service that will allow searching across different types of resources in a particular system (e.g. blog posts, users etc.). The API that will be exposed will ...
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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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Environment that enables variable constraint checking and creation
Currently, I'm working on a system that enables users to add Tag's to available TagTypes on specific pages. For instance, we would have a TagType called "Installer" and the user wants his name ...
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Pattern for endpoint that routes requests?
I am building a service that will push notifications to many other services. It has a couple of different notification types that each consumer may care about, but likely will not care about all of ...
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Designing a filtering function
This question is not so much about how to implement a solution as I've already implemented a working solution, but more about how to improve how I implemented it. The implementation process of the ...
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Efficient BACnet device polling strategy
Example BACnet network:
Some help is needed to solve a problem around architecting an efficient method of polling BACnet devices across multiple networks (i.e. MS/TP networks) where client software ...
3
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3
answers
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Do I use Repository or Service Object to Perform Logging?
I'm working in Java Spring, and I have typical service and repository layers. The repository grabs a JSON; passes it along to the service; service maps the repository response to a DTO.
I also need ...
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3
votes
1
answer
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Is Enum Polymorphism bad for DAO Methods?
I have been going back and forth in a discussion about polymorphic enums to call different DAO methods depending on enum entry, and I haven't been able to get a common agreement on this subject.
Lets ...
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How should domain model entities expose information about the current state of their properties?
I'm new to DDD, so please bear with me.
I am trying to design a domain model around an extremely large and complex existing system, where most of the current "domain" logic is either in the UI or in ...
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3
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1
answer
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Data processing pipeline design for processing data
I have a use case for which I need to build a data processing pipeline
Customer contact leads data coming from different data sources like csv, data base, api has to be first mapped to a universal ...
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Python3: How to change the design of a class hierarchy to improve access to objects there buried?
I asked this question already at stackoverflow together with a serialization related part and at codereview for the design part only. Since the design related part receives no answers or comments on ...
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How does "redux" decouple the different components so they can be tested separately in unit tests?
In the past we saw a big move from traditional MVC to MVVM for user interfaces:
One of the primary motivations for MVVM is that the view and viemmodel are competely indepedently of each other and ...
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0
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Memento and releasing resources
Let's suppose we have a class whose state has to be saved and later restored, and we resorted to the Memento pattern for that.
What if the state includes resources that have to be explicitly ...
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Parse track meet output file result
I am building out a parser for a well-known track & field meet management software output file (sample output).
I can parse this manually, and put items into my object model (overview below), but ...
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How to separate data layer from business layer?
My current .NET project looks like below:
Solution (.sln)
--BusinessProject A (.proj)
--BusinessProject B (.proj)
--DataLayer (.proj)
--A separate project calling ExternalService 1 (folder)
--A ...
3
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0
answers
643
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Fetch data in parent vs fetching data in child
I know that I want to develop a React App like so:
<PhotoPage>
<FeedFilter/>
<PhotoFeed/>
</PhotoPage>
Without using Redux, I know that I need to fetch a dataset of ...
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3
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0
answers
91
views
Nested containers with subclasses
I have nested containers A and B. The attributes are there to show that classes have some other members. One of my functions f takes another container of such containers (let's say vector again).
...
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3
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1
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How to set up a sql database to cater for user records, group records and default records?
Outline
I have an application that loads data from a database. I'm not talking about client data here though, I'm talking about application configuration. The database will therefore come with some ...
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Dependency Injection and class Inheritance
The project I am working on for about a year now was used to create a new mysqli connection to the database each time there was a Query to the database. In order to quickfix this problem at places ...
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Two-way adapters
In GoF there is a two way adapter concept:
A potential problem with adapters is that they aren't transparent to
all clients. An adapted object no longer conforms to the Adaptee
interface, so ...
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3
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answers
321
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Anemic Domain Model Developer thinking about a rich domain model
Martin Fowler talks about the Domain Model where the Business Logic Layer contains classes that contain state and behaviour. As far as I am concerned this means:
1) Controller calls a class in the ...
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483
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Mocking third party web service
I am working on a project to create a wrapper library which will be used to interact with a web service provided by the client's IT team. The reason for this library is that we interact with this ...
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Multiple inheritance in ASP.NET MVC Controller
In one case BaseWizardController should implement background functionality of BaseController->BaseConsumerController, in other case it should implement only BaseController.
Any ideas how can I do ...
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Building a generalized notification system: passive vs. active
Recently, I've tried my hand at building a notification system, but I quickly found that notifications are tricky things, especially in the context of building a general model. The diversity of what ...
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Should my application call statsd directly or should I call statsd based off logs?
I'm planning on incrementing counters in statsd based of various events within my application. I have logging in place for these events. So, from my viewpoint I have two options:
Update the ...
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633
views
Hierarchical ViewModels and tracking IsDirty/PropertyChanged events
I have a set of ViewModels depicted like in the below picture.
And, I have a couple of commands AcceptCommand, CancelCommand in the Top Level View Model that are bound to Apply, Cancel buttons ...
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ZeroMQ and Majordomo protocol
I am learning ZeroMQ and came across the Majordomo Protocol. I am wondering if I'm understanding this correctly, is the use case the same as.. for example.. the Microsoft Azure AppFabric service? ...
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532
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How can I put multiple hierarchical forms in a single web page and avoid making it a mess?
We are a group of developers working on a web application that accepts forms filled and sent by our users and present it in an overall view. Our main form view looks like this:
There are multiple ...
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Pattern for data types that are related yet fundamentally different in utility
Background
I'm currently working on a codebase for what is to become a forthcoming website's content "engine", where it will take in different types of standardized data (implemented with XML), parse ...
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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: ...
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Looking for design pattern to represent shared state in music sequencer
I like to give lots of context, but also to state the basic question up top as concisely as possible. Feel free to read a little or a lot.
I'm working on a music sequencer, and have been happy so far ...
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3
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1
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132
views
How to model workflows
I'm building a helpdesk-type system, where there are:
Customer - can submit/resubmit tickets;
Manager - can review submitted tickets, assign to developers (one ticket to multiple developers), review ...
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3
votes
1
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Message Mapper Design Considerations
Long question context, skip to tl;dr for the meat of it.
I am designing an integration between two web applications, and have come to the conclusion that a message pattern would be an appropriate ...
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1
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Best way to refactor service with too many dependencies
We are creating the backend for a web app using a sort of layered architecture. The service layer is supposed to handle the business logic and passing data to the repositories. This service layer is ...
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votes
2
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263
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Design of a modular application
I'm developing an application (Java) in a modular architecture. I have two approaches in mind and I'm not sure which one will be "better code" in case of maintenance and conventions.
I have ...
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votes
2
answers
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views
Design pattern to create a shared lib architecture
I am making a renderer as a hobby, one thing I thought to try is making the low levelAPI be dynamically swappable, i.e. you could have an opengl or vulkan backend and switch between the two without ...
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views
Is there an elegant way to handle run-time dependent object composition without using dynamic_cast?
Context
I'm attempting to design a modelling framework that is modular and easy to extend and test. (I'm trying to follow open/closed, dependency injection, and composition over inheritence principles)...
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Exposing methods for polymorphic children from the aggregate root
Consider the following fictitious toy example:
There is an aggregate root DayChecklist that holds a list of Tasks planned for the day:
class DayChecklist {
String id;
DateTime today;
...
...
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How to handle a bunch of nested ValueObjects?
I'm writing a PHP web application (or actually a Symfony module). One part of it is a nested structure of ValueObjects (meaning: they are immutable and have to be validated on the creating). Such an ...
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Is gRPC a good choice for my scenario?
Im starting to develop a visually-simple but infrastructural-ly robust real time multiplayer game to show off my backend skills and hopefully get a job at Blizzard or something like that.
The game is ...
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votes
2
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527
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destroy object once it won't be used anymore in flyweight pattern
I want to use flyweight pattern to return the same instance of my object each time.
public class ThingFactory {
private static final HashMap<UUID, Thing> things = new HashMap<>();
...
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Design Pattern to unify similar generated classes
I have a project where I work with generated classes for some web interfaces. Some of these classes are (almost) identical and most of the functionality I need them for only use the identical parts. ...
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Third-party API wrapper in Java: how to design
Suppose, there's a site that provides an API, such as this:
Users post questions, answers on that site
You can make GET and
POST calls
There are two types of authentication: weak (only gives
read ...
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