Questions tagged [event-programming]

Event-driven programming refers to the programming technique where the flow of the program is driven by recognition and handling of events such as mouse clicks, key presses, etc.

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How can I avoid both objects A and B using class C (or is it unavoidable)?

I have the following setup: An object A running as a separate service with its own address (implemented via Pyro package in Python). An object B running as a separate service with its own address. ...
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1answer
2k views

Handling events and incoming Web API calls simultaneously

I'm working on a project where I got an architecture with multiple "Microservices" communicating with each other by using an event bus (RabbitMQ). I got an Web API-project set up for each service so ...
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1answer
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Is it a bad practice to subscribe to an event with an Action

I use a third party library for speech recognition. This library give me access to some classes ( SpeechRecognitionEngine, SpeechRecognitionConfiguration etc) which give me access to some events (...
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2answers
349 views

Is a promise-aware eventing system desirable?

I'm fully aware that Promises and eventing are both ways to do asynchronous programming, and you can choose either one for a given project. However, in practice, the code base I'm working with is ...
6
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1answer
371 views

How to trigger other events in MVC, once the desired event completes?

What is a technique in MVC that can be used to trigger updates? Namely, When user clicks a button save a product I have this: function saveProduct($product) { $this->repository->...
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6answers
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How to create a timed-event architecture using a SQL database

The title of my question is general because I feel like this problem is of a general nature, but to set the stage I'm going to provide a specific example. We use a homegrown workflow engine that is ...
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2answers
66 views

Proper event driven design when a consumer subscribes to many producers

I have a large number of instances of a class. Those instances can fire an event. The only important thing for that event is which instance fired it. I have another instance of a class (and maybe in ...
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0answers
114 views

Sending events down a tunnel, and bubbling them back up

I am working on developing an HTML canvas application, where I need to be able to do my own UI event processing. That's where the stem of this question comes from, but I'd really like to understand ...
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1answer
289 views

How would you structure a flowchart/data flow diagram for an application that runs on a game engine?

I understand how you create flowcharts or data flow diagrams for simple linear based programming. But how do you design a flowchart for event based programming, like a game that runs on Unity3D? How ...
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1answer
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Should I use a command or an event?

The difference between a command and an event in bus communication seems a little vague to me. I know that commands should be executed once only, while an event can be handled multiple times, but ...
6
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1answer
1k views

Can event emitters be functional?

For instance, array.map accepts a callback that returns a value. const newArray = oldArray.map(item => doSomethingTo(item)); Promises also accept callbacks that return a value. const ...
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1answer
92 views

Pattern matching events with arbitrary structure

My team implemented an alert broker system. The way it works is this: Event sources generate events, with mostly arbitrary structure, and the broker listens to them. Users go to the broker and use an ...
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1answer
145 views

What pattern should I set for handling event as working item?

I have this business event : "CustomerUpdated" published by my system. I have many application listening to these events, and they do all king of action : sending email, updating the database, ...
2
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1answer
98 views

ADO.NET - Is it better to handle a combo box or label event, and where should the data be sourced from?

Context I recently wrote a final exam that required using a BindingSource object with ADO.NET to populate a number of combo box and label controls from which the user could perform basic business ...
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8answers
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Are events only used for GUI programming?

Are events only used for GUI programming? How do you handle in normal backend programming when something happens to this other thing?
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1answer
168 views

“An event can be made of two parts, the event header and the event body.” Is this about event or event notification?

From: https://en.wikipedia.org/wiki/Event-driven_architecture Considering: Events do not travel, they just occur. Are the following statements valid? Event channels are conduits in which events ...
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1answer
112 views

How to prevent endles event recursion when using event driven data view?

Consider that you have some graphical interface that represents some data structure. For example a text field: This field is connected to the data structure through events. I tried to make diagram of ...
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2answers
1k views

In an event driven microservice environment, are domain events equal to topics?

A lot of messaging frameworks have the term "topic". In a ddd microservice architecture, do these topics always reflect the domain events?
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4answers
2k views

Callbacks without concurrency? [closed]

To sync on the terms I will first give my perspective on what a callback function in the simplest possible terms: A callback function is a function that is executed as a response to a certain ...
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2answers
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Event driven programming in Haskell

I'm new to Haskell, so this is more a high-level conceptual question. I've read this: https://wiki.haskell.org/Real_World_Applications/Event_Driven_Applications and it has this: run :: Domain -> [...
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2answers
836 views

Ensure that callbacks registration and triggering don't cause infinite recursion

I just spent a long, miserable week debugging a stack-overflow in a C++/Qt application. The fundamental problem was that I had a function that accepted a callback, and in certain cases the callback ...
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3answers
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Use case for async/await?

Background Most of the applications that I write are hour long sequential tests for electronic equipment. The equipment under test has a specification that is a state-machine that looks like... Get ...
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2answers
341 views

Eventing solutions for Java legacy applications too old for real JMS queue/topic eventing?

What are some architectural solutions that can mimic eventing for systems (Java) that are too old to implement eventing solutions, such as conventional Queue/Topic based JMS messaging? I have a ...
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4answers
3k views

Event-driven programming: when is it worth it?

Ok, I know the title of this question is almost identical to When should I use event based programming? but the answers of said question have not helped me in deciding whether I should use events in ...
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1answer
193 views

For Web front end, if there are 20 JavaScript files loading, how to track down the mouseover handler?

For Web front end programming, since any JavaScript can set up an event listener for "mouseover" or "mouseenter" for an element, if we are to track down what is the code that is responsible for making ...
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0answers
356 views

Using events and event subscribers to create windows in a desktop application

I should probably open this by saying I do mostly Web applications at work, which obviously have some major differences from typical desktop stuff. I had a small Windows Forms program I'd made for ...
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1answer
137 views

"Who" should handle side tasks for events?

I'm currently on the process of creating a website/webapp. My application is based on Node JS with the express framework. My core backend concept consists of routers: handle http request. Like [...
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1answer
840 views

Why does Node not support several event loops in one Process?

As the title says, why does Node not support several event loops in one Process? The idea, is that node spawns a user decided number of threads, which each have an event loop. When a new callback is ...
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2answers
102 views

What is the name for user-defined methods / functions that get called implicitly? [closed]

I want to mark such methods in my application code with a comment that highlights that these methods are expected to get called by the framework / compiler the application is written for, even if the ...
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4answers
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Why use plus equals += for event registration?

In C#, you register an event like: window.onClick += myHandler; But why use this instead of a "register" method that takes your handler and registers it. E.g.: window.registerOnClick(myHandler); ...
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0answers
131 views

Sharing identical events, with differing scopes, between client and server libraries, in a micro-service architecture

I have a shared user repository (id, name, e-mail, password, etc.) exposed as a REST service - and multiple independent websites accessing this REST service (from the back-end) as a means of sharing a ...
9
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1answer
790 views

Is event sourcing only for when writes are rare?

I'm reading up on event sourcing and can't stop asking myself if it only makes sense in exotic situations where writes are very rare or military-grade auditing is required. A non-exceptional system ...
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2answers
1k views

Persistence models for Event Sourcing

I am intrigued by the Event Sourcing pattern but am struggling to design an event sourcing model and put it in concrete form. First off, I want to make sure that I understand the main use cases of ...
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1answer
261 views

Object Communication Design

Multiple top-level systems that communicate with each other via messages(events/commands). The Main class of the program wraps around all the systems and has a message dispacher component wich ...
4
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1answer
479 views

Identity propagation using Azure service bus

We currently have a platform with a SOA architecture in which the user's identity is propagated from the web application via middle tier services (REST and SOAP) until we actually query our data ...
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0answers
231 views

Web framework architecture with non-blocking I/O

There's been a lot of news in the enterprise world lately, specially in the web, and I've decided to build a small web framework on top of Netty to learn more about asynchronous programming and event-...
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2answers
5k views

What's the simplest way to deal with events in C in this situation?

I'm writing a text-based game, in C. I want the game to handle NPCs movement and actions in the background, while the user is making his moves. I'd also use time-based events to tell the user when ...
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3answers
2k views

When is a event listener invoked during program execution?

I am using the Obervable-Observer Pattern. MyClass extends Observable{ invokeListeners(){ doSomething; setChanged(); notifyListeners();//This invokes onUpdate() in "implements ...
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3answers
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Are imperative events an anti-pattern?

Are events which are intended to tell listeners to carry out explicit actions an anti-pattern? Imagine a worker service which raises the event WorkStarted at its beginning and the event WorkFinised ...
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1answer
17k views

Should I use: One event multiple subscribers or multiple events multiple subscribers

I am writing a data acquisition application. I wondering whether I should use one event multiple subscribers or multiple events multiple subscribers. I am worried about performance. Also could I ...
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2answers
159 views

Receive events in an event-loop, single-threaded

Let's say I have a program which consists of a main event loop. The event loop should check for tasks and if one exists, it is to be processed. The user interface consists of a GUI with buttons, for ...
3
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1answer
238 views

Structure project based on platform or design?

I have a medium sized project (~10,000 lines) that runs on Windows and Linux. However it is only specific components of the program that are platform dependent and are located in a folder called ...
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2answers
1k views

Observer pattern without state change?

My question is whether there is a similar pattern to Observer that does not imply a state change in the observed object. The following is a concrete example: I have a ConnectionFactory class which is ...
2
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1answer
131 views

What are the underlying patterns in systems allowing asynchronous operations?

Say I'm working with a system that allows async, nonblocking operations. If I queue up a set of those operations and specify their result buffer references: nonblocking_write( message, write_buffer )...
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1answer
191 views

Event action abstraction and trigger control

I am thinking of abstracting Event action in order to make further alteration/implementation/maintenance easy since the project I am currently working on has volatile requirement. So I thought of the ...
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6answers
3k views

How to handle initial state in an event-driven architecture?

In an event-driven architecture each component only acts when an event is sent through the system. Imagine a hypothetical car with a brake pedal and a brake light. The brake light turns on when it ...
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1answer
2k views

Why do browsers clamp timeouts and intervals?

I've been working on some abstractions of setTimeout and setInterval in order to process large sets of data without blocking the event loop in the browser. Upon this, I have discovered that browsers "...
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1answer
1k views

Are there any design pattern to data binding in event driven architecture?

I develop a browser based game with node.js in back and HTML5 canvas in front-end. It use WebSockets for communication. My plan is to generate business events in client side, e.g.: "finishJob". ...
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5answers
27k views

When should I use event-based programming?

I have been passing callbacks or just triggering the functions from other function in my programs to make things happen once tasks complete. When something finishes, I trigger the function directly: ...
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3answers
548 views

Event Driven Objects/Framework on the Web [closed]

I am a desktop developer moving to web development. The guys who I am working with use procedural PHP, and coming from an event driven, objectified perspective (using WPF and C#.Net) I am completely ...