Questions tagged [observer-pattern]

A software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods.

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Dependency problem with field changes

The Observer Pattern is used here to notify changes in a Person's data. For example, when age changes, the value of can_vote() ...
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Generic observable type

I am writing an observer design pattern that is not too complex but I still feel there's a lot for me to learn about C++ be it little details (especially coming from C). A couple of observations: I ...
xyf's user avatar
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PyGame Event Handling

I'm new to pygame and tried to write my own Event Manager because I couldn't find a solution I was satisfied with. So I wrote my own inspired by the observer pattern: ...
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Multithreaded observer pattern in Rust

I often want to program in an event driven way, but classic implementations of the observer pattern often pose an ownership challenge, and they only get more difficult once multiple threads are ...
Blue7's user avatar
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2 answers
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Requests and handling requests

For this task, I don't think that the Observer Pattern can be used in its classic form. Those who have received the requests and those who choose to accept the request are not the same group. Those ...
prestokeys's user avatar
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Typescript simple observable state and web component

I've been experimenting with wiring up a vanilla web component in a reactive manner to a state box. The goal is that when something changes on the state object, the web component reacts. I realize ...
Jeff Putz's user avatar
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3 answers
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Observer Design Pattern in C++ to model magazine subscriptions

My attempt at a observer design pattern (I know using namespace std isn't good). I'm very new to design patterns. Everything is inline with class definition. Please tell me if I'm doing anything wrong ...
Asphodel's user avatar
3 votes
2 answers
607 views

Generic Observer/Listener implementation in Java

I am working on a personal project in university where I am currently trying to make my own implementation of a generic observer pattern that I can use throughout my project. I would appreciate any ...
Emil Holmsten's user avatar
3 votes
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281 views

Android BMI calculator using LiveData

I have made a Body mass index-calculator using ViewModel and LiveData. Source-code of the MainActivity: ...
michael.zech's user avatar
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Unity3D Observable Variables as ScriptableObjects

I'm trying to implement an observable pattern on variables, so that I can hook up UI components, etc. to change displayed values or other actions when their value changes. I wanted three features that ...
Tom's user avatar
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2 answers
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C++ Observer Pattern with std::function

I am/we are using the observer pattern for many things in our application. I think it's time to create a reusable base class for these situations. Most implementations I could find only do something ...
Michael's user avatar
3 votes
1 answer
521 views

Adjusting variables on change of status attribute of my Order Laravel model on the updated event in observer

I have an order model and a client model. A client has many orders, an order belongs to a single client. In the client model I keep track of how much money a client paid (...
Bogdan Ta's user avatar
3 votes
1 answer
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Abstract wrapper for fundamental types

I have created this interface as part of my C++ learning path. This post inspired me a lot. The idea is to use its concrete implementations to perform some actions before and after any change of the ...
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Observer pattern in Rust

A simple implementation of the Observer pattern in rust. The Observable constructor (::new) is called with a subscription function which will be called every time ...
Luke Skywalker's user avatar
2 votes
1 answer
104 views

Pure JavaScript infinite scroll

I have a 4 list of posts. I am trying to load more posts (clones of the "original" ones) when I reach the bottom of the container. ...
Razvan Zamfir's user avatar
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1 answer
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Angular observables piping

I wanted to check and see if this was as efficient as can be. The goal is to get a user's data from a group of documents that contains references to users in Firestore. ngOnInit ...
Sree Grandhe's user avatar
3 votes
2 answers
962 views

A Python decorator for an "observable property", that notifies observers when the data is changed

I have classes that have some data, and whenever this data changes, it should notify observers of that data change. There also should be a method to add new observers. My first approach was to use a ...
Blue7's user avatar
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Create IObservable<T> From Func<T>

These extensions create an IObservable<T> that creates a long running task that can be cancelled. It runs the Func<T>...
Christian Findlay's user avatar
7 votes
1 answer
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JS stopwatch using the observer pattern

I'm learning OOP and also trying to learn and implement some design patterns. This question is a follow-up of Stopwatch interface OOP (Vanilla JS) The app is available in https://nacho-p5.github.io/ ...
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NativeScript - Angular Service to watch iOS keyboard event listeners

I'm writing an app with NativeScript 6.4.1 and Angular version 8. There are a series of UI events in iOS that you can watch to see what the keyboard is doing: https://developer.apple.com/...
user1261710's user avatar
3 votes
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Observer pattern over FFI

I'm trying to write up a cross-platform rust library (one, that will be used in iOS/Mac/Android dev etc.) It is based largely on concept's and code from Mozilla. One of the requirements I have is to ...
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Using generators on Observable class

I've decided to implement a simple case of the Observer pattern. I've gone about this considering you can only register 1 single observer in the Observable, instead of allowing multiple ones. I ...
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1 answer
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High-Level Managed Observers

I was thinking of adding a very high-level implementation of the event/observer pattern to my project. The implementation would manage adding and removing observers as "needed". You can use an almost ...
Nic.Star's user avatar
2 votes
1 answer
394 views

Notify observers when object attributes update

I have a Singleton manager class for managing request model and its attributes. My main aim is update object observers when some of the object attributes changes. ...
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Observer Design Pattern in Golang

I am trying to practice the Observer design pattern in Golang, here is my code. I would be pleased to receive your comments, improvements, etc. ...
Mazdak's user avatar
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3 votes
1 answer
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Logic is stored in Components that receive input data and update output data via Observables

I have C# ASP.Net Core Webapi application that makes some calculations for physical models. I have this project class: ...
rst's user avatar
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Implementing custom observable classes

I want to implement my own custom observable class so I can have a hierarchy of components and the closest defined configuration item bubbles to the front. ...
Adrian Brand's user avatar
1 vote
0 answers
13 views

RXJS and Ionic- Sequencial Subscriptions Waiting on User Action

In an Ionic App a user can open a new browser via "inAppBrowser". I'm trying to get the stats of the user before they go into to the inAppBrowser, get the stats again when browser closes, and then run ...
av0000's user avatar
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1 answer
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How to observe multiple Observables? [closed]

About the Program It's a simple implementation of Observer Pattern. The choice of different NotifyMethod will affect how those observers are notified. The ...
RainningTW's user avatar
4 votes
0 answers
120 views

Scheduler built with observables v3 (follow-up) - now testable

This is a 2nd follow-up to my previous one about a Scheduler built with observables. Although the last one was working correctly, it was only possible to see this ...
t3chb0t's user avatar
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1 vote
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Applying Observer-Observable pattern to a code and multithreading

I have to: 1) Apply the Observer-Observable pattern to the original code. 2) starting from the original code, I have to suppose that the modification of the array fields (slot machine numbers) ...
NoProg's user avatar
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2 votes
0 answers
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Observer(Event) system (Signals and Slots), type and template based

Signals are represented as types. You can connect a member function of some instance to the Observer system. This connected function will be called whenever a signal of a type that is the same type as ...
Darius Duesentrieb's user avatar
7 votes
1 answer
407 views

Threadsafe oneshot-event which fires on subscription if the event was fired in the past

Assumptions Basically, a Connection class has a "Disconnect" event. Subscribing to this event isn't thread-safe, because the disconnection may fire from another thread right before I subscribe. So ...
Oachkatzl's user avatar
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1 answer
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Apply stock quote changes using observer pattern

I am implementing observer pattern(refering codeproject) for stock quote update. I have created an interface for Subject and Observer. I have created instances for Subject and Observer and also the ...
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3 votes
1 answer
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Implementing the observer pattern for a stock exchange scenario

I am trying to implement the observer pattern for a stock exchange scenario. Multiple stocks can be registered at a stock exchange. There will be stock observers who are observing some specific stocks....
Mahesh Jagtap's user avatar
5 votes
1 answer
87 views

News reading application version 2

following the answer I got from t3chb0t last time News-reading application using the Observer pattern and also following the example here https://msdn.microsoft.com/en-us/library/dd990377(v=vs.110)....
Gilad's user avatar
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4 votes
1 answer
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Simple event dispatcher

Here is my very first event dispatcher. I would like to get both, style and code review, as well as some ideas to improve this implementation (new features etc.) I tried to write code in C++17 style ...
NutCracker's user avatar
3 votes
1 answer
2k views

Angular service for fetching and passing data with observables

I have an Angular service consisting of three methods: This method makes a call to my server to get a URL ...
Noah Hornak's user avatar
4 votes
2 answers
1k views

Make an Array Reactive (Observable)

I have written a simple JavaScript function to make an array reactive (i.e. observable). Is there anything I could improve? What the code does is take an array, a callback and a ...
Jacques Marais's user avatar
2 votes
1 answer
99 views

JavaScript and RxJS Password Strength Indicator

This is my first time using RxJS (or any observable library). It seems to work okay but I'm not sure about best practices. The thing that I am most unsure about is subscribing to the observable ...
Matthew Smith's user avatar
5 votes
1 answer
144 views

Scheduling using System.IObservable 2.0

As a follow up to this first attempt to create and use my own IObservable<T> implementation, this is version 2.0. The goal has been to correct the code where ...
user avatar
4 votes
1 answer
159 views

Scheduling using System.IObservable

With great inspiration from t3chb0ts ongoing work about scheduling, cron jobs etc. (last post here), I decided to make my own version of the Scheduler - using the observer pattern - as a learning ...
user avatar
7 votes
0 answers
250 views

Scheduler built with observables v2 (follow-up)

It would probably be too easy if the old Scheduler worked as intended being that simple. But an eye-openig review showed that from time to time it'll miss one ...
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5 votes
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Scheduler built with observables

I sometimes have to schedule some tasks and wanted to have my own reusable scheduler. Since I like the Rx, I build it on top of it. Follow-up There is a newer version of the ...
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6 votes
1 answer
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Java Pub Sub implementation using broker

I have developed a simple pubsub event subscription in java. Something similar to this thread Simple Pub-Sub Event Emitter These are the goals. Class should be able to "listen" to events happening ...
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2 answers
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JavaScript library to notify watchers of changes

Background Last year, while I was still entering the beginning of Immutability and Pure functions and whatnot I created a library for the community called ...
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2 votes
1 answer
533 views

Implementation of observer pattern for Node.js

I wrote an implementation of observer pattern as part of my online battle Chess game: ...
Furman's user avatar
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2 answers
2k views

Observable implementation

I have implemented a simple Observable class. I think that there is still room for improvement. Especially the fact that I have separate array to observe results ...
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4 votes
1 answer
2k views

Implementation of Observable with multiple callback function signatures

I have been playing around with ways of implementing a generic class for supporting the observer pattern. I have already asked to review a basic approach here. Now I have come up with an Observable ...
bone's user avatar
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5 votes
1 answer
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Implementation of Observer Pattern in C++14

I have written a small class for implementing the observer pattern in C++(14). I would welcome any comments, corrections criticisms and suggestions. Observable.h: ...
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