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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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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) ...
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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 ...
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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 ...
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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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1answer
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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....
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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)....
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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 ...
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1answer
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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 ...
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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 ...
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1answer
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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 ...
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1answer
93 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 ...
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1answer
79 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 ...
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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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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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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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Fetching student and teacher data from a given date range

I have two APIs which fetch data of teachers and students from a given date range. I am using forkJoin to get both APIresponse and display the data with a regular interval of 10 ms. This is working ...
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2answers
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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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Subscribing to multiple sources in RxJava

I have used RxJava to Observe multiple sources and then perform action depending upon values of Observables. I want to know if it can be further simplified. Goal: Complete implementation of RxJava. ...
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1answer
168 views

Implementation of observer pattern for Node.js

I wrote an implementation of observer pattern as part of my online battle Chess game: ...
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530 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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1answer
553 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 ...
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1answer
879 views

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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Observer pattern implementation in C++11

Can this observer pattern implementation be improved? Problem: User will drive a car if pressed l --> car move left c--> move middle ,r--> move right ...
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C++ implementation of the observer design pattern

Started learning design patterns using C++. Below is an implementation of the Observer Pattern. Two abstract class templates Observer and ...
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1answer
505 views

Angular - reusing an observable for different queries

This is just a dummy example, but in my real world application I get a lot of data from the web API and I'd like to manipulate it on the client's side. So, I kind of stored the observable I get from ...
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Observable Logger

I'm experimenting with an alternative abstraction layer for logging that is build on top of the Reactive Extensions. This allows me to easily add features I need to my layer and map logs to any other ...
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Retry and CircutBreaker the reactive way

I wrote a simple utility for Retry and CircuitBreaker patterns. I implemented it by using ReactiveX because I thought it might actually be the perfect framework for it. I know that there is a project ...
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1answer
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Store first value of http request with rxjs but keep doing httprequest

With RXJS library : I need to store values from the FIRST http request, but keep doing other http request on demand. I have done this code so far, and that is working. But I think there is a more ...
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Simple chat client and server in Java. (tried to refactor on Head First Java code example)

In the book Head First Java there was this coding example that created a very simple chat client and server. Both the server and the client consisted of just one class. I left the server code as is, ...
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Network of senders and receivers in C++

I am trying to create a Sender-Receiver Network. What do I mean under a Sender-Receiver Network. That means that there is some structure which consists of Nodes and connections between them which will ...
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662 views

Angular2/4 broadcast service using RxJS

I am no expert in RxJS as I am still learning my way around the new paradigm of Observable/Subject. I was trying to implement a broadcast service (based on NgRadio) that allows a new subscriber to ...
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Lightweight flexible observer framework using weak references

I found a need for a simple, generic publish-subscribe framework for my Java application. I looked over a few implementations on Code Review and I think mine avoids most of the pitfalls. Single-...
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F# Observable.subscribeWeakly implementation

In this SO question I needed an observable subscription function that can be used kind of like Observable.subscribe, but that does not keep a strong reference to ...
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Observable Object

I have created an observer and an observable object class. The idea being that you can create an observer that does some action whenever object being observed changes value. Design goals: Be able ...
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1answer
246 views

Merging union Observables

I am having a scenario where I need to execute observables that depends on the result of the first one. However I need to keep the result of the first observable. I couldn't find any extension that ...
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240 views

Simple C++11 Subject-Observer

Building on the answer in C++ class member callback simple examples, I've tried to put together a simple subject-observer pattern without needing to inherit a virtual Observer class. I also wanted to ...
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1answer
374 views

Observer pattern for temperature and pressure sensors

I have tried to implement the observer pattern. The code should be able to handle a variable number of observables (set compile time) and notify any number of observers/registerables. Any observable ...
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1answer
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Angular 2 clock with RxJS Observable

I'm fairly new to Angular 2 and I started off with creating a clock for my app. I tried to stick to the official documentation tutorial. Folder structure: The CSS file is still empty and the HTML is ...
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Observer pattern using a set of observers and delegated properties

The idea is to implement the observer pattern, with a separate notification method for each observed property of the observed object. Let me start with a simplified use case: ...
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2answers
336 views

Reusable Implementation of the Publish-Subscribe Pattern

I've finished an implementation of what I believe the Publish-Subscribe pattern is for practice and possible use in personal projects even though this implementation is fairly similar to the Observer/...
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1answer
427 views

WPF async ObservableTaskQueue class

I'm currently working on a WPF application, making calls to various web APIs. Thus, I'm looking after a special observable tasks queue: Progress value must be available Tasks (API calls)/seconds must ...
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1answer
103 views

Removing same event from listener

I have a myDiv.mousedown, window.mousemove, and window.mouseup event. I'm trying to organize ...
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2answers
172 views

Brightness adjustment control for multiple UI elements

I have an application that basically exists as a map and some controls. The controls change the look and feel of the map. I have a slider which is used to change the brightness, for example. At the ...
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2answers
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TextBoxes for various number types

Is there a way I could somehow have all this classes condensed into one, while keeping the code as clean as possible? They are all doing essentially the same thing, just for the different number type....
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1answer
99 views

Using a new thread to post to observers

I have implemented my own Observer pattern. I want to post my events in a new thread. This thread would simply call all the the observers/listeners with the posted event. ...
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332 views

Rust publish/subscribe channel library

I've written a simple multiple-sender multiple-receiver channel, but I'm unsure if my approach is the best way to do this. I'm not using multi-threaded primitives but instead wrapping around std's ...
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1answer
171 views

WindMIll Data Publisher using observer pattern

Problem statement : There is a windmill which collects and stores wind data for various cities. The data is maintained in an xml file by the aggregator part of windmill. Now I am trying to implement ...
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1answer
1k views

Simple event manager in Java

I have created a simple event manager and I want it to work properly in a multithreaded environment: ...
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539 views

JSON Data Observer

I wrote a small piece of code for observing changes on JSON object. Whenever there is a change in Object, it should trigger all the handlers with simplistic information about data change. I am ...
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Pattern observer

This is my dispath events code: ...