Unlock the Power of RxJS Subjects in Your Angular Projects
RxJS, a framework for reactive programming, has revolutionized the way we write asynchronous code. At its core, RxJS uses observables, making it easy to handle reactivity in Angular applications. But what about RxJS subjects? In this article, we’ll dive into the world of subjects, exploring their importance, syntax, and variants, and demonstrate how to use them in your Angular projects.
Getting Started
To follow along, ensure you have the following prerequisites:
- Node version 11.0 installed on your machine
- Node Package Manager version 6.7 (usually ships with Node installation)
- Angular CLI version 7.0
- The latest version of Angular (version 7)
Confirm your Angular version using the command ng --version, and update to version 7 if necessary. Download the starter project and initialize the Node modules in your terminal using the command npm install.
What are RxJS Subjects?
RxJS subjects are observables that also act as observers, providing a platform for data values to be multicasted to multiple observers. Unlike regular observables, which can only handle one observer, subjects can handle multiple observers, making them a powerful tool for handling reactivity in Angular applications.
Why are RxJS Subjects Important?
Subjects offer several advantages over regular observables. They can multicast data values to multiple observers, making them ideal for scenarios where multiple subscriptions need to receive different data values. Additionally, subjects can act as both producers and consumers, shifting the reach of observables from unicast to multicast.
RxJS Subject Syntax
In an Angular project, defining an RxJS subject is straightforward. The syntax looks like this:
Demo: Multicasting with RxJS Subjects
Let’s illustrate RxJS subjects with a few examples of multicasting. Open your app.component.ts file and copy the code below into it:
You’ll see that, unlike observables, subjects don’t require a helper module to create them. With a simple new Subject() construct, you can use it just like any observable.
Working with Multiple Observers
One of the main features of subjects is their ability to have multiple observers set that can reference it. Let’s see this in action with the same logic as before. Copy the code block below into the app.component.ts file:
If you save the file and recompile, you’ll notice that although there are two observers for the subject, the various observers still return data values as expected.
Subject Variants
RxJS offers three variants of subjects:
Behavior Subject
The behavior subject is a special type of subject that temporarily stores the current data value of any observer declared before it. Let’s illustrate this with an example:
Replay Subject
The replay subject is similar to the behavior subject but allows you to store more than the current value. You can specify how many values you want to emit from the last observer. Here’s an example:
Async Subject
The async subject acts exactly like the behavior subject but can only execute after a complete method is called. Let’s see an example:
Conclusion
In this article, we’ve explored the world of RxJS subjects, covering their importance, syntax, and variants. With this knowledge, you can now start using subjects in your Angular projects to handle reactivity with ease. Happy hacking!