Скачать или смотреть Creating a Custom RxJs Operator with a Function Input

Learn how to create a custom RxJs operator that takes a function as input and flattens elements in an object effortlessly.
---
This video is based on the question https://stackoverflow.com/q/66302858/ asked by the user 'XRaycat' ( https://stackoverflow.com/u/7744154/ ) and on the answer https://stackoverflow.com/a/66304022/ provided by the user 'Mrk Sef' ( https://stackoverflow.com/u/13500986/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: RxJs custom operator with function as input

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding Custom RxJs Operators

RxJs is a powerful library for reactive programming in JavaScript, often used with Angular and TypeScript. One of its strengths is the ability to create custom operators that can transform and manipulate data streams. In this guide, we will delve into the process of creating a custom RxJs operator that takes a function as input to simplify the way we handle streams of data in an expressive manner.

The Problem

You may find yourself in a situation where you want to create an operator that combines multiple actions seamlessly. For example, if you have an observable containing objects and you want to flatten an array of properties within those objects, it can be cumbersome to chain multiple operators together like map and concatMap. The goal is to create a reusable operator that takes a function as its input, allowing for easier data transformations.

The Example Scenario

Consider the following TypeScript interfaces:

[[See Video to Reveal this Text or Code Snippet]]

Imagine you have the following observable:

[[See Video to Reveal this Text or Code Snippet]]

You want to achieve the following transformation: using a custom operator, you want to flatten the elements in the array of objects, so that the output looks like this:

[[See Video to Reveal this Text or Code Snippet]]

The Expected Solution

Instead of using both map and concatMap like so:

[[See Video to Reveal this Text or Code Snippet]]

You desire a cleaner approach such as:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

Understanding the Existing Operators

Before we implement a custom operator, it's important to note that there is already a built-in operator in RxJs called concatMap. This operator can actually cover the functionality we are attempting to create. The expression pipe(map(somefunc), concatMap(x => x)) is equivalent to concatMap(somefunc), which shows how the operators can simplify our code.

Creating the Custom Operator

To create your custom operator, you can redefine your function as follows:

[[See Video to Reveal this Text or Code Snippet]]

However, observe that this can further be simplified to:

[[See Video to Reveal this Text or Code Snippet]]

Important Considerations

Type Transformation: When creating the many operator, think about type transformation. Your operator is intended to change a stream of type T into something usable (Observable<R>), but concatMap requires a function of type (input: T) => Observable<R>.

Subscription Limitations: The concatMap operator cannot subscribe to boolean values. It needs to operate on observable values; thus, ensure your custom operator’s predicate returns an observable.

Conclusion

Creating a custom RxJs operator that handles function input is manageable with the right understanding of existing operators like concatMap. By following the guidance above, you can define your own operator that simplifies and streamlines your data processing effectively. Remember to always verify the type transformations and the expected outputs when composing operators to avoid subscription errors.

By utilizing RxJs efficiently, you can enhance your reactive programming experience, making your code cleaner and easier to read while leveraging the power of functional programming concepts.

If you're interested in further enhancing your skills in using RxJs, stay tuned for more tips and tricks in future posts!