Скачать или смотреть How to Pass Observable @ Input to Angular Component Store

Discover how to effectively pass `Observable` arrays to Angular components and manage state with the component store. Learn the essential steps and common pitfalls to avoid.
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How to Pass Observable @ Input to Angular Component Store: A Step-by-Step Guide

When developing Angular applications, you might encounter situations where you need to pass an Observable array into a child or inner component for further processing. This is particularly useful when you are working with a component store and want to display data dynamically. However, challenges may arise, especially if the data does not seem to load correctly. In this guide, we will explore how to properly pass an Observable to a component store in Angular.

The Problem

Let's set the stage with a specific scenario. You have an outer component that provides an Observable of sales history records. You want to pass this data to an inner component, where it can be filtered or mapped, and eventually used in some custom table rendering logic. Here’s what your setup looks like:

You are using the async pipe to pass the salesHistory$ observable to a child component.

You're updating the inner component's store based on the incoming data array.

Despite this, the sales history data does not load correctly during the first opening of a dialog component.

The Setup

Here’s a quick overview of how your outer and inner components are structured:

Outer Component

You are using the async pipe to bind the observable to the child component's input:

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

Inner Component

Your inner component has a setter for the salesHistory input that updates the store:

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

Component Store

Your component store is defined with the following structure:

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

The Solution

After analyzing the code, the main issue was with how the observables were being selected and processed, leading to data not being emitted correctly. Below is the corrected implementation that ensures the inner component receives the Observable properly.

Correct Observable Implementation

You need to modify how you select salesHistoryWithWhColors$. It is essential to ensure that you filter and map the observable correctly. Here is the improved code snippet:

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

How This Works

Select: We start by selecting the salesHistory state, which is an array of SalesHistoryLine.

Filter: We apply a filter operation to ensure that we only work with non-empty values.

Map: Finally, we map each sales history line to include the color information associated with the warehouse ID.

Conclusion

Passing an Observable to an Angular component via @ Input can seem daunting, but once you understand the underlying principles of how observables work within Angular’s reactive programming model, it becomes much more manageable.

Make sure to follow the right selection methods and observe how changes propagate through your application. By applying the corrected setup, you should now be able to display your sales history data smoothly, without facing issues on the first render. Happy coding!