Скачать или смотреть How to Observe Field Variables of Another Class in MobX Flutter

Learn how to effectively observe field variables of a different class in MobX Flutter, ensuring seamless state management in your applications.
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Observing Field Variables of Another Class in MobX Flutter

When working with state management in Flutter, particularly using MobX, you might encounter the need to observe changes in a variable from a different class. In this guide, we will explore how to observe a field variable from another class in a MobX store. This guide will help you navigate through MobX’s features to create responsive and reactive applications.

The Challenge

You may have a class, for example, A, that has an integer field x. The goal is to observe changes to x from another MobX store class, MyStore. Initially, it might seem straightforward to use the @ observable annotation, but you may find that it doesn't work as expected outside of a MobX store. Let’s take a closer look at how to implement this correctly.

Sample Class Definition

Here's an overview of the initial class setup:

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The Solution

To effectively observe changes to x within class A, we need to make a few modifications. The core concept here is to employ MobX's Observable class rather than just relying on the @ observable annotation. Here's how to do it:

Step 1: Modify Class A

Instead of using a normal integer for x, utilize the Observable class. Here's an updated version of class A:

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

This change defines x as an observable variable, allowing it to notify observers whenever its value changes.

Step 2: Update Your Store

Next, adjust the MyStore class to accommodate the observation of a.x. Here’s how that can look:

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

In this modification, take note of the following:

The @ observable annotation is removed from a since a.x is what's being observed.

A computed property xSquare is introduced, which recalculates its value whenever a.x changes. This makes your store responsive to changes in x.

Key Takeaways

Use Observable: Instead of the standard integer type for properties you want to observe, utilize MobX's Observable class.

Computed Properties: They allow you to derive and react to changes seamlessly without directly observing every single variable in your store.

Accessing Values: Remember that when using Observable, you need to access the actual value using .value.

This guide should provide you with a solid understanding of how to observe field variables in a different class using MobX. With these techniques, your state management will be robust and reactive to changes in your Flutter application.

By following these methods, you can ensure that your application reacts accurately to changes in state, leading to a seamless user experience.