Скачать или смотреть How to Convert Custom Objects to JSON and Back in Dart

Discover how to effectively convert custom objects, including nested lists of objects, to and from JSON in Dart. This step-by-step guide is perfect for beginners!
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How to Convert Custom Objects to JSON and Back in Dart: A Comprehensive Guide

When building applications, especially on platforms like Flutter, storing user data efficiently is essential. One effective method for doing this is by converting custom objects to JSON, allowing for easy storage and retrieval, such as in shared preferences. In this guide, we will walk through how to convert a list of custom objects within a parent object to and from JSON, specifically using Dart.

The Problem: Nested Custom Objects

Imagine you have an app where users can input various types of objects. In this case, we are focusing on a parent object called Resolution, which contains multiple properties such as:

Strings

Dates

Colors

A list of another custom object called Commitment

The main challenge arises when you need to handle the Commitment list within the Resolution object accurately. Simply converting the entire list to a string and back isn't sufficient; you need to manage the individual properties of each Commitment object effectively.

Let's break down the solution to this issue by outlining how to approach both the conversion to JSON and the reverse process.

Step-by-Step Solution

1. Define Your Custom Objects

First, ensure your custom classes are set up correctly. In our example, we have two classes: Resolution and Commitment.

The Resolution Class

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

The Commitment Class

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

2. Convert Resolution to JSON

The Resolution class needs a method to convert it into a JSON-friendly format. You can achieve this with a toJson method, which should also handle the nested Commitment list.

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

3. Convert Commitments to JSON

Since Commitment is a nested object within Resolution, we need a method to handle its conversion as well.

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

4. Convert JSON Back to Resolution

When retrieving data from JSON, you will need to convert it back into the Resolution object. The fromJson method can be set up similar to toJson.

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

5. Convert JSON Back to Commitments

The most crucial part is the conversion of the JSON array back into a list of Commitment objects. Here’s a corrected method to achieve that:

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

This method iterates through each item in the list, converts it back to a Commitment object using the fromJson method, and adds it to the commitmentsList.

Conclusion

Converting custom objects to and from JSON in Dart might seem daunting, especially when dealing with nested objects. However, by following these structured steps and utilizing the appropriate methods in your classes, you can simplify the process significantly.

Feel free to tweak the code according to your specific requirements, and don’t hesitate to seek help from the community when you hit a roadblock. Happy coding!