How to Successfully Use JsonUtility.FromJson for JSON Deserialization in Unity

A comprehensive guide on using JsonUtility.FromJson in Unity for deserializing JSON data, including common mistakes and structured solutions.
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This video is based on the question https://stackoverflow.com/q/68504652/ asked by the user 'Suleiman Almaawali' ( https://stackoverflow.com/u/8512148/ ) and on the answer https://stackoverflow.com/a/68504957/ provided by the user 'Blogy Junky' ( https://stackoverflow.com/u/14995838/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Deserializing JSON in Unity with JsonUtility

Working with JSON data can be challenging, particularly when you are trying to serialize or deserialize objects in Unity. If you have run into problems while attempting to read a JSON string in Unity, you are not alone. Many developers face challenges when using Unity's JsonUtility.FromJson method for deserialization. In this post, we will walk through a common issue, identify the mistakes, and provide clear solutions with examples to help you deserialize JSON data efficiently.

The Problem

A user posted an issue regarding deserializing a JSON string. They created classes based on the JSON response they were receiving, but could not successfully deserialize the JSON. Let’s take a look at the JSON structure they provided:

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

The Classes

Here's a quick look at the classes the user originally created to represent this structure:

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

They attempted to deserialize the JSON using this line of code:

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

However, they encountered problems.

Common Mistakes and Solutions

1. Correct Usage of Attributes

The first thing to note is the correct usage of the [System.Serializable] attribute. In Unity, you must use this attribute correctly for your classes to be deserialized properly. You should replace [SerializeField] with public fields directly.

Solution:

Remove [SerializeField] and make the fields public.

Use [System.Serializable] only.

2. Correct Property Names

When it comes to deserialization, the property names in your class must directly map to the keys in your JSON. The Response class should not have the property public List<Result> result { get; set; } since that will not properly map to the "response" part of your JSON.

Solution:

Rename result to response (it should be an object, not a list) and create a new class to encapsulate the list:

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

3. Constructors for Class Initialization

Another essential aspect is the presence of constructors in your classes. Although Unity's serialization might not require explicit constructors for functionality, it might help in ensuring that all properties are initialized correctly.

Solution:

Add default constructors as demonstrated in the above classes or use properties directly.

Final Implementation

Here’s how the final implementation would look:

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

With the corrected definitions in place, you should now be able to deserialize your JSON successfully:

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

Conclusion

Deserializing JSON data in Unity using JsonUtility.FromJson can be straightforward if you follow the essential principles regarding class structure and member visibility. By ensuring that your classes correspond accurately with the JSON structure, you can easily convert JSON strings into usable Unity objects. With these tips, you’ll be better prepared to handle JSON deserialization in your projects. Happy coding!