Resolving the Empty String Issue for Class Variables in Unity Prefabs

Learn how to effectively manage class variables in Unity when instantiating prefabs to avoid issues with empty string data.
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This video is based on the question https://stackoverflow.com/q/70052830/ asked by the user 'vrivon' ( https://stackoverflow.com/u/1703127/ ) and on the answer https://stackoverflow.com/a/70056925/ provided by the user 'Ruzihm' ( https://stackoverflow.com/u/1092820/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving the Empty String Issue for Class Variables in Unity Prefabs

When developing games in Unity, you might encounter scenarios where your class variables do not seem to retain their values. This can be particularly frustrating when working with prefabs and MonoBehaviour scripts. A common situation developers face involves class variables showing no data after instantiation. In this guide, we'll explore a specific example of this issue and provide a comprehensive solution.

The Problem: Empty Class Variable After Instantiation

Imagine you have created a MonoBehaviour script named Window, which contains a public string variable called request. You expect this variable to be set with a value during the object's lifecycle, however, upon instantiation, you find that it remains empty. Here’s a quick breakdown of what’s happening:

You are asynchronously loading a prefab using the Addressables system in Unity.

The Window class is set up correctly to initialize the request variable in the Awake method.

However, when trying to retrieve the request variable after instantiation, it results in an empty string.

Code Example

Here’s the Window class definition for context:

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

And the code snippet for loading the prefab:

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

The main issue here arises from trying to access the request value from the wrong instance of the Window class.

The Solution: Access the Correct Instance

The key to resolving this problem lies in correctly referencing the instantiated object instead of the prefab. In this case, the Awake function that initializes the request variable is called on the instance created by the InstantiateAsync method, not the one returned by LoadAssetAsync. To get the correct request value, you should modify your code as follows:

Updated Code Snippet

Modify your instantiation logic to ensure you are accessing the right instance like this:

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

Explanation

Async Instantiation: We listen for the completion of InstantiateAsync using a callback. This ensures that we interact with the fully instantiated game object rather than the original prefab.

Reference: By accessing op.Result.GetComponent<Window>(), you are now targeting the instance of Window that was just instantiated, allowing you to retrieve the initialized request variable correctly.

Conclusion

This common pitfall serves as a reminder of the importance of understanding how object instantiation works in Unity, particularly when using the Addressables system. By ensuring you are working with the correctly instantiated object, you can effectively manage your class variables and prevent unexpected behavior in your games.

If you’ve encountered similar issues or have additional insights, feel free to share in the comments below! Happy coding!