Скачать или смотреть Resolving Unhandled Exception: type 'int' is not a subtype of type 'String' in Your Flutter App

Discover how to fix the `Unhandled Exception: type 'int' is not a subtype of type 'String'` error in your Flutter app when working with APIs. Learn step-by-step how to adjust your model for successful data retrieval!
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This video is based on the question https://stackoverflow.com/q/64447560/ asked by the user 'Furkan Demirel' ( https://stackoverflow.com/u/10764674/ ) and on the answer https://stackoverflow.com/a/64447753/ provided by the user 'M Alkhatib' ( https://stackoverflow.com/u/11703061/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Error: Unhandled Exception: type 'int' is not a subtype of type 'String'

If you're developing a Flutter application that interacts with APIs, you may encounter the dreaded error: Unhandled Exception: type 'int' is not a subtype of type 'String'. This issue stems from mismatches between data types in your model and the data returned by the API.

In the example at hand, the error occurred when trying to parse a JSON response into a Dart model. Let's break down the problem and provide you with a clear solution.

The Problem

You have defined a model in Dart that looks like this:

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

Here, the field sinifID is mistakenly defined as a String, while the API is returning this value as an int. Hence, when the app attempts to create a DerslikListesiModel instance using this data, it fails due to a type mismatch.

The Quick Fix

To rectify this issue, you need to adjust the type of sinifID in your model. Here’s how to do it step by step:

Step 1: Change the Data Type

Open your DerslikListesiModel.dart file and modify the sinifID field's type from String to int:

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

Step 2: Test Your Changes

After making this change, run your application again. The error should be resolved, and you’ll be able to see the data displayed on your screen without any exceptions.

Additional Considerations

Always ensure that your model reflects the data structure of the API correctly, especially when dealing with types like String, int, bool, etc.

Use null safety features in Dart (if available) to avoid potential null-related issues.

Conclusion

In summary, the Unhandled Exception: type 'int' is not a subtype of type 'String' error arises from type mismatches in your Dart models when interacting with JSON data. By adjusting the sinifID field from a String to an int, you align your model with the data being returned by the API, effectively resolving this issue.

Happy Coding!

Feel free to leave a comment or share your experiences with handling APIs in Flutter – we’d love to hear from you!