Resolving the Flutter Error: '_Map String, dynamic ' is not a subtype of type 'List dynamic '

Discover how to fix the Flutter error you encounter when your API responds with a JSON object, but you treat it as a list. Learn the right approach to handle API responses in your Flutter apps.
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Troubleshooting Flutter Error: '_Map<String, dynamic>' is not a subtype of type 'List<dynamic>'

When developing Flutter applications, encountering errors is a common experience. One such error is:

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

This message can be particularly confusing, especially for developers working with API endpoints returning JSON data. In this post, we’ll dissect the problem and offer a clear solution.

Understanding the Error

The error occurs because the code is treating an API response, which is a JSON object, as if it were a list or array. Specifically, the response returned by the API is structured like this:

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

As you can see, it's a JSON object ({}), not an array ([]). This mismatch is what causes the error.

The Code Breakdown

In the example code provided, here’s the relevant portion that is causing the issue:

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

Issues Identified

Wrong Data Type: The response from the API is expected to be a List, but the actual response is a Map<String, dynamic>.

The Solution

To resolve the issue, you need to correctly decode the JSON object and adjust the method to handle the response accordingly. Here’s how you can fix the method:

Corrected Code

Here’s the revised getApp method:

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

Explanation of Changes:

Decode as a Map: Instead of decoding the response as a List, decode it as a Map<String, dynamic>.

Wrap in a List: Since the API only returns a single object, wrap the resulting UserModel instance in a list.

Accessing the Data

Since the response is now correctly formatted, you can access the data in your application like this:

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

This ensures that your application correctly processes the response from the API without encountering data type errors.

Conclusion

By adjusting how you handle the JSON response from your API, you can effectively resolve the '_Map<String, dynamic>' is not a subtype of type 'List<dynamic>' error in Flutter. Remember to always check the format of the data you're receiving and adjust your parsing logic accordingly.

With this guidance, you can develop your Flutter applications with greater confidence, avoiding common pitfalls related to API data handling.