Скачать или смотреть Resolving the List dynamic is not subtype of type Map String, dynamic Error in Flutter

Learn how to fix the `List dynamic is not subtype of type Map String, dynamic ` error in Flutter when working with API data. Follow our detailed guide for seamless integration.
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This video is based on the question https://stackoverflow.com/q/65811498/ asked by the user 'Billy Noyes' ( https://stackoverflow.com/u/7791406/ ) and on the answer https://stackoverflow.com/a/65811903/ provided by the user 'Shubham Narkhede' ( https://stackoverflow.com/u/12096653/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting Flutter: The List<dynamic> is not subtype of type Map<String, dynamic> Error

When developing applications using Flutter, encountering errors while working with APIs is a common hurdle. One such error that may come up is the infamous List<dynamic> is not subtype of type Map<String, dynamic>. This typically occurs when you are trying to decode JSON data from an API but the structure of your data doesn’t align with what your code expects. In this guide, we will delve into the details of this error and provide you with a structured solution to fix it effectively.

Understanding the Problem

In your scenario, you are accessing an API to retrieve sale information that includes a website, sale title, and sale code. You encounter the error when trying to convert the JSON response into a model that Flutter can work with.

Common Cause

The error indicates that while your code is trying to interpret the API response as a single Map, the actual response is a List of Maps. This mismatch leads to the error. It’s essential to understand the structure of the JSON data you are working with to address this issue gracefully.

Step-by-Step Solution

To resolve this error, you’ll need to adjust your code to handle the response correctly as a List of SaleAlert objects rather than a single SaleAlert object. Let’s break down this solution into manageable steps.

1. Modify the API Call Method

You need to revise your API fetch method to accommodate the List response. Here’s how:

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

2. Update Your FutureBuilder

Ensure that your FutureBuilder is now set to handle a List of SaleAlert objects:

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

3. Clean Up initState

Since you are now fetching the alert directly in the FutureBuilder, you can remove the API call from the initState method to prevent redundancy:

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

Conclusion

By adjusting the method in which you handle the API response, you can effectively fix the List<dynamic> is not subtype of type Map<String, dynamic> error in Flutter. This ensures that the data types are aligned with the expected structures, allowing your application to run smoothly.

If you find yourself facing this issue or similar ones, remember the key takeaway: always ensure that your data parsing aligns with the structure of the JSON you receive.

We hope this guide has helped you troubleshoot the problem and provided you with a clearer understanding of working with JSON in Flutter. Happy coding!