Скачать или смотреть Resolving the No Such Method Error: The Getter Data was Called in Null Response in Flutter and Dart

Learn how to troubleshoot and resolve the `No Such Method Error` in Flutter by implementing a robust JSON response model using the `freezed` and `json_serializable` packages, ensuring smooth integration of API data.
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This video is based on the question https://stackoverflow.com/q/76312974/ asked by the user 'AzeTech' ( https://stackoverflow.com/u/9805273/ ) and on the answer https://stackoverflow.com/a/76313263/ provided by the user 'Luca Iaconelli' ( https://stackoverflow.com/u/3359931/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving the No Such Method Error: The Getter Data was Called in Null Response in Flutter and Dart

When building mobile applications with Flutter, developers often encounter issues related to handling asynchronous data, especially when fetching and parsing data from APIs. One common obstacle is the No Such Method Error, which occurs when attempting to access a property of a non-existent object or a null response. In this guide, we’ll explore a specific case involving a JSON response model, aimed at addressing this issue effectively.

The Problem Explained

Imagine you have an API that returns a JSON object with success and data fields. You are trying to access specific properties within that data, but you receive a No Such Method Error, indicating that the property you are trying to access is being called on a null object. This issue often arises from incorrectly set up models, improper API request handling, or misunderstanding how to access nested data structures.

Consider the JSON response below, which should ideally contain a list of news articles:

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In the example where the error occurs, you may attempt to access the news list from the JSON response without ensuring that the response is properly mapped to the corresponding Dart model.

Solution Breakdown: Using Freezed and Json Annotation

To resolve this error, we can leverage the power of Dart packages like freezed and json_annotation to create a robust model for our JSON response. This will help to ensure we can easily parse the data without encountering null-related issues.

Step 1: Define the Data Model

First, create a model to represent the JSON response using the freezed and json_annotation packages. Here’s how you can set it up:

Add dependencies to your pubspec.yaml:

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Create your model classes:

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Step 2: Fetch Data Correctly

Next, modify your method to fetch news using the newly created data model:

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Step 3: Accessing Data in FutureBuilder

Now, update your FutureBuilder to access the newly structured data without running into null issues:

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Conclusion

By defining a clear and structured data model using freezed and json_annotation, and correctly handling the fetching of your API data, you can prevent errors such as the No Such Method Error. This not only enhances code reliability but also improves the overall quality of your Flutter application.

If you have faced similar issues or have additional tips, feel free to share them in the comments! Happy coding!