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Learn how to resolve the `NoSuchMethodError` in Flutter while sorting JSON data, ensuring a smooth experience when handling API responses.
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This video is based on the question https://stackoverflow.com/q/62769602/ asked by the user 'Mrunal Joshi' ( https://stackoverflow.com/u/13454830/ ) and on the answer https://stackoverflow.com/a/62770783/ provided by the user 'SebastianK' ( https://stackoverflow.com/u/6769725/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Fix NoSuchMethodError When Sorting a JSON Array in Flutter

Handling JSON data can sometimes lead to errors, especially when you're sorting the contents of an array. In Flutter, encountering a NoSuchMethodError while attempting to sort a JSON array can be frustrating. In this guide, we'll explore a common scenario that leads to this error and provide a comprehensive solution. Let’s dig deeper into the problem!

The Problem: NoSuchMethodError Explained

When sorting a JSON array, you might run into an error like this:

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

This error indicates that the code is trying to access a property or method that doesn't exist on the object. Specifically, the issue occurs when you attempt to access the property value on a map (in this case, JSON objects).

A Typical Use Case

Consider that you have JSON data from an API that looks like this:

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

And you want to sort the data based on the unit_no under a specific univ_spec_sub_id. This is likely what you were attempting to achieve!

The Solution: Correcting Your Sorting Logic

Here’s how you can modify your sorting method in Flutter to avoid the error and achieve the desired sort order. Let’s break it down into understandable steps.

Step 1: Parse Your JSON Data

First, ensure that you correctly parse your JSON response:

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Step 2: Sorting Logic

You need to sort the list unitdata by two keys: univ_spec_sub_id and unit_no. Here's the correct implementation:

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

Explanation of the Sorting Logic

Compare univ_spec_sub_id: This first level of comparison ensures that all entries with the same univ_spec_sub_id are grouped together for sorting.

Compare unit_no: By converting the unit_no to an integer, we ensure a proper numerical comparison. This prevents issues where string sorting would not yield the expected order.

Step 3: Testing the Sort

To verify that your sorting implementation works correctly, you can print the sorted list or use assertions if you're developing tests:

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

Adding appropriate test cases, as shown in the original problem’s dart test, can provide confidence in the correctness of your sorting logic.

Conclusion

By following these steps and making minor adjustments to your sorting logic, you can effectively overcome the NoSuchMethodError while sorting JSON arrays in Flutter. Remember to always parse your JSON correctly and ensure that you're accessing its properties in a way that conforms to its structure.

In this guide, we covered how to sort JSON data by univ_spec_sub_id and unit_no. Now, you can confidently handle JSON responses and sort them according to your requirements. Happy coding!