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Learn how to handle null values in data models effectively by updating them with appropriate value types in Flutter and Dart.
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This video is based on the question https://stackoverflow.com/q/70335684/ asked by the user 'Filipe Gonçalves Ribeiro Costa' ( https://stackoverflow.com/u/17398659/ ) and on the answer https://stackoverflow.com/a/70335762/ provided by the user 'ahmetakil' ( https://stackoverflow.com/u/7441113/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Update Your Model with the Correct Value Type in Flutter/Dart

When working with Flutter and Dart, especially when dealing with data fetched from the internet, you may encounter situations where your model might receive null values for fields that ideally require specific default values. This can cause your application to throw errors or break while trying to use those null values. In this guide, we will explore how to effectively handle such scenarios in your models and update them with the corresponding correct value types.

The Problem

In the provided code, we fetch data from an API using an HTTP GET request. The obtained response can contain null values for certain keys in the JSON, which do not align with the expected data types of the model fields. For instance:

An integer field receiving null should be set to 0.

A boolean field returning null should be set to false.

A string field returning null should default to an empty string "".

A list field returning null should default to an empty list [].

The original code replaces only string values with empty strings but results in a crash when encountering null values in other types, like integers.

Example Response:

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

Desired Response:

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

The Solution: Using the fromJson Function

Instead of updating the response body directly, we can use the fromJson function in our model class to supply default values. This method allows us to specify what value should be assigned in case the value fetched is null.

Implementation Steps:

Update the CfoModel Class:
Ensure your CfoModel class defines a fromJson constructor, where you can handle the null checks effectively.

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

Benefits of this Approach:

Clarity: The values are set according to their expected types within a single place (the constructor), making your code more readable and maintainable.

Error Handling: This method inherently guards against nulls without explicitly modifying your data before creating a model instance.

Customizability: If your default values ever need to change, you only have to update them in the fromJson method.

Conclusion

Handling null values, especially in dynamic data fetched from APIs, is crucial for ensuring robust applications. By leveraging the fromJson constructor in your Flutter/Dart model classes, you can effectively replace null values with appropriate types, preventing runtime errors and creating a smoother user experience.

By applying these practices, you can make sure that your data models are resilient and your application performs reliably, no matter what data comes through.

Feel free to share your thoughts or any additional tips you might have for managing model values in Dart and Flutter below!