Скачать или смотреть How to Filter a List of Maps and Display it in Flutter's ListView Builder

Learn how to filter a list of maps in Flutter and display the results using a ListView builder effectively. Follow our guide to enhance your Flutter application!
---
This video is based on the question https://stackoverflow.com/q/76674865/ asked by the user 'Idriss Garfa' ( https://stackoverflow.com/u/17349446/ ) and on the answer https://stackoverflow.com/a/76674921/ provided by the user 'Ildeberto Vasconcelos' ( https://stackoverflow.com/u/14158791/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to filter a list of Maps and display it inside ListView builder | Flutter | Dart

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Filtering a List of Maps in Flutter

When developing a Flutter application, managing and displaying data efficiently is crucial for a seamless user experience. One common scenario developers encounter is filtering a list of data based on specific criteria and displaying it using a ListView builder.

In this guide, we will explore how to filter a list of appointments based on the selected appointment type (Incoming/Past) and display that information in a ListView.

The Problem: Filtering Appointments

Imagine you have a list of appointments stored as maps in a static list, each containing details such as the appointment status, doctor information, and the date of the appointment. The goal is to filter this list based on whether the appointments are upcoming or past.

Here's how the appointments are structured:

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

The Challenge

While trying to filter the appointment list based on the selected status, a common error may occur. Developers might encounter a NoSuchMethodError, which indicates that a method was called on a null object. In this case, it might happen because the filtering logic is not properly implemented, leading to null values.

The Solution: Using the where Method

To effectively filter the list of appointments, it's recommended to use the where method instead of an if statement. The where method is specifically designed to filter collections based on a condition, resulting in a new iterable containing only the items that satisfy the specified condition.

Correct Approach

Here's how you can implement the filtering correctly:

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

Breaking It Down

where Method: This method is a powerful tool that allows you to filter a collection based on a function. In this case, the function checks if each appointment's status matches the _selectedAppointments variable.

Condition: The condition appointment["status"] == _selectedAppointments ensures that only appointments matching the selected status (either "Incoming" or "Past") are included in the selectedAppointmentsList.

Result Conversion: The result of the where function is then converted to a list using .toList(), which forms the new list of filtered appointments.

Displaying the Filtered Appointments

Once you have filtered the appointments correctly, you can then feed this selectedAppointmentsList into a ListView builder to display them on the screen. Here’s a simple example of how you might do that:

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

Conclusion

Filtering a list of maps in Flutter can be seamlessly achieved using the where method, which enhances code readability and avoids null errors that may occur with poorly structured filtering logic. This method not only provides a clear solution to the problem but also improves the performance and maintainability of your application code.

By following these steps, you can ensure that your Flutter app efficiently manages and displays data to users, leading to a better overall experience.

Now that you have the know-how, go ahead and integrate filtering into your Flutter app!