Скачать или смотреть How to Properly Wait for a Loop to Complete in Dart/Flutter with Async/Await

Discover how to use `async/await` in Dart/Flutter to ensure your loops complete before proceeding. This guide breaks down creating a future function for smooth, asynchronous execution.
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This video is based on the question https://stackoverflow.com/q/66981864/ asked by the user 'SylvainJack' ( https://stackoverflow.com/u/15349168/ ) and on the answer https://stackoverflow.com/a/66984832/ provided by the user 'Mohamed Nagdy' ( https://stackoverflow.com/u/12131813/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Mastering Asynchronous Programming in Dart/Flutter

In the world of Dart and Flutter, handling asynchronous operations can sometimes lead to confusion—especially when it comes to loops that are expected to complete before subsequent operations can begin. If you've faced the frustrating issue of encountering a "Getter length called on null" error in your projects, this post is for you.

The Problem: Incomplete Processing of Data

Suppose you have a function that processes a large list. Within this function, you attempt to create a sublist, and then immediately perform further operations like deleting duplicates and sorting. If the initial list is substantial, you may run into a problem where these subsequent operations start before the loop has finished—resulting in errors due to incomplete data.

Example Scenario

Consider the following snippet of code that attempts to create a sublist from a large list called wordBank:

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The above code works fine for smaller lists but can throw an error when dealing with large data sets.

The Solution: Using Async/Await

To ensure that your loop completes its work before moving on to subsequent operations, you can leverage async/await by transforming your looping logic into a function that returns a Future. Below, I’ll take you through the steps required to implement this solution effectively:

Step 1: Create a Future Function

You’ll want to encapsulate the looping logic in a separate function that returns a Future. This allows you to use await when calling this function in your main execution flow:

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Step 2: Use the Future Function with Async/Await

With your function now established to return a Future, you can call it inside your original asynchronous method using the await keyword. As a result, the rest of the operations will only commence after the list is fully populated:

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Conclusion

By utilizing async/await, you can effectively manage data processing in Dart and Flutter with large data sets. This method ensures that all subsequent operations wait for the completion of your loops—leading to fewer errors and smoother performance.

Now you can confidently tackle data processing tasks, knowing that your operations are performed in a synchronous manner, even when loops are involved. Happy coding!