Handling multiple asynchronous operations in Dart: A comprehensive guide

In modern app development, handling multiple asynchronous tasks is a common requirement. Whether you are fetching data from multiple APIs, performing background jobs, or managing multiple animations, asynchronous programming in Dart allows you to handle these tasks efficiently.

In this blog, we'll explore different use cases where you need to make multiple asynchronous calls and provide detailed solutions using Dart. We'll go through various examples to show how Dart's Future, await, and Future.wait can be used to handle multiple asynchronous operations effectively.

What is Asynchronous Programming in Dart?

Asynchronous programming in Dart enables non-blocking operations, such as making network requests, reading/writing files, or performing animations. This prevents the app from freezing or becoming unresponsive during these tasks.

Key concepts:

• Future: A Future represents a value that will be available in the future after some asynchronous operation is completed.

• await: Pauses the execution until the Future is resolved.

• Future.wait: Waits for multiple Future operations to complete before proceeding.

Use Case 1: Fetching Data from Multiple APIs and Aggregating Results

Scenario:

You need to fetch data from multiple APIs and display the results only after receiving data from all of them. This is a common case in data aggregation, where you want to show results only after gathering data from all sources.

Solution:

Use Future.wait to perform multiple API calls simultaneously and wait until all are completed.

Explanation:

• Future.wait([...]): Initiates both API calls and waits for all of them to complete.

• The results are processed only after all the calls return successfully.

• If any API call fails, an error is handled and printed accordingly.

Use Case 2: Uploading Multiple Files Sequentially

Scenario:

You have multiple files to upload, but you want to upload them one by one, ensuring that each upload completes before the next one starts.

Solution:

Use await inside a for loop to upload files sequentially.

Explanation:

• for loop: Ensures that each file upload is awaited before the next one begins.

• Sequential file uploads are useful when there’s a dependency on each upload completion, or when server constraints require limiting concurrent uploads.

Use Case 3: Simultaneous Database Queries

Scenario:

You need to perform multiple queries on a database, such as fetching user details and their associated orders. All queries should be executed simultaneously, and the results should be processed together.

Solution:

Use Future.wait to perform multiple database queries in parallel.

Explanation:

• Future.wait([...]): Executes both database queries in parallel and waits for all results before processing them.

• This method saves time compared to running the queries sequentially.

Use Case 4: Chaining Multiple API Calls (Dependent Calls)

Scenario:

You need to fetch an authentication token from one API and use that token to fetch data from another API. In this case, the second API call depends on the success of the first.

Solution:

Chain the API calls using await.

Explanation:

• The second API call depends on the token from the first API. The await keyword ensures the second call only happens after receiving the token.

• This is useful in situations where the first API call is required for authentication or session management.

Use Case 5: Running Multiple Background Jobs Simultaneously

Scenario:

You want to run several independent background jobs and execute further code after all jobs are finished.

Solution:

Use Future.wait to run all background tasks and wait for completion.

Explanation:

• Multiple background tasks are initiated simultaneously using Future.wait.

• This is useful when you have several independent tasks that can run in parallel, like data processing, file generation, etc.

Use Case 6: Waiting for Multiple Animations to Complete

Scenario:

You want to perform an action after two animations complete, such as transitioning between screens or revealing multiple UI elements.

Solution:

Use Future.wait to handle multiple animation controllers.

Explanation:

• Both animations are started simultaneously and Future.wait ensures the code waits until both complete.

• This is helpful when synchronizing multiple visual elements in a UI.

Use Case 7: Performing Multiple File Reads Simultaneously

Scenario:

You need to read multiple files from the file system simultaneously and process the content once all files are read.

Solution:

Use Future.wait to read files in parallel.

Explanation:

• Both file read operations are initiated simultaneously, which speeds up I/O-bound tasks.

• This is useful for processing large files or configurations at startup.

Use Case 8: Polling Multiple Services

Scenario:

You need to monitor the status of multiple services by polling their status APIs at regular intervals.

Solution:

Use Future.wait in combination with a loop or timer to poll services simultaneously.

Explanation:

• Both service status requests are performed in parallel, ensuring fast response times.

• Polling is often required to check the health or status of external systems in real-time applications.

Conclusion

Asynchronous programming in Dart provides powerful mechanisms to manage multiple tasks efficiently. Whether you're dealing with API calls, file I/O, animations, or background jobs, using Future, await, and Future.wait allows you to handle multiple tasks simultaneously and ensure smooth performance.

By understanding these patterns, you can ensure that your applications remain responsive, efficient, and capable of managing multiple operations concurrently.