Скачать или смотреть Understanding Why pushNewScope and popScope Don't Work as Expected in GetIt

Discover the common pitfalls of using `pushNewScope` and `popScope` in GetIt and learn the correct approach to manage instances effectively in your Flutter or Dart applications.
---
This video is based on the question https://stackoverflow.com/q/71855613/ asked by the user 'happyhappy' ( https://stackoverflow.com/u/16765312/ ) and on the answer https://stackoverflow.com/a/71856170/ provided by the user 'happyhappy' ( https://stackoverflow.com/u/16765312/ ) 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: Why does pushNewScope/popScope not work for Getit?

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.
---
Understanding pushNewScope and popScope in GetIt: A Guide to Proper Usage

When working with the GetIt dependency injection library in Flutter or Dart, the functionality for managing scopes is often misunderstood. Developers frequently encounter issues like the one described in the question: “Why does pushNewScope/popScope not work for GetIt?” Understanding the correct usage of these methods is crucial for effective dependency management in your applications. Let’s delve into this problem and its solution in detail.

The Problem: Instance Registration Conflicts

In the provided code snippet, the developer attempts to create a new instance of ProductDatabase after pushing a new scope using the pushNewScope() method. However, they encounter an error stating that the instance is already registered. This confusion usually arises due to improper handling of asynchronous operations and the lifecycle of scopes with GetIt.

Code Explanation

Here’s the code we’re working with:

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

db1 retrieves an instance of ProductDatabase from the default scope.

pushNewScope() creates a new scope for the registration of instances.

registerSingleton(ProductDatabase()) registers a new instance of ProductDatabase in the new scope.

db2 attempts to retrieve the new instance, but it results in an error because it conflicts with the existing registration of the ProductDatabase from the default scope.

popScope() is supposed to return to the previous scope, but it won’t resolve the issue unless handled properly.

The Solution: Await the popScope() Call

The key to resolving the issue lies in understanding the asynchronous nature of scope management in GetIt. The solution is straightforward but crucial for effective dependency management. Here’s how to implement it correctly:

Steps to Use pushNewScope and popScope Effectively

Push a New Scope: Start by preparing to create a new environment for instance registration.

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

Register Your Instance: Register a new instance of the ProductDatabase within the new scope.

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

Retrieve the Instance: Now, retrieve the newly registered instance.

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

Pop the Scope Asynchronously: The most critical step is ensuring you await the popScope() call, which reverts to the previous scope. You should do this one line at a time, including it as part of an asynchronous function.

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

Retrieve the Previous Instance: After popping the scope, you can access the original instance of ProductDatabase seamlessly without any conflicts.

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

Example: Complete Correct Implementation

Here’s a complete and correct example of how to implement the above steps in a function.

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

Conclusion

Understanding how to use pushNewScope and popScope in GetIt can greatly enhance your dependency management skills in Flutter or Dart applications. Always remember to await the popScope() method to ensure that your scope transitions operate smoothly. With the steps outlined above, you should now be equipped to handle multiple instances of the same object seamlessly, avoiding conflicts and boosting the modularity of your application.

Implement these practices in your next project to see the difference it can make in your dependency injection strategy!