Resolving a Mandatory Unavoidable Circular Dependency in Angular 9

Learn how to effectively manage session timeouts and eliminate circular dependencies in Angular 9 applications.
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This video is based on the question https://stackoverflow.com/q/65833106/ asked by the user 'niraja k' ( https://stackoverflow.com/u/9107787/ ) and on the answer https://stackoverflow.com/a/65840451/ provided by the user 'Ashot Aleqsanyan' ( https://stackoverflow.com/u/11769164/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Addressing a Mandatory Unavoidable Circular Dependency in Angular 9

In modern web applications, managing user sessions is critical for maintaining security and usability. Angular 9 provides robust tools for handling sessions, but developers may encounter challenges like circular dependencies when implementing features such as session timeouts. In this post, we’ll explore a common issue that arises when trying to manage session timeouts and present a clear solution to handle it effectively.

The Problem: Circular Dependency in Session Timeout Logic

Imagine you have a session timeout feature where:

After a successful login, a timeout initiates a prompt to the user after a set duration (e.g., 1 hour).

If the user is inactive, a dialog appears asking whether they want to stay connected or be logged out. If they choose to stay connected, the dialog calls the timeout function again. Here lies the problem: this creates a circular dependency where the dialog keeps calling itself indefinitely.

Let’s break down the provided code and understand where this circularity might occur:

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

In this code, when the user clicks “stay connected,” it re-triggers setSessionTimer, which ultimately leads to openTimeOutDialog being called again, resulting in a loop. To resolve this, we need a different approach.

The Solution: Using Dialog Close Listener

One effective way to avoid this circular dependency is by listening for the dialog’s close event and handling it accordingly. Here’s how you can implement this solution step-by-step.

Step 1: Modify the openTimeOutDialog Method

First, let’s change the way the dialog is handled in the openTimeOutDialog method:

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

Explanation:

afterClosed(): This method returns an observable that you can subscribe to. It emits a value when the dialog is closed.

response.startSession: You can send back a value from the dialog’s component indicating whether the user chose to stay connected. Depending on that response, you can restart the session timer.

Step 2: Implementing the Dialog Component

Next, ensure the modal component closes correctly and sends back the necessary signal. Here’s an example of what the dialog component might look like:

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

Explanation:

Within the dialog component, the onContinue method closes the dialog and sends back an object indicating that the session should be restarted.

Conclusion

By making these adjustments, you not only prevent circular dependencies but also create a responsive user experience by managing session timeouts effectively in Angular 9. Remember, listening to events such as dialog closures can provide improved control over application flow and resource management.

Implementing the above steps will enhance your Angular application's session management capabilities while maintaining clarity and efficiency in your code structure. Happy coding!