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Discover how to effectively manage asynchronous validation in Angular with TypeScript using promises, ensuring seamless execution of your plan without exceptions.
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Handling Asynchronous Validation in Angular with TypeScript

In modern web development, especially when working with frameworks like Angular, handling asynchronous operations can be quite challenging. One common scenario developers encounter is performing validations that may throw exceptions, where you need to manage these exceptions gracefully during asynchronous operations.

Let’s break down a specific problem related to asynchronous validation and explore how to solve it effectively.

The Problem: Skipped Actions on Exception

Consider the following situation: you are trying to validate a plan by performing two checks asynchronously. If either of the checks fails, you want to skip subsequent actions. However, due to the asynchronous nature of the checks, your code proceeds to the next action regardless of whether an exception is thrown or not.

Here’s the initial code snippet that demonstrates this issue:

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Key Issue

The problem here is that since the checks are happening asynchronously using subscriptions, the try/catch block does not catch the exceptions thrown inside the subscription. Consequently, the completePlanConfirm() method eventually gets executed, even when an error occurs in validation.

The Solution: Using Promises with Async and Await

To handle this situation effectively, we can utilize async and await alongside promises. By converting your observables to return promises, you can streamline the code and improve error handling for the validations. This allows you to wait for each validation check to complete before moving on to the next step.

Step-by-Step Implementation

Convert Validation Checks to Promises
Create functions that perform checks and return promises.

Update the Complete Function
Use async and await to wait for the checks to finish before executing the confirmation method.

Here’s how the improved code would look:

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Explanation of the Improved Code

Async/Await: The completePlan function is declared as async, allowing the use of await for asynchronous operations.

Promise Handling: The checkFirstPlan and checkSecondPlan methods are modified to return Promise. If the checks fail, we call reject with an error, which gets caught in the completePlan function.

Error Management: By using a combined approach of async/await and promises, we can handle errors in a straightforward manner without complicating our flow with multiple subscriptions.

Conclusion

By mastering the use of async and await along with promises, you can efficiently handle asynchronous validation in Angular applications. This leads not only to simpler code but also to improved error handling and user experience. Implementing these changes will ensure that your application logic flows as intended, bypassing subsequent actions when necessary. Consider this approach next time you face validations in an async environment!