How to Show an Error Message After Exceeding maxLength in Angular Dynamic FormArray

This guide explains how to effectively display error messages for `maxLength` validation in an Angular Dynamic FormArray. Step-by-step guidance included!
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How to Show an Error Message After Exceeding maxLength in Angular Dynamic FormArray

When building forms in Angular, especially dynamic forms, validation plays a crucial role in ensuring that the data entered is accurate and conforms to expected formats. One common validation scenario is enforcing a maximum length for input fields. If you’re working with a dynamic FormArray, you may encounter challenges displaying error messages upon exceeding the maxLength limit. In this post, we’ll guide you through resolving this issue in an Angular application.

Problem Overview

In dynamic forms created using Angular's reactive forms, developers sometimes need to implement validations like maxLength on fields. However, after setting up the form and applying these validations, you might find that error messages are not displaying as intended when the input exceeds the maximum length.

For instance, suppose you want to validate input for a field and show an error message like "Max 7 characters" if the user exceeds 7 characters. You may try various conditions but end up with errors such as "hasError is not a function" or "Parser Error."

Understanding the Solution

The good news is that the solution is straightforward once you leverage the existing references correctly. Here’s how to go about it:

Step 1: Adjust the Template

When using an *ngFor loop to display controls in your FormArray, you already have access to the individual FormGroup. You do not need to access the control at the top level of the form using complex chaining. Instead, you should directly reference the control in each iteration.

Here’s a refined way to check for errors:

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

Step 2: Ensure Error Key is Proper

In your code, ensure that the error key for max length is correctly referenced. Angular's validation keys are case-sensitive, so make sure to use maxlength in all lowercase:

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

Key Implementation Points

Use get() Method: Retrieve controls using the get() method directly on the node variable inside your loop. This bypasses the need for unnecessary complex references.

Correct Error Key: Always use lowercase for validation keys (maxlength).

Reusable Code: Make modifications in reusable components or services for maintainability.

Conclusion

By following these steps, you can effectively show an error message when the input for your dynamic form exceeds the specified maxLength. Properly using the get() method in combination with accurately checking error keys will keep your validation logic straightforward and intuitive.

If you have any more questions or need further assistance with Angular forms, feel free to ask in the comments below!