Solving the Angular Material mat-chip-list Conundrum: Error Message Not Displayed When User Types Instead of Selecting from Dropdown

Are you tired of struggling with the Angular Material mat-chip-list component, only to find that error messages refuse to appear when users type in their input instead of selecting from the dropdown list? You’re not alone! In this comprehensive guide, we’ll delve into the world of Angular Material and provide a step-by-step solution to this frustrating issue.

Understanding the Problem

The Angular Material mat-chip-list component is an excellent tool for creating autocomplete functionality in your application. However, when users type in their input instead of selecting from the dropdown list, the error message often fails to display. This can lead to a poor user experience, as users may not be aware of the error and may continue to submit invalid input.

Why Does This Happen?

The reason behind this issue lies in the way the mat-chip-list component handles user input. When a user types in their input, the component doesn’t trigger the error message display. This is because the error message is tied to the selection change event, which only occurs when an item is selected from the dropdown list.

Solution Overview

To solve this issue, we’ll need to create a custom error handling mechanism that takes into account both user-typed input and selections from the dropdown list. We’ll achieve this by using a combination of Angular’s form validation and the mat-chip-list component’s built-in error handling capabilities.

Step 1: Create a Form with Mat-Chip-List Component

First, let’s create a basic form with a mat-chip-list component. We’ll use the `ReactiveFormsModule` to create a reactive form.

<form [formGroup]="myForm">
  <mat-form-field>
    <mat-chip-list #chipList formControlName="chipInput">
      <mat-chip>{{ chip }}</mat-chip>
      <input [matChipInputFor]="chipList">
    </mat-chip-list>
    <mat-error *ngIf="myForm.get('chipInput').hasError('required')>
      Please select or enter a value
    </mat-error>
  </mat-form-field>
</form>

Step 2: Add Form Validation

Next, let’s add form validation to ensure that the user either selects an item from the dropdown list or enters a valid input. We’ll use Angular’s built-in `Validators` to create a custom validator.

import { Component } from '@angular/core';
import { FormGroup, FormControl, Validators } from '@angular/forms';

@Component({
  selector: 'app-example',
  templateUrl: './example.component.html',
  styleUrls: ['./example.component.css']
})
export class ExampleComponent {
  myForm: FormGroup;

  constructor(private formBuilder: FormBuilder) { }

  ngOnInit(): void {
    this.myForm = this.formBuilder.group({
      chipInput: ['', [Validators.required, this.customValidator]]
    });
  }

  customValidator(control: FormControl): { [key: string]: boolean } | null {
    if (control.value === '') {
      return { 'required': true };
    } else {
      return null;
    }
  }
}

Step 3: Create a Custom Error Handler

Now, let’s create a custom error handler that will display the error message when the user types in their input instead of selecting from the dropdown list. We’ll use the `mat-chip-list` component’s `errorState` property to achieve this.

<form [formGroup]="myForm">
  <mat-form-field>
    <mat-chip-list #chipList formControlName="chipInput" [errorState]="getErrorState(chipList)>
      <mat-chip>{{ chip }}</mat-chip>
      <input [matChipInputFor]="chipList">
    </mat-chip-list>
    <mat-error *ngIf="myForm.get('chipInput').hasError('required')>
      Please select or enter a value
    </mat-error>
  </mat-form-field>
</form>

getErrorState(chipList): boolean {
  return this.myForm.get('chipInput').hasError('required') && chipList.inputValue !== '';
}

Step 4: Style the Error Message

Finally, let’s style the error message to ensure it’s visible and stands out to the user. We’ll add a few CSS classes to achieve this.

::ng-deep .mat-form-field {
  margin-bottom: 10px;
}

::ng-deep .mat-error {
  font-size: 12px;
  color: #f44336;
  margin-bottom: 5px;
}

Conclusion

In this article, we’ve tackled the frustrating issue of error messages not displaying when users type in their input instead of selecting from the dropdown list in Angular Material’s mat-chip-list component. By using a combination of Angular’s form validation and the mat-chip-list component’s built-in error handling capabilities, we’ve created a custom error handling mechanism that takes into account both user-typed input and selections from the dropdown list.

With these steps, you should now be able to display error messages correctly when users type in their input, providing a seamless and user-friendly experience in your application.

Troubleshooting Tips

If you’re still experiencing issues with error messages not displaying, try the following troubleshooting tips:

• Verify that you’ve correctly implemented the custom validator and error handler.
• Ensure that the `errorState` property is correctly bound to the `getErrorState` function.
• Check that the error message is correctly displayed by inspecting the HTML element.

Final Thoughts

In conclusion, Angular Material’s mat-chip-list component is a powerful tool for creating autocomplete functionality in your application. By following the steps outlined in this article, you should be able to overcome the common issue of error messages not displaying when users type in their input instead of selecting from the dropdown list.

Remember to stay calm, be patient, and don’t hesitate to reach out if you need further assistance. Happy coding!

Frequently Asked Question

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