AngularJS: Check if a Field Contains a MatFormFieldControl

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By squashlabs, Last Updated: December 10, 2023

AngularJS: Check if a Field Contains a MatFormFieldControl

To ensure that a mat-form-field contains a MatFormFieldControl in AngularJS, follow these steps:

Step 1: Import the necessary modules

Make sure you have imported the necessary modules in your AngularJS component. In this case, you need to import the MatInputModule module from @angular/material:

import { MatInputModule } from '@angular/material/input';

Related Article: Accessing Parent State from Child Components in Next.js

Step 2: Add the mat-form-field element

In your component’s template, add the mat-form-field element and specify the appearance attribute if needed. For example:


  <!-- Your input control goes here -->

Step 3: Add the MatFormFieldControl to your input control

Inside the mat-form-field element, add an input control and make sure it implements the MatFormFieldControl interface. This interface provides the necessary methods and properties for the mat-form-field to interact with the control. Here’s an example using the MatInput control:


  

In this example, the input control is using the MatInput directive, which already implements the MatFormFieldControl interface. You can bind your form control to the formControl property of the input control.

Step 4: Implement the MatFormFieldControl interface (if necessary)

If you are creating a custom input control and want it to work with mat-form-field, you need to implement the MatFormFieldControl interface. This involves providing implementations for the required methods and properties.

Here’s an example of a custom input control that implements the MatFormFieldControl interface:

import { Component, OnInit, OnDestroy, Optional, Self, Input } from '@angular/core';
import { ControlValueAccessor, NgControl, FormControl } from '@angular/forms';
import { MatFormFieldControl } from '@angular/material/form-field';
import { Subject } from 'rxjs';

@Component({
  selector: 'app-custom-input',
  templateUrl: './custom-input.component.html',
  styleUrls: ['./custom-input.component.css'],
  providers: [{ provide: MatFormFieldControl, useExisting: CustomInputComponent }]
})
export class CustomInputComponent implements ControlValueAccessor, MatFormFieldControl, OnInit, OnDestroy {
  // Implement the required properties and methods of the MatFormFieldControl interface
}

In this example, the CustomInputComponent class implements the MatFormFieldControl interface and is annotated with the providers array to provide itself as the implementation for MatFormFieldControl.

Related Article: How to Apply Ngstyle Conditions in Angular

Step 5: Register the custom control in the module

If you have created a custom input control and implemented the MatFormFieldControl interface, make sure to register the control in your module’s imports array. For example:

@NgModule({
  imports: [
    // ...
  ],
  declarations: [
    // ...
    CustomInputComponent
  ],
  exports: [
    // ...
    CustomInputComponent
  ]
})
export class YourModule { }

Make sure to import and declare your custom input control in your module and export it if needed.

Step 6: Validate and handle errors (if necessary)

To validate and handle errors for the mat-form-field, you can use Angular’s built-in form validation mechanisms. For example, you can use the Validators class to add validation rules to your form control. Here’s an example:

import { Validators } from '@angular/forms';

yourFormControl = new FormControl('', [Validators.required]);

In this example, the yourFormControl form control has a validation rule that requires a value to be entered.

You can also display error messages using the mat-error element inside the mat-form-field:


  
  This field is required

In this example, the mat-error element is conditionally displayed based on the required error of the yourFormControl.

Step 7: Additional considerations

– Make sure you have installed the necessary packages. You can install the required Angular Material packages by running the following command:

npm install @angular/material @angular/cdk

– It is important to follow the documentation and examples provided by the Angular Material team to ensure proper usage and compatibility.

– For more advanced scenarios and customization options, refer to the official Angular Material documentation: [Angular Material – Form Field](https://material.angular.io/components/form-field/overview)

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