Angular Component variables returning undefined

Question

I'm using Angular 10, and i'm havin issues to create a Input Component with ControlValueAccessor.

I'm creating public vars and public arrow functions, and when I call the arrow function is returning undefined.

Here is my .ts code:

import { Component, forwardRef, Input } from '@angular/core';
import { ControlValueAccessor, FormControl, FormGroup, NG_VALUE_ACCESSOR } from '@angular/forms';


@Component({
    selector: 'app-input',
    templateUrl: './input.component.html',
    styleUrls: ['./input.component.scss'],
    providers: [
        {
            provide: NG_VALUE_ACCESSOR,
            useExisting: forwardRef(
                () => InputComponent
            ),
            multi: true
        }
    ]
})
export class InputComponent implements ControlValueAccessor {
    @Input() public parentForm: FormGroup;
    @Input() public fieldName: string;
    @Input() public label: string;

    public value: string;
    public changed: ( value: string ) => void;
    public touched: () => void;
    public isDisabled: boolean;

    get formField (): FormControl {
        return this.parentForm?.get( this.fieldName ) as FormControl;
    }

    constructor () { }

    public writeValue ( value: string ): void {
        this.value = value;
    }

    public onChange ( event: Event ): void {
        const value: string = (<HTMLInputElement>event.target).value;
        this.changed( value );
    }

    public registerOnChange ( fn: any ): void {
        this.changed = fn;
    }

    public registerOnTouched ( fn: any ): void {
        this.touched = fn;
    }

    public setDisabledState ( isDisabled: boolean ): void {
        this.isDisabled = isDisabled;
    }
}

And my .html file:

<div class="form-group">
  <label class="form-label" [for]="fieldName">
    {{ label }}
  </label>

  <input
    type="text"
    class="form-control"
    [ngClass]="{ 'has-error': formField?.invalid && formField?.dirty }"
    [id]="fieldName"
    [name]="fieldName"
    [value]="value"
    [disabled]="isDisabled"
    (input)="onChange( $event )"
    (blur)="touched()"
  />

  <app-field-errors [formField]="formField">
  </app-field-errors>
</div>

When I interact with the Input (change/input or blur) I get this errors:

ERROR TypeError: this.changed is not a function

ERROR TypeError: ctx.touched is not a function

I believe the this.changed error is because I'm calling on onChange function, and ctx.touched is because i'm calling on HTML file.

I can access normally the Input() vars, like parentForm, fieldName and label.

Thanks for you help.

Andrew Allen · Accepted Answer · 2021-05-12 00:52:22Z

1

Change these lines

    public changed: ( value: string ) => void;
    public touched: () => void;

to

    public changed: any = ( value: string ) => void; // personally I prefer {} rather than void
    public touched: any = () => void;

answered May 12, 2021 at 0:52

Andrew Allen

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3 Comments

Rodrigo Roberto de Almeida Over a year ago

I'm changed and i'm getting no errors, but my values is not changing, still null on FormGroup. You can help me with this too?

Andrew Allen Over a year ago

I'm afraid I have to go but I have working stackblitz on one of my old answers. Binding via [formControl]="myControlName" will call the register functions interally and onChanged will update the parent form value. If you update the question someone may be able to help, I may return to this at some point

Rodrigo Roberto de Almeida Over a year ago

Using formControl ist working now, thanks alot!

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