Custom Component in Angular with ngModel and multiple fields

Question

So lets say I want a create a custom component in Angular 2+ for the following class

public class user {
    name: string;
    id: number;
    address: string;
}

I've created a custom component

<input [(ngModel)]="name" />
<input [(ngModel)]="id" />
<input [(ngModel)]="address" />

I've added this custom component into my main page

<user-component></user-component>

What I want to do now is pass the User class as ngModel inside my custom component and bind it with public user:User variable in my main page class. Something like this

<user-component [(ngModel)]="user"></user-component>

I've found few examples of using ControlValueAccessor, NG_VALUE_ACCESSOR but all these examples work with single component like one text input. Is there a way to make it work for multiple inputs inside the custom component as well?

you should use reactive forms

Patricio Vargas
– Patricio Vargas

2019-09-11 07:03:25 +00:00
Commented Sep 11, 2019 at 7:03 — Patricio Vargas
– Patricio Vargas, Commented Sep 11, 2019 at 7:03

Simplicity's_Strength · Accepted Answer · 2019-09-11 07:34:18Z

7

The way to achieve this is to use @Input on the UserComponent

export class UserComponent {
  @Input() user: User;
}

Then binding to the input you declared in your parent template

<user-component [user]="user"></user-component>

Now this is only one way, input to the UserComponent,

To make it two ways like ngModel works you would need to add the output EventEmiter As follows

export class UserComponent {
  @Input() user: User;
  @Output('userChange') emitter: EventEmitter<User> = new EventEmitter<User>();
}

Note that the userChange keyword is important here to make it work.

Only then you would be able to write the two way binding

<user-component [(user)]="user"></user-component>

Adding a bit of reading docs here angular.io/guide/template-syntax#property-binding-property

Also with just a google search away, i was able to find this also good SO answer on the same topic custom-input-and-output-on-same-name-in-angular2-2-way-binding

answered Sep 11, 2019 at 7:34

Simplicity's_Strength

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5 Comments

Simplicity's_Strength Over a year ago

As everyone is pointing out, a nice life saver would be to use angular.io/guide/reactive-forms#grouping-form-controls a FormGroup with FormControls inside

casper123 Over a year ago

If I use reactive forms, will I get two way data binding ?

Simplicity's_Strength Over a year ago

Reactive forms help to manage values and validity of the inputs. For example you can subscribe to a FormControls change events. You still need the input outputs on the component to notify the parent component.

Eliseo Over a year ago

@Simplicity's_Strength, is an object, it's NOT necesary @Output, see e.g. stackblitz.com/edit/…

Simplicity's_Strength Over a year ago

@Eliseo good point, this two way binding example is not needed in case you can bind to the Object directy. Your answer and stackblitz are valids for OPs initial need.

Eliseo · Accepted Answer · 2019-09-11 07:28:43Z

1

as you has an object you can simple pass the object as @Input and

<user-component [user]="user"></user-component>

And your child

@Input() user:any

<input [(ngModel)]="user.name" />
<input [(ngModel)]="user.id" />
<input [(ngModel)]="user.address" />

NOTE: Really I love ReactiveForms, cheer up to use these

answered Sep 11, 2019 at 7:28

Eliseo

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1 Comment

casper123 Over a year ago

Yes I can pass the object, but once user updates the input fields inside custom component, will I get updated filed values in main component ?

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