Extending Angular 2 ngModel directive to use observables

Do you really want to create an observable for each input field in your form? The pattern I use is to have one observable for the model of the whole form, clone it for a view variable that you can then bind to and then have the submit handler of the form push the new model back to the service.

user$ = this.userService.user$;

save(user: User) {
  this.userService.save(user);
}

and in the view

<form *ngIf="user$ | async | clone as user" #userForm="ngForm" (submit)="userForm.form.valid && save(user)">
  <label>
    Firstname
    <input name="firstname" [(ngModel)]="user.firstname" required>
  </label>
  <label>
    Lastname
    <input name="lastname" [(ngModel)]="user.lastname" required>
  </label>
  <button>Save</button>
</form>

The clone pipe looks like this

export const clone = (obj: any) =>
  Array.isArray(obj)
    ? obj.map(item => clone(item))
    : obj instanceof Date
    ? new Date(obj.getTime())
    : obj && typeof obj === 'object'
    ? Object.getOwnPropertyNames(obj).reduce((o, prop) => {
        o[prop] = clone(obj[prop]);
        return o;
      }, {})
    : obj;

import { Pipe, PipeTransform } from '@angular/core';

import { clone } from './clone';

@Pipe({
  name: 'clone'
})
export class ClonePipe implements PipeTransform {

  transform(value: any): any {
    return clone(value);
  }
}

I have done a write up on this pattern with my state management library here. https://medium.com/@adrianbrand/angular-state-management-with-rxcache-468a865fc3fb

I came up with a similar approached to @Adbel. Not sure about the inner implications of this, but it will be awesome to have some feedback. Stackbliz code

Your.component.ts

export class AppComponent  {
  email = new BehaviorSubject("UnwrappedMe 😱");

  emailHandler(input) {
    this.email.next(input);
  }
}

Your.component.html

 <form class="mx-3">
     <input [ngModel]="email | async" 
            (ngModelChange)="emailHandler($event)" 
            name="email" type="email" 
            id="email" placeholder="Enter email">
 </form>

 <p class="mx-3"> {{ email | async }} </p>

A little variation in case you need to get a ref to your input value and you do not want to make a second subscription (use template vars).

Your.component.html

 <form class="mx-3">
     <input [ngModel]="email | async" #emailref
            (ngModelChange)="emailHandler($event)" 
            name="email" type="email" 
            id="email" placeholder="Enter email">
 </form>

 <p class="mx-3"> {{ emailref.value }} </p>

I don't know why you wouldn't just use reactive forms, but this was a fun puzzle. I created a directive that will alter the model value to the BehaviorSubject's value. And any changes will call .next on the BehaviorSubject for you.

Usage will look like this

<input type="text" [ngModel]="ngModelValue" appRxModel> 

Here is the stackblitz, enjoy