使用ngModel指令和value属性更新表单

Question

I am trying to edit some data in my MEAN stack app and I am using Reactive Form . I am using ngModel two way data binding and HTML input's value attribute. As I am populating my form using value attribute I successfully get the required data from my API into the Input fields but when I click on the Submit Button . Form returns null back and all the fields in my MongoDB gives me null back.This is the method i'm running on submit.

 editPatient() {
 const patient = {
  first_name: this.first_name,
  last_name: this.last_name,
  DOB: this.DOB,
  email: this.email,
  address: this.address,
  city: this.city,
  province: this.province,
  postal_code: this.postal_code,
  phone: this.phone,
  department: this.department,
  doctor: this.doctor
}
this.patientService.updatePatient(this.ID, patient).subscribe((patient: any) => {
  console.log(patient);
})}

This is my HTML's single div. I have couple more but logic is same in those as well

<div class="form-group" [ngClass]="{'is-invalid':formErrors.first_name}">
  <label>First Name</label>
  <input type="text" placeholder="First Name" [(ngModel)]="first_name" formControlName="first_name" class="form-control"
    (blur)="logValidationErrors()" value={{patient.first_name}} required>
  <span class="help-block" *ngIf="formErrors.first_name">
    {{formErrors.first_name}}
  </span>
</div>

As of now what I think my problem is when i use two way binding it expects value user enters in the input field but it doesn't read/consider what it gets from value attribute as a user input data and returns empties back. This is my deduction if it's true I have no idea how I can bind value attribute to ngModel . Is there any other work around possible to achieve this?

Answer 1

Since you're using the Reactive Forms approach, you should be using just the [formGroup] , and formControlName directives on the Template instead of using [(ngModel)] .

You can then get the value of your form using this.yourFormName.value

In your Component Class:

...

constructor(
  private fb: FormBuilder,
  private patientService: PatientService
) {}

ngOnInit() {
  ...
  this.patientEditForm = this.fb.group({
    first_name: [],
    last_name: [],
    DOB: [],
    email: [],
    address: [],
    city: [],
    province: [],
    postal_code: [],
    phone: [],
    department: [],
    doctor: []
  });
  ...
}

...

editPatient() {
  this.patientService.updatePatient(this.ID, this.patientEditForm.value)
    .subscribe((patient: any) => {
      console.log(patient);
    })
}

...

In your Template:

<form [formGroup]="patientEditForm" ...>
  ...
    <div class="form-group" [ngClass]="{'is-invalid':formErrors.first_name}">
        <label>First Name</label>
    <input type="text" placeholder="First Name" formControlName="first_name" class="form-control"
      (blur)="logValidationErrors()" value={{patient.first_name}} required>
    <span class="help-block" *ngIf="formErrors.first_name">
      {{formErrors.first_name}}
    </span>
  </div>
  ...
</form>