formGroup expects a FormGroup instance

Question

I have an Angular 2 RC4 basic form example on Plunkr that appears to throw the following error (In Chrome DEV console)

Here's the plunkr

https://plnkr.co/edit/GtPDxw?p=preview

Error:

browser_adapter.ts:82 EXCEPTION: Error: Uncaught (in promise): EXCEPTION: Error in ./App class App - inline template:1:7
ORIGINAL EXCEPTION: formGroup expects a FormGroup instance. Please pass one in.
           Example: <form [formGroup]="myFormGroup">

ORIGINAL STACKTRACE:
Error: formGroup expects a FormGroup instance. Please pass one in.
           Example: <form [formGroup]="myFormGroup">

    at new BaseException (https://npmcdn.com/@angular/forms@0.2.0/src/facade/exceptions.js:27:23)
    at FormGroupDirective._checkFormPresent (https://npmcdn.com/@angular/forms@0.2.0/src/directives/reactive_directives/form_group_directive.js:110:19)
    at FormGroupDirective.ngOnChanges (https://npmcdn.com/@angular/forms@0.2.0/src/directives/reactive_directives/form_group_directive.js:39:14)
    at DebugAppView._View_App0.detectChangesInter

Answer 1

There are a few issues in your code

• <div [formGroup]="form"> outside of a <form> tag
• <form [formGroup]="form"> but the name of the property containing the FormGroup is loginForm therefore it should be <form [formGroup]="loginForm">
• [formControlName]="dob" which passes the value of the property dob which doesn't exist. What you need is to pass the string dob like [formControlName]="'dob'" or simpler formControlName="dob"

Plunker example

Answer 2

I was using reactive forms and ran into similar problems. What helped me was to make sure that I set up a corresponding FormGroup in the class. Something like this:

myFormGroup: FormGroup = this.builder.group({
    dob: ['', Validators.required]
});

Answer 3

I had this error when I had specified fromGroupName instead of formArrayName.

Make sure you correctly specify if it is a form array or form group.

<div formGroupName="formInfo"/>

<div formArrayName="formInfo"/>