ChatGPT解决这个技术问题 Extra ChatGPT

Can't bind to 'formGroup' since it isn't a known property of 'form'

The situation

I am trying to make what should be a very simple form in my Angular application, but no matter what, it never works.

The Angular version

Angular 2.0.0 RC5

The error

Can't bind to 'formGroup' since it isn't a known property of 'form'

https://i.stack.imgur.com/7elmg.png

The code

The view

<form [formGroup]="newTaskForm" (submit)="createNewTask()">
   <div class="form-group">
      <label for="name">Name</label>
      <input type="text" name="name" required>
   </div>
   <button type="submit" class="btn btn-default">Submit</button>
</form>

The controller

import { Component } from '@angular/core';
import { FormGroup, FormControl, Validators, FormBuilder }  from '@angular/forms';
import {FormsModule,ReactiveFormsModule} from '@angular/forms';
import { Task } from './task';

@Component({
    selector: 'task-add',
    templateUrl: 'app/task-add.component.html'

})
export class TaskAddComponent {

    newTaskForm: FormGroup;

    constructor(fb: FormBuilder)
    {
        this.newTaskForm = fb.group({
            name: ["", Validators.required]
        });
    }

    createNewTask()
    {
        console.log(this.newTaskForm.value)
    }
}

The ngModule

import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule }   from '@angular/forms';

import { routing }        from './app.routing';
import { AppComponent }  from './app.component';
import { TaskService } from './task.service'

@NgModule({
    imports: [
        BrowserModule,
        routing,
        FormsModule
    ],
    declarations: [ AppComponent ],
    providers: [
        TaskService
    ],
    bootstrap: [ AppComponent ]
})
export class AppModule { }

The question

Why am I getting that error? Am I missing something?

Make sure that you import the ReactiveFormsModule to the module you use forms with ( for instance auth.module , form.module ) not the app.module . angular.io/guide/reactive-forms
I wish I could downvote the Angular team for making the design decisions they made
I occasionally get this error message in VS Code, although my code is correct. I just have to open the xxx.module.ts file and the problems go away immediately. Maybe someone else have the same problem...might be a bug which will be fixed in the future.
None of the answers below solved my problem. my problem was not adding my component to module declarations. So add your component to app.module.ts declarations: [YourComponent]

L
Liam

RC6/RC7/Final release FIX

To fix this error, you just need to import ReactiveFormsModule from @angular/forms in your module. Here's the example of a basic module with ReactiveFormsModule import:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { AppComponent }  from './app.component';

@NgModule({
    imports: [
        BrowserModule,
        FormsModule,
        ReactiveFormsModule
    ],
    declarations: [
        AppComponent
    ],
    bootstrap: [AppComponent]
})

export class AppModule { }

To explain further, formGroup is a selector for directive named FormGroupDirective that is a part of ReactiveFormsModule, hence the need to import it. It is used to bind an existing FormGroup to a DOM element. You can read more about it on Angular's official docs page.

RC5 FIX

You need to import { REACTIVE_FORM_DIRECTIVES } from '@angular/forms' in your controller and add it to directives in @Component. That will fix the problem.

After you fix that, you will probably get another error because you didn't add formControlName="name" to your input in form.


What I don't get is why one needs to add REACTIVE_FORM_DIRECTIVES if FormsModule is being imported inside app.module. The whole point of modules is to avoid having to declare directives inside components.
@DanielPliscki You are completely right, I just found out they fixed this problem in RC6 version that was released today. Now you don't need to do this, you only need to import FormsModule and ReactiveFormsModule. I will edit my answer.
I LOST AN HOUR completing forgetting that I created a separate module for my login form in order to lazy load with modules between states. (I am new to A2, still prefer A1) Please make sure you use the right module! Don't be a schmuck like me. You also no longer need to add to the component. The imports in your module suffice. Thanks
Thanks, worked for me. I am confused why this is not mentioned in the guides for FormControls in Angular 2 that I have stumbled upon..
In Angular 4 I added ReactiveFormsModule in the provider list and it worked. Not sure if this is the way you are supposed to do it though.
S
Sahil

Angular 4 in combination with feature modules (if you are for instance using a shared-module) requires you to also export the ReactiveFormsModule to work.

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';

@NgModule({
  imports:      [
    CommonModule,
    ReactiveFormsModule
  ],
  declarations: [],
  exports: [
    CommonModule,
    FormsModule,
    ReactiveFormsModule
  ]
})
export class SharedModule { } 

C
Ciarán Bruen

Ok after some digging I found a solution for "Can't bind to 'formGroup' since it isn't a known property of 'form'."

For my case, I've been using multiple modules files, i added ReactiveFormsModule in app.module.ts

 import { FormsModule, ReactiveFormsModule } from '@angular/forms';`

@NgModule({
  declarations: [
    AppComponent,
  ]
  imports: [
    FormsModule,
    ReactiveFormsModule,
    AuthorModule,
],
...

But this wasn't working when I use a [formGroup] directive from a component added in another module, e.g. using [formGroup] in author.component.ts which is subscribed in author.module.ts file:

import { NgModule }       from '@angular/core';
import { CommonModule }   from '@angular/common';
import { AuthorComponent } from './author.component';

@NgModule({
  imports: [
    CommonModule,
  ],
  declarations: [
    AuthorComponent,
  ],
  providers: [...]
})

export class AuthorModule {}

I thought if i added ReactiveFormsModule in app.module.ts, by default ReactiveFormsModule would be inherited by all its children modules like author.module in this case... (wrong!). I needed to import ReactiveFormsModule in author.module.ts in order to make all directives to work:

...
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
...

@NgModule({
  imports: [
    ...,
    FormsModule,    //added here too
    ReactiveFormsModule //added here too
  ],
  declarations: [...],
  providers: [...]
})

export class AuthorModule {}

So, if you are using submodules, make sure to import ReactiveFormsModule in each submodule file. Hope this helps anyone.


Works for me, exactly the same problem, I really thought modules in exports array will be inherited by children modules... Don't know why exactly ! EDIT : documentation says exports is to make components, pipes, directives available in the TEMPLATE of any COMPONENT ()
This is the solution if you use lazy loading or work with multiple modules. Thanks.
x
xuhcc

I have encountered this error during unit testing of a component (only during testing, within application it worked normally). The solution is to import ReactiveFormsModule in .spec.ts file:

// Import module
import { ReactiveFormsModule } from '@angular/forms';

describe('MyComponent', () => {
    beforeEach(async(() => {
        TestBed.configureTestingModule({
            declarations: [MyComponent],
            imports: [ReactiveFormsModule],  // Also add it to 'imports' array
        })
        .compileComponents();
    }));
});

s
str

The suggested answer did not work for me with Angular 4. Instead I had to use another way of attribute binding with the attr prefix:

<element [attr.attribute-to-bind]="someValue">

Hey man! Are you sure your answer is related to the question? :) The question was about an issue setting up a form - cause by not properly setting up the ngModule
@johnnyfittizio Pretty sure. Same scenario, same error message.
This worked for me, but is strange - why do I need the attr. ?
Thanks a ton. This worked for me also, but I would think there must be something else triggering the problem, like library versioning, or
tag positioning? Strange.
Found it- the problem was that I needed to import ReactiveFormsModule directly into my page's .module.ts. Not the .page.ts... once I did that, my template could correctly identify the formGroup attribute, without the attr. prefix.
P
Peter Mortensen

The error says that FormGroup is not recognized in this module. So you have to import these (below) modules in every module that uses FormGroup

import { FormsModule, ReactiveFormsModule } from '@angular/forms';

Then add FormsModule and ReactiveFormsModule into your Module's imports array.

imports: [
  FormsModule,
  ReactiveFormsModule
],

You may be thinking that I have already added it in AppModule and it should inherit from it? But it is not. Because these modules are exporting required directives that are available only in importing modules. Read more in Sharing modules.

Other factors for these errors may be be a spelling error like below...

[FormGroup]="form" Capital F instead of small f

[formsGroup]="form" Extra s after form


Great answer! I was missing out on a vital import.
s
sudheer nunna

If you have to import two modules then add like this below

import {ReactiveFormsModule,FormsModule} from '@angular/forms';
@NgModule({
  declarations: [
    AppComponent,
    HomeComponentComponent,
    BlogComponentComponent,
    ContactComponentComponent,
    HeaderComponentComponent,
    FooterComponentComponent,
    RegisterComponent,
    LoginComponent
  ],
  imports: [
    BrowserModule,
    FormsModule,
    HttpModule,
    routes,
    ReactiveFormsModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})

P
Peter Mortensen

Firstly, it is not related to Angular versions>2. Just import the following in your app.module.ts file will fix the problems.

import { FormsModule, ReactiveFormsModule } from '@angular/forms';

Then add FormsModule and ReactiveFormsModule into your imports array.

imports: [
  FormsModule,
  ReactiveFormsModule
],

Note: You can also import ReactiveFormsModule to a specific module instead to app.module.ts


I
Ian Griffin

Keep in mind that if you have defined "Feature Modules", you'll need to import in the Feature Module, even if you already imported to the AppModule. From the Angular documentation:

Modules don't inherit access to the components, directives, or pipes that are declared in other modules. What AppModule imports is irrelevant to ContactModule and vice versa. Before ContactComponent can bind with [(ngModel)], its ContactModule must import FormsModule.

https://angular.io/docs/ts/latest/guide/ngmodule.html


thank you so much! I was working for hours on this issue, can't imagine what the problem was... Simply importing my feature Module to app Module fixed the issue.
C
Chamila Maddumage

I had the same issue with Angular 7. Just import following in your app.module.ts file.

import { FormsModule, ReactiveFormsModule } from '@angular/forms';

Then add FormsModule and ReactiveFormsModule in to your imports array.

imports: [
  FormsModule,
  ReactiveFormsModule
],

S
Saurav

This problem occurs due to missing import of FormsModule,ReactiveFormsModule .I also came with same problem. My case was diff. as i was working with modules.So i missed above imports in my parent modules though i had imported it into child modules,it wasn't working.

Then i imported it into my parent modules as below, and it worked!

import { ReactiveFormsModule,FormsModule  } from '@angular/forms';
import { AlertModule } from 'ngx-bootstrap';

         @NgModule({
          imports: [
            CommonModule,
            FormsModule,
            ReactiveFormsModule,
    ],
      declarations: [MyComponent]
    })

L
Lonely

Your Angular version is 11+, and you use VisualStudioCode? And you have already imported FormsModule, ReactiveFormsModule and added it into your imports-section within e.g. app.module.ts (relevant module can be different, choose the right one):

// app.module.ts (excerpt)
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
imports: [
  ...
  FormsModule,
  ReactiveFormsModule,
  ...
],

You have the right imports (sometimes there are other libs with similar names); you have defined and initialized your form in your component?

// MyWonderfulComponent (excerpt)


import { FormBuilder, FormGroup, Validators } from '@angular/forms';

export class MyWonderfulComponent implements OnInit {
  form: FormGroup; 
  ...
  constructor (private fb: FormBuilder) {
    this.form = this.fb.group({
      // DON'T FORGET THE FORM INITIALISATION
    });
  }

Your Component-Template has your form:

<form [formGroup]="form" (ngSubmit)="submit()">
  <!-- MY FORM CONTROLS ARE ALREADY HERE --> 
</form>

And you still get the error message "...since it isn't a known property of..." ?

then just simple restart your VisualStudioCode :)


Note that you need to import FormsModule/ReactiveFormsModule in the module that the component is actually a part of. Blindly putting those in app.module.ts is not enough.
This solution also worked for me in PhpStorm. After a restart it didn't give the warning anymore.
P
Peter Mortensen

Don't be a dumb dumb like me. I was getting the same error as above, and none of the options in previous answers worked. Then I realized I capitalized 'F' in FormGroup. Doh!

Instead of:

[FormGroup]="form"

Do:

[formGroup]="form"

M
Mr Giggles

I was coming across this error when trying to do e2e testing and it was driving me crazy that there were no answers to this.

IF YOU ARE DOING TESTING, find your *.specs.ts file and add :

import {ReactiveFormsModule, FormsModule} from '@angular/forms';

G
GKooij

For people strolling these threads about this error. In my case I had a shared module where I only exported the FormsModule and ReactiveFormsModule and forgot to import it. This caused a strange error that formgroups were not working in sub components. Hope this helps people scratching their heads.


P
Peter Mortensen

If you have this problem when you are developing a component, you should add these two modules to your closest module:

import { FormsModule, ReactiveFormsModule } from '@angular/forms';
@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
   // other modules
    FormsModule,
    ReactiveFormsModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

And if you are developing a test for your components so you should add this module to your test file like this:

import { async, ComponentFixture, TestBed } from '@angular/core/testing';
import { ContactusComponent } from './contactus.component';
import { ReactiveFormsModule } from '@angular/forms';

describe('ContactusComponent', () => {
  let component: ContactusComponent;
  let fixture: ComponentFixture<ContactusComponent>;

  beforeEach(async(() => {
    TestBed.configureTestingModule({
      declarations: [ContactusComponent],
      imports:[
        ReactiveFormsModule
      ]

    })
      .compileComponents();
  }));

  beforeEach(() => {
    fixture = TestBed.createComponent(ContactusComponent);
    component = fixture.componentInstance;
    fixture.detectChanges();
  });

  it('should create', () => {
    expect(component).toBeTruthy();
  });
});

P
Peter Mortensen

Simple solution:

Step 1: Import ReactiveFormModule

import {ReactiveFormsModule} from '@angular/forms';

Step 2: Add "ReactiveFormsModule" to the import section

imports: [

    ReactiveFormsModule
  ]

Step 3: Restart the application and done

Example:

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import {ReactiveFormsModule} from '@angular/forms';
import { EscalationManagementRoutingModule } from './escalation-management-routing.module';
import { EscalationManagementRouteWrapperComponent } from './escalation-management-route-wrapper.component';


@NgModule({
  declarations: [EscalationManagementRouteWrapperComponent],
  imports: [
    CommonModule,
    EscalationManagementRoutingModule,
    ReactiveFormsModule
  ]
})
export class EscalationManagementModule { }

P
Peter Højlund Palluth

A LITTLE NOTE: Be careful about loaders and minimize (Rails env.):

After seeing this error and trying every solution out there, i realised there was something wrong with my html loader.

I've set my Rails environment up to import HTML paths for my components successfully with this loader (config/loaders/html.js.):

module.exports = {
  test: /\.html$/,
  use: [ {
    loader: 'html-loader?exportAsEs6Default',
    options: {
      minimize: true
    }
  }]
}

After some hours efforts and countless of ReactiveFormsModule imports i saw that my formGroup was small letters: formgroup.

This led me to the loader and the fact that it downcased my HTML on minimize.

After changing the options, everything worked as it should, and i could go back to crying again.

I know that this is not an answer to the question, but for future Rails visitors (and other with custom loaders) i think this could be helpfull.


Thanks for this, i finally had to use => minimize: {caseSensitive: true} to get it working
D
DIBYA RANJAN TRIPATHY

Import and register ReactiveFormsModule in your app.module.ts.

import { ReactiveFormsModule } from '@angular/forms';

@NgModule({
declarations: [
AppComponent,
HighlightDirective,
TestPipeComponent,
ExpoentialStrengthPipe

],
imports: [
BrowserModule,
ReactiveFormsModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }

Make sure your spelling is correct in both .ts and .html file. xxx.ts

  profileForm = new FormGroup({
  firstName: new FormControl(''),
 lastName: new FormControl('')
 });

xxx.html file-

  <form [formGroup]="profileForm"> 
  <label>
  First Name:
   <input type="text" formControlName = "firstName">
  </label>

  <label>
  Last Name:
   <input type="text" formControlName = "lastName">
   </label>
   </form>

I was by mistake wrote [FormGroup] insted of [formGroup]. Check your spelling correctly in .html. It doesn't throw compile time error If anything wrong in .html file.


L
Leelavathi Ravindran

The ReactiveFormsModule and FormsModule import should be added in your custom component module and also its parent component from where it is getting called.

For example, I needed to add form for my filter component. So I should add this import in my filter module and its parent page (might be list) module from where this filter button gets clicked.


M
Mounir bkr

go to: app.module.ts imports:[ .... ReactiveFormsModule ] add this: import { ReactiveFormsModule } from '@angular/forms'; it should look like that:

import {MatRadioModule} from '@angular/material/radio'; @NgModule({ declarations: [ ], imports: [ ReactiveFormsModule ], providers: [], bootstrap: [AppComponent] }) export class AppModule { }


n
nik7

Note: if you are working inside child module's component, then you just have to import ReactiveFormsModule in child module rather than parent app root module.


This was the magic sauce that was missing for me.
m
manjeet lama

I tried almost all the solution here but my problem was a little different(stupid). I added the component in routing module but didn't include it main module. So make sure your component is part of the module.


If your component is a child component, don't forget to add import { FormsModule, ReactiveFormsModule } from '@angular/forms'; to its respective module.
P
Peter Mortensen

Using and import REACTIVE_FORM_DIRECTIVES:

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';
import { AppComponent }  from './app.component';

@NgModule({
    imports: [
        BrowserModule,
        FormsModule,
        ReactiveFormsModule
    ],
    declarations: [
        AppComponent
    ],
    bootstrap: [AppComponent]
})

export class AppModule { }

Is "REACTIVE_FORM_DIRECTIVES" literal?
P
Peter Mortensen

Import ReactiveFormsModule in the corresponding module.


P
Peter Mortensen

If this is just a TypeScript error but everything on your form works, you may just have to restart your IDE.


P
Peter Mortensen

I had the same problem. Make sure that if using submodules (for example, you not only have app.component.module.ts), but you have a separate component such as login.module.ts, that you include ReactiveFormsModule import in this login.module.ts import, for it to work. I don't even have to import ReactiveFormsModule in my app.component.module, because I'm using submodules for everything.

File login.module.ts

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';

import { IonicModule } from '@ionic/angular';

import { LoginPageRoutingModule } from './login-routing.module';

import { LoginPage } from './login.page';

@NgModule({
  imports: [
    CommonModule,
    FormsModule,
    ReactiveFormsModule,
    IonicModule,
    LoginPageRoutingModule
  ],
  declarations: [LoginPage]
})
export class LoginPageModule {}

that was also a problem in my case. I had enter-credentials-modal-component and login-site-component. it did not work until I did import of FormsModule and ReactiveFormsModule for both of them
P
Peter Mortensen

When you have a formGroup in a modal (entrycomponent), then you have to import ReactiveFormsModule also in the module where the modal is instantiated.


G
Gyanswarup Mohanty

import { FormsModule, ReactiveFormsModule } from '@angular/forms'; and add it in imports array in the app-module.ts file.


T
Trevor

You can get this error message even if you have already imported FormsModule and ReactiveFormsModule. I moved a component (that uses the [formGroup] directive) from one project to another, but failed to add the component to the declarations array in the new module. That resulted in the Can't bind to 'formGroup' since it isn't a known property of 'form' error message.


have you tried to reload the project with an ng serve after the modification? (if you have embedded modules, you must import the form ans reactive form modules in each and every module using formGroup)