Angular 6: Can't bind to 'formGroup' since it isn't a known property of 'form'?

问题

I have worked with form builder in angular 2/4, But now I am using it in angular 6. I have seen this question (Can't bind to 'formGroup' since it isn't a known property of 'form') but it was for angular 2. I doing exact same against angular 4 but I am getting this error. Please help: my code are:

app.module.ts: ( I have exported FormsModule & ReactiveFormsModule) :

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { LocalStorage } from './services/localStorage.service';
import { HttpModule, RequestOptions, XHRBackend } from '@angular/http';
import { Router } from '@angular/router';
import { RouterModule } from '@angular/router';
import { AppComponent } from './app.component';
import { routing } from './app.route';

import { FormsModule, ReactiveFormsModule }         from '@angular/forms';
import { LoginComponent } from './components/login/component';
import { ForgotComponent } from './components/forgotPassword/component';


@NgModule({
  exports: [
    FormsModule,
    ReactiveFormsModule
  ],
  declarations: [
    AppComponent,LoginComponent,ForgotComponent
  ],
  imports: [
    BrowserModule,
    routing,

  ],
  providers: [
    LocalStorage,
  ],
  bootstrap: [AppComponent],

})
export class AppModule { }

login.component.ts:

import { Component, ViewContainerRef, OnInit } from '@angular/core';
import { Router } from '@angular/router';
import { FormBuilder, FormGroup, Validators, NgForm } from '@angular/forms';
import { LocalStorage } from '../../services/localStorage.service';
import { environment } from '../../../environments/environment';
import { HttpService } from '../../services/http.service';
import { emailRegexp, passwordRegexp } from '../../constants';
@Component({
    selector: 'login-app',
    templateUrl: './login.component.html',
    styleUrls: ['./login.component.scss']
})

/**
 * LoginComponent class
 */

export class LoginComponent {
    private loginForm: any;
    loginValue:any;

    constructor(
        private formBuilder: FormBuilder,
        private _router: Router,
        private httpService: HttpService,
        private localStorage: LocalStorage,
    ) {
        this.loginValue = new LocalStorage(environment.localStorageKeys.ADMIN).value;

        this.loginForm = this.formBuilder.group({
            email: ['', Validators.compose([Validators.required, Validators.pattern(emailRegexp)])],
            password: ['', Validators.compose([Validators.required, Validators.minLength(8)])]
        });
    }
}

login.component.html: ( Something like this)

 <form [formGroup]="loginForm" (ngSubmit)="loginForm.valid && login()" novalidate>

 <input type="email" autocomplete="off" (focus)="focusFunction()" placeholder="User Name" formControlName="email" class="form-control">

<div class="col-12">
 <input autocomplete="off" type="password" (focus)="focusFunction()" placeholder="Password" formControlName="password" class="form-control">
 </div>

 <button [disabled]="!loginForm.valid" type="submit" class="btn btn-inverse btn-rounded btn-block">
            <div  *ngIf="!loading" class="sign-in">Sign in</div>
  </button>

  </form>

回答1:

Add below code in your app.module.ts:

import { BrowserModule } from '@angular/platform-browser';
import { FormsModule, ReactiveFormsModule } from '@angular/forms';

and in imports array:

imports: [
        BrowserModule,
        FormsModule,
        ReactiveFormsModule
    ]

The FormGroup is a selector for the FormGroupDirective Directive which mainly used to Binds an existing FormGroup to a DOM element and FormGroupDirective is available in the ReactiveFormsModule module.

回答2:

So fiddling around with the same frustrating issue -- a clean angular-cli install and a custom subcomponent/module (component.html... ) and the same error ("Can't bind to 'formGroup' since it isn't a known property of 'form' "). Angular CLI: 7.2.3, Node: 10.9.0, OS: win32 x64, Angular: 7.2.2

I finally got it to work based on the above but with a twist I put the FormsModule & ReactiveFormsModule imports in app-routing.module.ts (not app.module.ts) + the subcomponent's ts (in my case: forms-demo.component.ts) :

import { FormsModule, ReactiveFormsModule } from '@angular/forms';
....
@NgModule({
  imports: [
    RouterModule.forRoot(routes), 
    FormsModule, ReactiveFormsModule
....

Afterward ng build/serve worked without any errors.

I'm not an Angular expert but my guess is that the v7 approach whereby app.module.ts delegates to app-routing, that latter file is where the app & component imports & dependencies take place.... YMMV but hopefully it helps.

回答3:

import these things in your appmodule.ts

imports: [
        BrowserModule,
        FormsModule,
        ReactiveFormsModule
    ],

回答4:

Update app.module.ts as follows in belows diff

来源：https://stackoverflow.com/questions/50964204/angular-6-cant-bind-to-formgroup-since-it-isnt-a-known-property-of-form