无法绑定到"formGroup"，因为它不是"form"的已知属性 [英] Can't bind to 'formGroup' since it isn't a known property of 'form'

问题描述

情况:

请帮助！我正在尝试使Angular2应用程序中的表单变得非常简单，但是无论它永远无法正常工作.

语言版本:

Angular 2.0.0 Rc5

错误:

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

代码:

视图:

 <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>
 

控制器:

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)
    } 
}

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 { }

问题:

为什么会出现该错误?

我想念什么吗?

解决方案

RC5 FIX

您需要在控制器中import { REACTIVE_FORM_DIRECTIVES } from '@angular/forms'并将其添加到@Component中的directives.这样可以解决问题.

解决此问题后，您可能会遇到另一个错误，因为您没有在表单的输入中添加formControlName="name".

RC6/RC7/最终版本FIX

要解决此错误，您只需从模块中的@angular/forms导入ReactiveFormsModule.这是带有ReactiveFormsModule import的基本模块的示例:

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 { }

为进一步说明，formGroup是名为FormGroupDirective的指令的选择器，该指令是ReactiveFormsModule的一部分，因此需要导入它.它用于将现有的FormGroup绑定到DOM元素.您可以在 Angular的官方文档页面上了解更多相关信息.. >

THE SITUATION:

Please help! I am trying to make what should be a very simple form in my Angular2 app but no matter what it never works.

ANGULAR VERSION:

Angular 2.0.0 Rc5

THE ERROR:

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

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?

解决方案

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.

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.

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