无法绑定到“formControl”，因为它不是“输入”的已知属性 - Angular2 Material Autocomplete 问题

Question

我正在尝试在我的 Angular 2 项目中使用 Angular Material Autocomplete 组件。我在模板中添加了以下内容。

<md-input-container>
   <input mdInput placeholder="Category" [mdAutocomplete]="auto" [formControl]="stateCtrl">
</md-input-container>

<md-autocomplete #auto="mdAutocomplete">
   <md-option *ngFor="let state of filteredStates | async" [value]="state">
      {{ state }}
   </md-option>
</md-autocomplete>

以下是我的组件。

import {Component, OnInit} from "@angular/core";
import {ActivatedRoute, Router} from "@angular/router";
import {FormControl} from "@angular/forms";

@Component({
    templateUrl: './edit_item.component.html',
    styleUrls: ['./edit_item.component.scss']
})
export class EditItemComponent implements OnInit {
    stateCtrl: FormControl;
    states = [....some data....];

    constructor(private route: ActivatedRoute, private router: Router) {
        this.stateCtrl = new FormControl();
        this.filteredStates = this.stateCtrl.valueChanges.startWith(null).map(name => this.filterStates(name));
    }
    ngOnInit(): void {
    }
    filterStates(val: string) {
        return val ? this.states.filter((s) => new RegExp(val, 'gi').test(s)) : this.states;
    }
}

我收到以下错误。似乎找不到 formControl 指令。

无法绑定到“formControl”，因为它不是“输入”的已知属性

这里有什么问题？

Answer 1

在使用formControl 时，您必须将ReactiveFormsModule 导入到您的imports 数组中。

例子：

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

@NgModule({
  imports: [
    BrowserModule,
    FormsModule,
    ReactiveFormsModule,
    MaterialModule,
  ],
  ...
})
export class AppModule {}

Answer 2

忘记尝试破译示例 .ts - 正如其他人所说，它通常不完整。

只需单击此处圈出的“弹出”图标，您将获得fully working StackBlitz example。

您可以快速确认所需的模块：

注释掉ReactiveFormsModule的任何实例，果然你会得到错误：

Template parse errors:
Can't bind to 'formControl' since it isn't a known property of 'input'. 

Answer 3

发生这种情况的另一个原因：

您在其中使用formControl 的组件未在导入ReactiveFormsModule 的模块中声明。

因此请检查声明引发此错误的组件的模块。

Answer 4

从 9.1.4 版本开始你只需要导入ReactiveFormsModule

https://angular.io/guide/reactive-forms

Answer 5

在 Angular 12 中，matautocompleteModule 的导入路径发生了变化，它 解决了我的问题....现在看起来像这样

Answer 6

首先将常规 matInput 添加到您的模板中。假设您正在使用 ReactiveFormsModule 中的 formControl 指令来跟踪输入的值。

反应式表单提供了一种模型驱动的方法来处理值随时间变化的表单输入。本指南向您展示如何创建和更新简单的表单控件、如何在组中使用多个控件、验证表单值以及实现更高级的表单。

import { FormsModule, ReactiveFormsModule } from "@angular/forms"; //this to use ngModule

...

imports: [
    BrowserModule,
    AppRoutingModule,
    HttpModule,
    FormsModule,
    RouterModule,
    ReactiveFormsModule,
    BrowserAnimationsModule,
    MaterialModule],

Answer 7

嗯，对我有用的是在@component({}) 中的模板`` 中构建表单，例如--

import { Component, OnInit } from '@angular/core';
import { FormControl } from '@angular/forms';

@Component({
  selector: 'app-contact-form',
  template:`
  <form class="validation-form" validate method="createUserWithEmailAndPassword">
  <div class="form-row">
    <div class="col-md-6 mb-3">
      <label for="firstName">First name</label>
      <input type="text" [formControl]="firstName" id="firstName" placeholder="Please enter your first name" required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-6 mb-3">
      <label for="lastName">Last name</label>
      <input type="text" [formControl]="lastName" id="lastName" placeholder="Please enter your last name" required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
  </div>
    <div class="form-row">
      <div class="col-md-6 mb-3">
        <label for="email">Email address</label>
        <input type="email" [formControl]="email" id="email" aria-describedby="emailHelp" placeholder="Please enter your last name" required>
        <small id="emailHelp" class="form-text text-muted">We'll never share your email with anyone else.</small>
        <div class="valid-feedback">
          Looks good!
        </div>
      </div>
    </div>
    <div class="col-md-6 mb-3">
      <label for="password">Password</label>
      <input type="password" [formControl]="password" id="password" placeholder="Please enter your password" required>
      <div class="valid-feedback">
        Looks good!
      </div>
    </div>
    <div class="col-md-3 mb-3">
      <label for="zip">Zip</label>
      <input type="text" [formControl]="zip" id="zip" required>
      <div class="invalid-feedback">
        Please provide a valid zip.
      </div>
    </div>
  </div>
  <div class="form-group">
    <div class="form-check">
      <input class="form-check-input" type="checkbox" value="" id="invalidCheck" required>
      <label class="form-check-label" for="invalidCheck">
        Agree to terms and conditions
      </label>
      <div class="invalid-feedback">
        You must agree before submitting.
      </div>
    </div>
  </div>
  <button class="btn btn-primary" type="submit">Submit form</button>
</form>`,

  templateUrl: './contact-form.component.html',
  styleUrls: ['./contact-form.component.scss']
})
export class ContactFormComponent implements OnInit {

  firstName =  new FormControl('');
  lastName =  new FormControl('');
  email =  new FormControl('');
  password =  new FormControl('');

  constructor() { }

  ngOnInit(): void {
  }

}

这停止显示错误。如果错误仍然存​​在，那么这可能对您有用