Angular 2：无法绑定到“ng model”，因为它不是“input”的已知属性

Question

我试图在Angular 2中实现动态表单。我在动态表单中添加了删除和取消等附加功能。我遵循了以下文档：https://angular.io/docs/ts/latest/cookbook/dynamic-form.html

我对代码做了一些修改。我在这里搞错了。

我如何使这个错误消失？

您可以在这里找到完整的代码:http://plnkr.co/edit/sl949g1hqqrnrur1xxqt?p=preview，它在plunker中工作，但在我的本地系统中不工作。

Html代码：

<div>
  <form [formGroup]="form">

    <div *ngFor="let question of questions" class="form-row">
      <label [attr.for]="question.key">{{question.label}}</label>

  <div [ngSwitch]="question.controlType">

    <input *ngSwitchCase="'textbox'" [formControlName]="question.key"
            [id]="question.key" [type]="question.type" [(ngModel)]="question.value">

    <select [id]="question.key" [(ngModel)]="question.value" *ngSwitchCase="'dropdown'" [formControlName]="question.key" >
      <option *ngFor="let opt of question.options" [ngValue]="opt.key" >{{opt.value}}</option>
    </select>

    <input *ngSwitchCase="'checkbox'"  [(ngModel)]="question.value"
            [id]="question.key" [type]="question.type" (change)="question.value = ck.checked" #ck [ngModelOptions]="{standalone: true}">

  </div> 
  <div class="errorMessage" *ngIf="!form.controls[question.key].valid">{{question.label}} is required</div>
    </div>

    <div class="form-row">
      <button type="submit" [disabled]="!form.valid" (click)="onSubmit()">Save</button>
      <button type="button" class="btn btn-default" (click)="cancel()">Cancel</button>
      <button type="button" class="btn btn-default" (click)="clear()">Clear</button>

    </div>
  </form>

  <div *ngIf="payLoad" class="form-row">
    <strong>Saved the following values</strong><br>{{payLoad}}
  </div>
</div>

组件代码：

import { Component, Input, OnInit }  from '@angular/core';
import { FormGroup, REACTIVE_FORM_DIRECTIVES } from '@angular/forms';
import { QuestionBase }                 from './question-base';
import { QuestionControlService }       from './question-control.service';
import { ControlGroup }     from '@angular/common';
import {ChangeDetectorRef} from '@angular/core';
import { FormsModule }   from '@angular/forms';

@Component({
  selector: 'dynamic-form',
  templateUrl: 'app/dynamicform/form.component.html',
  directives: [REACTIVE_FORM_DIRECTIVES],
  providers:  [QuestionControlService]
})
export class DynamicFormComponent implements OnInit {

  @Input() questions: QuestionBase<any>[] = [];
  form: FormGroup;
  payLoad:any;
  payLoad2:any;
  questiont: QuestionBase<any>;
  questiond: QuestionBase<any>;
  constructor(private qcs: QuestionControlService, private cdr: ChangeDetectorRef) {  }
  ngOnInit() {
    this.form = this.qcs.toFormGroup(this.questions);
    console.log("Form Init",this.questions);
    this.questiont = JSON.parse(JSON.stringify(this.questions));
    this.questiond = JSON.parse(JSON.stringify(this.questions));
  }
  onSubmit() {
    this.payLoad = JSON.stringify(this.form.value);
    this.payLoad2=this.payLoad;
    this.questiont = JSON.parse(JSON.stringify(this.questions));
    console.log("Submitted data",this.questions);
  }
  cancel(){
    console.log("Canceled");
    this.questions = JSON.parse(JSON.stringify(this.questiont));
  }
  clear(){
    this.questions = JSON.parse(JSON.stringify(this.questiond));
    this.questiont = JSON.parse(JSON.stringify(this.questiond));
    console.log("Cleared");
    this.cdr.detectChanges();
  }
}

Answer 1

我在升级到RC5后遇到了类似的错误；即Angular 2：不能绑定到“ng model”，因为它不是“input”的已知属性。

Plunker上的代码显示了使用Angular2 RC4，但https://Angular.io/docs/ts/latest/cookbook/dynamic-form.html上的示例代码使用的是RC5的一部分NGModule。NGModules是从RC4到RC5的一个突破性变化。

本页解释了从RC4到RC5的迁移:https://angular.io/docs/ts/latest/cookbook/rc4-to-rc5.html

我希望这能解决您正在遇到的错误，并帮助您朝着正确的方向前进。

简而言之，我必须在app.module.ts中创建一个NGModule：

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

import { AppComponent }  from './app.component';

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

然后更改main.ts以使用模块：

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { AppModule } from './app.module';

platformBrowserDynamic().bootstrapModule(AppModule);

当然，我还需要更新package.json中的依赖项。下面是我从package.json获得的依赖项。诚然，我从其他来源（可能是ng文档的示例）将它们拼凑在一起，因此您的里程可能会有所不同：

...
"dependencies": {
    "@angular/common": "2.0.0-rc.5",
    "@angular/compiler": "2.0.0-rc.5",
    "@angular/core": "2.0.0-rc.5",
    "@angular/forms": "0.3.0",
    "@angular/http": "2.0.0-rc.5",
    "@angular/platform-browser": "2.0.0-rc.5",
    "@angular/platform-browser-dynamic": "2.0.0-rc.5",
    "@angular/router": "3.0.0-rc.1",
    "@angular/router-deprecated": "2.0.0-rc.2",
    "@angular/upgrade": "2.0.0-rc.5",
    "systemjs": "0.19.27",
    "core-js": "^2.4.0",
    "reflect-metadata": "^0.1.3",
    "rxjs": "5.0.0-beta.6",
    "zone.js": "^0.6.12",
    "angular2-in-memory-web-api": "0.0.15",
    "bootstrap": "^3.3.6"
  },
...

我希望这能更好地帮助你。：-）

Answer 2

为了使ngModel在使用AppModules（NgModule）时工作，您必须在您的AppModule中导入FormsModule。

像这样：

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

import { AppComponent }   from './app.component';


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

Answer 3

找到了一个快速的解决方案，如下所示更新@ngmodule代码：

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

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

export class AppModule { }

源：无法绑定到“ng model”，因为它不是“input”的已知属性