Angular 2 two way binding using ngModel is not working

问题

Can\'t bind to \'ngModel\' since it isn\'t a know property of the \'input\' element and there are no matching directives with a corresponding property

Note: im using alpha.31

import { Component, View, bootstrap } from \'angular2/angular2\'

@Component({
    selector: \'data-bind\'
})
@View({
    template:`
        <input id=\"name\" type=\"text\" 
            [ng-model]=\"name\" 
            (ng-model)=\"name = $event\" />
        {{ name }}
    ` 
})
class DataBinding { 
    name: string;

    constructor(){
        this.name = \'Jose\';
    }
}

bootstrap(DataBinding);

回答1:

Angular has released its final version on 15th of September. Unlike Angular 1 you can use ngModel directive in Angular 2 for two way data binding, but you need write it in a bit different way like [(ngModel)] (Banana in a box syntax). Almost all angular2 core directives doesn't support kebab-case now instead you should use camelCase.

Now ngModel directive belongs to FormsModule, that's why you should import the FormsModule from @angular/forms module inside imports metadata option of AppModule(NgModule). Thereafter you can use ngModel directive inside on your page.

app/app.component.ts

import { Component } from '@angular/core';

@Component({
  selector: 'my-app',
  template: `<h1>My First Angular 2 App</h1>
    <input type="text" [(ngModel)]="myModel"/>
    {{myModel}}
  `
})
export class AppComponent { 
  myModel: any;
}

app/app.module.ts

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 ], //< added FormsModule here
  declarations: [ AppComponent ],
  bootstrap:    [ AppComponent ]
})

export class AppModule { }

app/main.ts

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

const platform = platformBrowserDynamic();
platform.bootstrapModule(AppModule);

Demo Plunkr

回答2:

Key Points:

1. ngModel in angular2 is valid only if the FormsModule is available as a part of your AppModule.

2. ng-model is syntatically wrong.

3. square braces [..] refers to the property binding.
4. circle braces (..) refers to the event binding.
5. when square and circle braces are put together as [(..)] refers two way binding, commonly called banana box.

So, to fix your error.

Step 1: Importing FormsModule

import {FormsModule} from '@angular/forms'

Step 2: Add it to imports array of your AppModule as

imports :[ ... , FormsModule ]

Step 3: Change ng-model as ngModel with banana boxes as

 <input id="name" type="text" [(ngModel)]="name" />

Note: Also, you can handle the two way databinding separately as well as below

<input id="name" type="text" [ngModel]="name" (ngModelChange)="valueChange($event)"/>

valueChange(value){

}

回答3:

As per Angular2 final, you do not even have to import FORM_DIRECTIVES as suggested above by many. However, the syntax has been changed as kebab-case was dropped for the betterment.

Just replace ng-model with ngModel and wrap it in a box of bananas. But you have spilt the code into two files now:

app.ts:

import { Component } from '@angular/core';

@Component({
  selector: 'ng-app',
  template: `
    <input id="name" type="text" [(ngModel)]="name"  />
    {{ name }}
  `
})
export class DataBindingComponent {
  name: string;

  constructor() {
    this.name = 'Jose';
  }
}

app.module.ts:

import { NgModule } from '@angular/core';
import { FormsModule } from '@angular/forms';
import { BrowserModule } from '@angular/platform-browser';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { DataBindingComponent } from './app'; //app.ts above

@NgModule({
  declarations: [DataBindingComponent],
  imports:      [BrowserModule, FormsModule],
  bootstrap:    [DataBindingComponent]
})
export default class MyAppModule {}

platformBrowserDynamic().bootstrapModule(MyAppModule);

回答4:

In the app.module.ts

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

Later in the @NgModule decorator's import:

@NgModule({
imports: [
BrowserModule,
FormsModule
]

})

回答5:

Angular 2 Beta

This answer is for those who use Javascript for angularJS v.2.0 Beta.

To use ngModel in your view you should tell the angular's compiler that you are using a directive called ngModel.

How?

To use ngModel there are two libraries in angular2 Beta, and they are ng.common.FORM_DIRECTIVES and ng.common.NgModel.

Actually ng.common.FORM_DIRECTIVES is nothing but group of directives which are useful when you are creating a form. It includes NgModel directive also.

app.myApp = ng.core.Component({
    selector: 'my-app',
    templateUrl: 'App/Pages/myApp.html',
    directives: [ng.common.NgModel] // specify all your directives here
}).Class({
    constructor: function () {
        this.myVar = {};
        this.myVar.text = "Testing";
    },

});

回答6:

The answer that helped me: The directive [(ngModel)]= not working anymore in rc5

To sum it up: input fields now require property name in the form.

回答7:

instead of ng-model you can use this code:

import { Component } from '@angular/core';

@Component({
  selector: 'my-app',
  template: `<input #box (keyup)="0">
    <p>{{box.value}}</p>`,
})
export class AppComponent  {}

inside your app.component.ts

回答8:

Add below code to following files.

app.component.ts

<input type="text" [(ngModel)]="fname" >
{{fname}}
export class appcomponent {
fname:any;
}

app.module.ts

import {FormsModule} from '@angular/forms';
@NgModule({
imports: [ BrowserModule,FormsModule ],
declarations: [ AppComponent],
bootstrap:    [ AppComponent ]
})

Hope this helps

来源：https://stackoverflow.com/questions/31623879/angular-2-two-way-binding-using-ngmodel-is-not-working