Issue passing value into Angular 2 component [duplicate]

问题

I am trying to pass a simple string into an angular 2 component. For the life of me I can't find the issue. I am passing the value in as a hardcoded value on the component from index.html

<html>
  <head>
    <title>Angular 2 QuickStart</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="styles.css">

    <!-- 1. Load libraries -->
     <!-- Polyfill(s) for older browsers -->
    <script src="node_modules/es6-shim/es6-shim.min.js"></script>

    <script src="node_modules/zone.js/dist/zone.js"></script>
    <script src="node_modules/reflect-metadata/Reflect.js"></script>
    <script src="node_modules/systemjs/dist/system.src.js"></script>

    <!-- 2. Configure SystemJS -->
    <script src="systemjs.config.js"></script>
    <script>
      System.import('app').catch(function(err){ console.error(err);  });
    </script>
  </head>

  <!-- 3. Display the application -->
  <body>


    <accordian [inputField]="'string'">Loading...</accordian>


  </body>
</html>

Component

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

@Component({
  selector: 'accordian',
  templateUrl: 'app/accordian.html',
  styleUrls:  ['app/accordian.css']
})
export class Accordian {
  @Input() inputField;
  expanded = true;
  expandToggle(){
    console.log(this.inputField)
    this.expanded = !this.expanded;
  }
}

Template

<header (click)="expandToggle($event)">
  <h4>Select an Activity!!!</h4>
  <button>{{expanded ? '-' : '+'}}</button>
</header>
<ul *ngIf="expanded">
  <li>
      <h5>{{inputField}}</h5>
      <a href="#">Update Personal Information</a>
  </li>
  <li>
      <h5>User Tools</h5>
      <a href="#">Update Personal Information</a>
  </li>
  <li>
      <h5>User Tools</h5>
      <a href="#">Update Personal Information</a>
  </li>
</ul>

All I get is undefined when I click on the plus button to spit out the value. Any help would be fantastic!

回答1:

Angular doesn't do any binding from index.html only from within other components.

A workaround to get attribute values in the root component is

export class AppComponent {
  constructor(elementRef:ElementRef) {
    console.log(elementRef.nativeElement.getAttribute('inputField));
  }
}

See also https://github.com/angular/angular/issues/1858

回答2:

I am not sure you can do this from index.html

Usually to use Components (or Directives) you need to specify them as directives with the @Component or @Directive decorators.

I should start with the standard AppComponent approach of the QuickStart and use Accordian within AppComponent.

I hope this helps.

回答3:

Here is the link to working plunker code

Index.html

<!DOCTYPE html>
<html>

  <head>
    <title>angular2 playground</title>
    <link rel="stylesheet" href="style.css" />
    <script src="https://code.angularjs.org/2.0.0-beta.17/angular2-polyfills.js"></script>
    <script src="https://code.angularjs.org/tools/system.js"></script>
    <script src="https://code.angularjs.org/tools/typescript.js"></script>
    <script src="config.js"></script>
    <script>
    System.import('app')
      .catch(console.error.bind(console));
  </script>
  </head>

  <body>
    <my-app>
    loading...
  </my-app>
  </body>

</html>

main.ts

import {bootstrap} from '@angular/platform-browser-dynamic';
import {App} from './app';

bootstrap(App, [])
  .catch(err => console.error(err));

app.ts

import {Component} from '@angular/core';
import {Accordian} from './accordian';

@Component({
  selector: 'my-app',
  providers: [],
  template: `
    <div>
      <accordian [inputField]='"string"'></accordian>
    </div>
  `,
  directives: [Accordian]
})
export class App {
  constructor() {
    this.name = 'Angular2 (Release Candidate!)'
  }
}

accordian.ts

import {Component, Input} from '@angular/core'

@Component({
  selector: 'accordian',
  providers: [],
  template: `
    <header (click)="expandToggle($event)">
      <h4>Select an Activity!!!</h4>
      <button>{{expanded ? '-' : '+'}}</button>
    </header>
    <ul *ngIf="expanded">
      <li>
          <h5>{{inputField}}</h5>
          <a href="#">Update Personal Information</a>
      </li>
      <li>
          <h5>User Tools</h5>
          <a href="#">Update Personal Information</a>
      </li>
      <li>
          <h5>User Tools</h5>
          <a href="#">Update Personal Information</a>
      </li>
    </ul>
  `,
  directives: []
})
export class Accordian {
  @Input() inputField: string;
  expanded = true;

  expandToggle(){
    console.log(this.inputField)
    this.expanded = !this.expanded;
  }

}

来源：https://stackoverflow.com/questions/37149618/issue-passing-value-into-angular-2-component

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