angular - How to detect async change to ng-content

Question

I made a component which uses the marked package to render markdown content, the thing is it doesn't re-render itself when an async event changes its ng-content element.

Here's the code

import {Component, ElementRef, AfterContentInit} from 'angular2/core';
declare var marked: any;

@Component({
    selector: 'markdown',
    template:
    '<div style="display:none;">' +
    '    <ng-content></ng-content>' +
    '</div>' +
    '<div class="markdown" [innerHTML]="output"></div>'
})
export class MarkdownComponent implements AfterContentInit {
    output: string;

    constructor(
        private element: ElementRef) {
    }

    ngAfterContentInit() {
        const c = this.element.nativeElement.childNodes;
        this.output = marked(c[0].textContent);
    }
}

Here's the HTML snippet:

<markdown>{{info}}</markdown>

And here's the async update:

updateInfo(text: string) {
    this.svc.update(this.info, text).subscribe(
        data => this.info = data.newText);
}

The problem is, when the this.svc.update event fires, the info variable changes value, but the markdown component doesn't get re-rendered.

Thanks!

RESOLUTION

Following the accepted answer's advice (thanks Gunter), here's the new component, it's leaner and simpler:

import {Component} from 'angular2/core';
declare var marked: any;

@Component({
    selector: 'markdown',
    template: '<div class="markdown" [innerHTML]="process(md)"></div>',
    inputs: ['md']
})
export class MarkdownComponent {
    md: string;

    process(s: string) {
        if (!s) return '';
        return marked(s);
    }
}

And here's the new HTML:

<markdown [md]="info"></markdown>

Works perfectly! :)

Answer 1

Even if the Günter's answer is great, I wasn't able to resist to create a little plunkr describing how to use Marked into a component: https://plnkr.co/edit/0oSeaIyMWoq5fAKKlJLA?p=preview.

Here are the details:

• Marked configuration the HTML file

  <script>
    System.config({
      transpiler: 'typescript', 
      typescriptOptions: { emitDecoratorMetadata: true }, 
      packages: {
        'src': {defaultExtension: 'ts'}
      },
      map: {
        marked: 'https://cdnjs.cloudflare.com/ajax/libs/marked/0.3.5/marked.js'
      }
    });
    System.import('src/boot')
      .then(null, console.error.bind(console));
  </script>
  

• The component that uses Marked

  import { Component, Input } from 'angular2/core';
  import marked from 'marked';
  
  @Component({
    selector: 'markdown', 
    template: `
      <div [innerHTML]="convertedData"></div>
    `
  })
  export class MarkdownComponent {
    @Input('data')
    data:string;
  
    ngOnChanges() { 
      this.convertedData = marked(this.data);
    }
  }
  

• The component that uses the previous Markdown component

  import { Component } from 'angular2/core';
  import { MarkdownComponent } from './markdown';
  
  @Component({
    selector: 'my-app', 
    template: `
      <div>
        <markdown [data]="markdown"></markdown>
      </div>
    `,
    directives: [ MarkdownComponent ]
  })
  export class AppComponent {
    constructor() {
      this.markdown = 'Hello';
  
      setTimeout(() => {
        this.markdown = `
  # Title
  
  Some __test__
  `;
      }, 1000);
    }
  }