angular 2 - how embed youtube video

Question

I got this code

 <div *ngIf="topic.video">
        <div class="video-container">
            <iframe width="300" height="169" src="topic.video.url" style="border:0"></iframe>
        </div>
    </div>

problem: angular will output src="localhost://8001" instead of src="https://www.youtube.com/embed/hr4BbdUiTUM"

What could be wrong here?

UPDATE 2

This is what got after Gunter's answer.

import { Component, OnInit, Pipe, Sanitizer } from '@angular/core';
import { DataService } from '../../shared/data';

    @Component({
        template: `
            <div class="subheader">Feed</div>
                <div *ngFor="let topic of topics; let index = index; trackBy: trackByFn">
                    <div *ngIf="topic.type == 'discussion'">
                        <div *ngIf="topic.video">
                            <div class="video-container">
                                <iframe src="{{sanitizer.bypassSecurityTrustResourceUrl(topic.video.url)}}" ></iframe>
                            </div>
                        </div>
                </div>
            </div>
        `
    })
    export class CompanyComponent implements OnInit {
        constructor(
            private sanitizer:Sanitizer,
            private dataService: DataService
        ) {}

        ngOnInit() {
            this.topics = this.dataService.topics;
        }
    }

I still got this error

company.ts?ac6a:121 Error: Uncaught (in promise): Error: Error in ./CompanyComponent class CompanyComponent - inline template:29:41 caused by: unsafe value used in a resource URL context (see http://g.co/ng/security#xss)
Error: unsafe value used in a resource URL context (see 

Answer 1

If you want to get the URL from a variable you need to enable binding by using [] or {{}} (never both at the same time, {{}} only works for strings, not for objects or arrays):

[src]="topic.video.url"

or

src="{{topic.video.url}}" 

If the URL gets removed by the DOM sanitizer, you can use a pipe like shown in In RC.1 some styles can't be added using binding syntax

import { Pipe, DomSanitizer } from '@angular/core';

@Pipe({name: 'safeResourceUrl'})
export class SafeResourceUrl {
  constructor(private sanitizer:DomSanitizer){}

  transform(url) {
    return this.sanitizer.bypassSecurityTrustResourceUrl(url);
  }
}

[src]="topic.video.url | safeResourceUrl"

You can also just apply

this.myUrl = this.sanitizer.bypassSecurityTrustResourceUrl(this.topic.video.url);

and bind to this instead

[src]="myUrl"

but the pipe is more reusable.