Angular 2 Pipe not found

Question

I followed this link to create my own time ago pipe: Angular 2 "time ago" pipe

but when I injected and used it, I saw the error:

Template parse errors: The pipe 'timeAgo' could not be found

Below is my code, please help me to resolve this issue, many thanks!!

timeAgo.pipe.ts

import { Pipe, ChangeDetectorRef } from '@angular/core';
import { AsyncPipe } from '@angular/common';
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/interval';
import 'rxjs/add/operator/startWith';

@Pipe({
    name: 'timeAgo',
    pure: false
})
export class TimeAgoPipe extends AsyncPipe {
    value: Date;
    timer: Observable<string>;

    constructor(private ref: ChangeDetectorRef){
        super(ref);
    }

    transform(obj: any, args?: any[]): any {
        if(obj instanceof Date) {
            this.value = obj;

            if(!this.timer) {
                this.timer = this.getObservable();
            }
            return this.timer;
        }
        return this.transform(obj, args);

    }

    private getObservable(){
      const INTERVAL = 1000 * 45;

      const ONE_MINUTE = 60;
      const ONE_HOUR = 60 * 60;
      const ONE_DAY = 60 * 60 * 24;
      const ONE_MONTH = 60 * 60 * 24 * 30;
      const ONE_YEAR = 60 * 60 * 24 * 30 * 12;

      return Observable.interval(INTERVAL).startWith(0).map(() => {
        // current time
        let now = Date.now();

        // time since message was sent in seconds
        let delta = (now - this.value.getTime()) / 1000;

        // format string
        if(delta < ONE_MINUTE) {
          return 'just now';        
        }
        if(delta < ONE_HOUR) {
          return Math.floor(delta / ONE_MINUTE) + 'min(s) ago';
        }
        if(delta < ONE_DAY) {
          return Math.floor(delta / ONE_HOUR) + 'hour(s) ago';
        }
        if(delta < ONE_MONTH) {
          return Math.floor(delta / ONE_DAY) + 'day(s) ago';
        }
        if(delta < ONE_YEAR) {
          return Math.floor(delta / ONE_MONTH) + 'month ago';
        }

      });
    }
}

main.ts

import { bootstrap }    from '@angular/platform-browser-dynamic';
import { enableProdMode, provide, PLATFORM_PIPES } from '@angular/core';
bootstrap(AppComponent, [
  APP_ROUTER_PROVIDERS,
  provide(PLATFORM_PIPES, {
    useValue: [TimeAgoPipe],
    multi: true
  })
]);

post.component.html

<ul *ngIf="posts">
  <li *ngFor="let post of posts">
    {{ post.created_at | timeAgo}}     
  </li>
</ul>

Answer 1

This occurs because your TimeAgoPipe inherits from AsyncPipe. I don't know about the behavior during the Angular2 beta builds, but Angular 2.2.x consistently fails to find inherited @Component, @Pipe and @Directive classes during template compilation for me.

It seems there are some very good reasons Angular2 doesn't support component inheritance: https://github.com/angular/angular/issues/7968

If you're looking for a TimeAgoPipe compatible with Angular 2.2, have a look at my answer here or have a direct look at the gist.