We'll be using Todos in the post for our examples. Each todo has a content string value for the todo description and a done boolean to indicate if the todo item is completed.

Setup

First you’ll want to import AngularFireDatabase and AngularFireList as well as inject the former in your constructor:

app.component.ts

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs/Observable';

import { AngularFireDatabase, AngularFireList }
  from 'angularfire2/database';

@Component({ ... })
export class AppComponent implements OnInit {
  todos$: AngularFireList<any[]>;

  constructor(private af: AngularFireDatabase) {}

  ngOnInit() {
    // ...
  }

  addTodo(value: string): void {
    // ...
  }
  deleteTodo(todo: any): void {
    // ...
  }

  toggleDone(todo: any): void {
    // ...
  }

  updateTodo(todo: any, newValue: string): void {
    // ...
  }
}

You’ll also want to make sure that AngularFireDatabase is provided in your app module:

// ...

import { AngularFireModule } from 'angularfire2';
import { environment } from '../environments/environment';
import { AngularFireDatabase } from 'angularfire2/database';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    // ...
    AngularFireModule.initializeApp(environment.firebase),
    AngularFireAuthModule
  ],
  providers: [AngularFireDatabase],
  bootstrap: [AppComponent]
})
export class AppModule { }

Reading Todos

imply declare a class property of type AngularFireList and get the /todos node from your Firebase database with AngularFireDatabase.list in the OnInit lifecycle hook:

todos$: AngularFireList<any[]>;

ngOnInit() {
  this.todos$ = this.af.list('/todos');
}

this.todos$ = this.af.list('/todos', ref => 
  ref.limitToFirst(3)
);

<ul>
  <li *ngFor="let todo of (todos$ | async)" [class.done]="todo.done">
    {{ todo.content }}
  </li>
</ul>

Creating Todos

Adding a new todo item is really easy, just call push on your AngularFireList instance:

addTodo(value: string): void {
  this.todos$.push({ content: value, done: false });
}

Updating and Deleting Todos

To update or delete a todo, things are a bit different because you’ll need a reference to the todo item that is to be updated or deleted. This can be done with AngularFireDatabase.object. Objects inside a Firebase have a unique key available as $key:

Updating Todos

Here’s how you would toggle the completed state of a todo:

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toggleDone(todo: any): void {
  this.af.object('/todos/' + todo.$key)
    .update({ content: todo.content, done: !todo.done });
}

Or update its content:

updateTodo2(todo: any, newValue: string): void {
  this.af.object('/todos/' + todo.$key)
    .update({ content: newValue, done: todo.done });    
}

As an alternative to the update method on a Firebase object, you could also use set. Using the set method will create a new item if one doesn't exist and replaces to whole object, so its destructive.

Deleting Todos

Deleting an item is just as easy as updating it:

deleteTodo(todo: any): void {
  this.af.object('/todos/' + todo.$key).remove();
}

Note that set, update and remove return a promise to you can chain then/catch calls to let you act on a successful operation or an error.