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https://github.com/blaugold/firebase-rxjs

Firebase with Observables, Type Checking of Schema, Zone.js aware and Angular ready.
https://github.com/blaugold/firebase-rxjs

angular firebase rxjs static-typing typescript zone

Last synced: 27 days ago
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Firebase with Observables, Type Checking of Schema, Zone.js aware and Angular ready.

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# FirebaseRxJS



Firebase with Observables, Type Checking of Schema, Zone.js aware and Angular ready.

 

- Asynchronous results are returned as observables.

- Strings in `.child("pathSegment")` can be validated through static type checking and a schema interface.

- If zone.js is in scope firebase sdk runs in separate zone.

- For use in angular apps `FirebaseRxJSModule` is provided.



[email protected] and [email protected] are required.



TypeScript Docs:



- [firebase-rxjs](https://blaugold.github.io/firebase-rxjs/firebase-rxjs/)

- [firebase-rxjs-angular](https://blaugold.github.io/firebase-rxjs/firebase-rxjs-angular/)



```bash

npm install --save firebase-rxjs

# For angular module

npm install --save firebase-rxjs-angular 

```



## Configuration



Create a new `FirebaseApp` by passing in the config from [Firebase Console](https://console.firebase.google.com/).



```typescript

import { FirebaseApp } from 'firebase-rxjs'



const app = new FirebaseApp({ options: {

    apiKey: "...",

    authDomain: "...",

    databaseURL: "...",

    storageBucket: "...",

    messagingSenderId: "..."

}});



// Get a reference to `FirebaseAuth`

const auth = app.auth()



auth.createUserWithEmailAndPassword("...", "...").subscribe(user => {

  ...

})

```



## Usage



To get static type checking when accessing the database define a database schema interface.

Its best to compose the schema out of smaller interfaces. This keeps your schema clear and

allows you to easily access subsections with `db.ref('path/to/something')`.



```typescript

// database-schema.ts

export interface UserProfile {

  firstName: string

  lastName: string

  twitter: string

  profileImg: string

}



export interface Comment {

  text: string

  createdAt: number

  author: string

  authorId: string

}



export interface Comments {

  [commentId: string]: Comment

}



export interface BlogPost {

  title: string

  summary: string

  body: string

  author: string

  authorId: string

  publishedAt: number

  updatedAt: number

  comments: Comments

}



export interface DBSchema {

  users: {

    [userId: string]: UserProfile

  }

  blogPosts: {

    [postId: string]: BlogPost

  }

}

```



Now when getting a reference of the database use the schema interface as the type parameter.



```typescript

import { FirebaseApp } from 'firebase-rxjs'

import { DBSchema } from './database-schema.ts'



const app: FirebaseApp

const db = app.database()



// Now the compiler will yell at you if you use the wrong path segments.

db.ref().child('userz')



// Or if you go deeper in the tree pass a sub schema as the type parameter.

const commentsRef = db.ref('blogPosts/1/comments')



// Using a schema will also give you better IntelliSense when accessing the retrieved data.

commentsRef.onValue().list().subscribe(comments  => {

  comments[0].key

  comments[0].val.body

})

```



The result of onValue, onChildAdded, etc is a `DataSnapshotObservable` which is typed 

according to the previous calls and the schema. It provides some helpful methods to make working

with `DataSnapshots` easier, but the snapshots can be accessed directly too. 



Most methods overall mirror the firebase sdk and behave the same.



## Angular



Include the `FirebaseRxJSModule` in your root module. It is possible to provide multiple apps for

injection but only one primary app. The primary `FirebaseApp` will make itself, `FirebaseAuth` and

`FirebaseDatabase` injectable directly. Secondary apps have to be configured with an 

`InjectionToken` which will inject the `FirebaseApp`. 



```typescript

import { NgModule, InjectionToken } from '@angular/core'

import { FirebaseRxJSModule, FirebaseApp } from 'firebase-rxjs-angular'



const secondaryApp = new InjectionToken()



@NgModule({

  ...

  imports: [

    FirebaseRxJSModule.primaryApp({options: ... }),

    FirebaseRxJSModule.secondaryApp(secondaryApp, {options: ... }),

  ],

  ...

})

export class AppModule {}

```



## Zone.js



If `Zone` is globally available all calls to the firebase sdk will run in an isolated zone, forked 

from the root zone. Alternatively a zone can be passed to the `FirebaseApp` constructor. All other 

methods take the zone of their call site and schedule tasks with it. 



Motivation for this feature is a problem which lets all protractor tests timeout unless synchronization is 

turned off. The cause lies in how protractor determines when changes stemming from the last input 

have propagated and the next instruction or expectation can be executed. It does this by observing

whether or not MicroTasks and MacroTasks are scheduled to run. Once the queues of theses tasks are 

empty it's safe to assume the dom wont change. EventTasks like listeners on `WebSocket.onmessage` 

could run and change the dom but that is unpredictable and can not be factored in to the decision

when to proceed with the test. Now what if micro and macro tasks schedule new tasks themselves? 

Protractor again will wait until all tasks have run. And this is what is problematic. When using 

the database the firebase sdk sends a heartbeat by setting up a timeout which first sends the 

heartbeat and then reschedules the next timeout. The result is a recursive chain of never ending 

MacroTasks keeping the task queue dirty. Independently of that the firebase sdk sets up a long 

running (around 30 seconds) timeout during initialization timing out any test by itself. 



## Real Time



Its worth noting that all write operations and one off reads are scheduled as MacroTasks, 

meaning protractor or angular's `async` test helper will wait until these tasks have run. This is not 

true for observables returned from `.{on}{Value,ChildAdded,ChildRemove,ChildChanged,ChildMoved}()`.

The semantics of MacroTasks are that they are

guaranteed to execute at least once after some well understood delay.


For a real time databases like Firebase the correct tasks to use is the EventTask. This type of task

is expected to run zero or multiple times with unpredictable timing. So when using the methods 

starting with `on`, tests relying on zone.js will not wait for them to complete, unless the framework

is configured to wait for all EventTasks to be canceled. For each observable

which emits real time database events the library schedules an EventTask on subscription and cancels 

it when the observable is unsubscribed. To make testing these kinds of observables simpler a test helper for

the jasmine testing framework is included:



```typescript

import { asyncEvents } from 'firebase-rxjs'



describe('Suite', () => {

  it('should wait for EventTasks to clear', asyncEvents(async () => {

    const db: FirebaseDatabase

    // This observable will unsubscribe itself after emitting 3 events.

    db.ref().child('foo').onValue().take(3).subscribe()

    

    // Multiple observables or other asynchronous tasks will block the test until their 

    // resolution too.

    const res = await fetch('https://www.google.com')

  }))

})

```



End-to-end tests should poll content on the page under test, which is dependent on real time changes,  

until a expected state is reached or timeout.