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Class FirebaseCacheService

whatitdoes

Wraps some angularfire2 read methods for returning data from Firebase with the added function of storing the data locally for offline use.

consumers

ApiService

providerscope

AppComponent

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Features:

  • Returns real-time Firebase data via Observables
  • While online Firebase data is stored locally (as data changes the local store is updated)
  • While offline local data is served if available
  • On reconnect, Observables update app with new Firebase data
  • Even while online, local data is used first when available which results in a faster load ux
  • If loaded from local store while online, and Firebase sends changes (usually a few moments later), the changes will be sent to all subscribers and the local store will be updated right away.

Hierarchy

  • FirebaseCacheService

Index

Constructors

Properties

Methods

Constructors

constructor

Properties

Private af

af: AngularFire

Angular Fire service used to connect to Firebase

cache

cache: FirebaseCache
  • In-memory cache containing ReplaySubjects that return the latest value for any given Firebase reference.
  • That value can come from a Firebase subscription or from the device if there is no internet connection.

Private localforage

localforage: LocalForageService

Angular 2 wrapper of localforage that allows storing data offline using asynchronous storage (IndexedDB or WebSQL) with a simple, localStorage-like API

Methods

Private getList

  • getList(key: string): void

  • Retrives a list if locally stored on the device

    • Lists are stored as individual objects, to allow for better offline reuse.
    • Each locally stored list uses a map to stitch together the list from individual objects

    Parameters

    • key: string

    Returns void

list

  • list(key: string, query?: FirebaseListFactoryOpts, objKey?: string): Observable<[any]>

  • Returns an Observable array of Firebase snapshot data

    • This method can be used in place of angularfire2's list method and it will work offline
    • Sets up a list via setupList if cache is empty for this reference.
    • Each list item is stored as a separate object for offline use. This allows offline access to the entire list or a specific object in the list if the list is stored offline.
    • Does not include angularfire2 meta-fields such as $key or $exists

    Parameters

    • key: string

      the Firebase reference for this list

    • Optional query: FirebaseListFactoryOpts

      optional angularfire2 query param. Allows all valid queries

    • Optional objKey: string

      used as the object key when storing each list item as an object for offline use via setupList

    Returns Observable<[any]>

object

  • object(key: string, query?: FirebaseObjectFactoryOpts): Observable<object>

  • Returns an Observable object of Firebase snapshot data

    • This method can be used in place of angularfire2's object method and it will work offline
    • Sets up a list via setupList if cache is empty for this reference
    • Does not include angularfire2 meta-fields such as $key or $value

    Parameters

    • key: string

      the Firebase reference for this list

    • Optional query: FirebaseObjectFactoryOpts

      optional angularfire2 query param. Allows all valid queries available for objects

    Returns Observable<object>

Private setList

  • setList(key: string, array: Array<any>, objKeyPartial: string): void

  • Stores a list for offline use

    • Stores each list item as a separate object using the relavant Firebase reference string to allow offline use of the entire list or just a specific object
    • Stores a map of all the objects, used to stitch together the list for local use

    Parameters

    • key: string
    • array: Array<any>
    • objKeyPartial: string

    Returns void

Private setupList

  • setupList(key: string, query?: FirebaseListFactoryOpts, objKey?: string): void
    • Sets up a FirebaseCache item that provides Firebase data
    • Subscribes to the list's Firebase reference
    • Gets the most recent locally stored non-null value and sends to all app subscribers via getList
    • When Firebase sends a value this FirebaseCache item is set to loaded, the new value is sent to all app subscribers, and the value is stored locally via setList

    Parameters

    • key: string

      passed directly from list's key param

    • Default value query: FirebaseListFactoryOpts = {}

      passed directly from list's query param

    • Optional objKey: string

      passed directly from list's objKey param

    Returns void

Private setupObject

  • setupObject(key: string, query?: FirebaseObjectFactoryOpts): void
    • Sets up a FirebaseCache item that provides Firebase data
    • Subscribes to the object's Firebase reference
    • Gets the most recent locally stored non-null value and sends to all app subscribers
    • When Firebase sends a value this FirebaseCache item is set to loaded, the new value is sent to all app subscribers, and the value is stored locally

    Parameters

    • key: string

      passed directly from object's key param

    • Default value query: FirebaseObjectFactoryOpts = {}

      passed directly from object's query param

    Returns void

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