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README.md

ember-orbit Build Status Join the chat at https://gitter.im/orbitjs/orbit.js

ember-orbit (or "EO") is a library that integrates orbit.js with ember.js to provide flexibility and control in your application's data layer.

EO features:

  • Access to the full power of Orbit and its ecosystem, including compatible sources, buckets, and coordination strategies.

  • A data schema that's declared through simple model definitions.

  • Stores that wrap Orbit stores and provide access to their underlying data as easy to use records and record arrays. These stores can be forked, edited in isolation, and merged back to the original as a coalesced changeset.

  • Live-updating filtered record arrays and model relationships.

  • The full power of Orbit's composable query expressions.

  • The ability to connect any number of sources together with Orbit coordination strategies.

  • Orbit's git-like deterministic change tracking and history manipulation capabilities.

Relationship to Orbit

EO provides a thin "Emberified" layer over the top of some core primitives from Orbit, including Store, Cache, and Model classes. Most common developer interactions with Orbit will be through these classes.

However, EO does not attempt to wrap every base class from Orbit. For instance, you'll need to use Orbit's Coordinator and coordination strategies to define relationships between Orbit sources. In this way, you can install any Orbit Source or Bucket library and wire them together in your EO application.

Important: It's strongly recommended that you read the Orbit guides at orbitjs.com before using EO, since an understanding of Orbit is vital to making the most of EO.

Status

EO obeys semver and thus should not be considered to have a stable API until 1.0. Until then, any breaking changes in APIs or Orbit dependencies should be accompanied by a minor version bump of EO.

Demo

todomvc-ember-orbit is a simple TodoMVC example that uses EO to illustrate a number of possible configurations and application patterns.

Installation

As with any Ember addon, you can install EO in your project with:

ember install ember-orbit

EO depends on ember-auto-import to automatically import external dependencies, including @orbit/coordinator and @orbit/memory.

The generators for orbit sources and buckets will attempt to install any additional orbit-related dependencies.

Using EO

EO creates the following directories by default:

  • app/data-buckets - Factories for creating Orbit Buckets, which are used to save / load orbit application state.

  • app/data-models - For EO Model classes, which represent data records.

  • app/data-sources - Factories for creating Orbit Sources, which represent different sources of data.

  • app/data-strategies - Factories for creating Orbit coordination strategies.

Note that "factories" are simply objects with a create method that serves to instantiate an object. The factory interface conforms with the expectations of Ember's DI system.

EO installs the following services by default:

  • store - An ember-orbit Store to manage querying and updating models.

  • dataCoordinator - An @orbit/coordinator Coordinator that manages sources and coordination strategies between them.

  • dataSchema - An @orbit/data Schema that represents a schema for models that is shared by the store and other sources.

  • dataKeyMap - An @orbit/data KeyMap that manages a mapping between keys and local IDs for scenarios in which a server does not accept client-generated IDs.

By default, the store service is injected into every route and controller by default. The dataSchema and dataKeyMap will be injected into every Source.

All the directories and services configured by EO can be customized for your app, as described in the "Customizing EO" section below.

Defining models

Models are used to access the underlying data in an EO Store. They provide a proxy to get and set attributes and relationships. In addition, models are used to define the schema that's shared by the sources in your Orbit application.

The easiest way to create a Model is with the data-model generator:

ember g data-model planet

This will create the following module in app/data-models/planet.js:

import { Model } from 'ember-orbit';

export default class Planet extends Model {}

You can then extend your model to include keys, attributes, and relationships:

import { Model, attr, hasOne, hasMany, key } from 'ember-orbit';

export default class Planet extends Model {
  @attr('string') name;
  @hasMany('moon', { inverse: 'planet' }) moons;
  @hasOne('star') sun;
}

You can create polymorphic relationships by passing in an array of types:

import { Model, attr, hasOne, hasMany } from 'ember-orbit';

export default class PlanetarySystem extends Model {
  @attr('string') name;
  @hasMany(['moon', 'planet']) bodies;
  @hasOne(['star', 'binaryStar']) star;
}

Adding records

Records can be added in a couple ways. The easiest is to use the addRecord method on the store:

let planet = await store.addRecord({ type: 'planet', name: 'Earth' });
console.log(planet.name); // Earth

Alternatively, you can call store.update() and use the transform builder to build up a single Transform with any number of operations:

// planets added in a single `Transform`
let planets = await store.update(t => [
  t.addRecord({ type: 'planet', attributes: { name: 'Earth' } }),
  t.addRecord({ type: 'planet', attributes: { name: 'Venus' } })
]);

Note: calling update is a direct passthrough to the underlying Orbit store, so it's important to specify records in their full normalized form (see the Orbit guides).

Querying records

There are three unique methods used to query records:

  • store.query() - returns a promise that resolves to a static recordset.

  • store.liveQuery() - returns a promise that resolves to a live recordset that will be refreshed whenever the store's data changes.

  • store.cache.query() - returns a static set of in-memory results immediately.

All of these query methods take the same arguments as any other queryable Orbit source - see the Orbit guides for details.

For example, the following liveQuery should return a promise that resolves to a live resultset that will stay updated with the "terrestrial" planets in the store:

let planets = await store.liveQuery(qb =>
  qb
    .findRecords('planet')
    .filter({ attribute: 'classification', value: 'terrestrial' })
);

Unlike the Orbit Store, in which results are returned as static POJOs, results from EO queries are returned as records, i.e. instantiated versions of their associated Model class.

The attributes and relationships of records will be kept in sync with the backing store.

Note that the EO Store also supports the find method for compatibility with Ember's default expectations in routes. The following queries are async and call store.query internally:

// find all records of a type
store.find('planet');

// find a specific record by type and id
store.find('planet', 'abc123');

The following queries are synchronous and call store.cache.query internally:

// find all records of a type
store.cache.find('planet');

// find a specific record by type and id
store.cache.find('planet', 'abc123');

Updating records

Any records retrieved from a store or its cache will stay sync'd with the contents of that cache. Each attribute and relationship is a computed property that has getters and setters which pass through to the underlying store.

Let's say that you find a couple records directly in the store's cache and want to edit them:

let jupiter = store.cache.find('planet', 'jupiter');
let io = store.cache.find('moon', 'io');
let europa = store.cache.find('moon', 'europa');
let sun = store.cache.find('star', 'theSun');

jupiter.set('name', 'JUPITER!');
jupiter.get('moons').pushObject(io);
jupiter.get('moons').removeObject(europa);
jupiter.set('sun', sun);

Behind the scenes, these changes each result in a call to store.update. Of course, this method could also be called directly.

Forking and merging stores

Because EO stores and caches are just thin wrappers over their underlying Orbit equivalents, they share the same basic capabilities. Thus, EO stores can be forked and merged, just as described in the Orbit guides.

The same example can be followed:

  // start by adding two planets and a moon to the store
  await store.update(t => [
    t.addRecord(earth),
    t.addRecord(venus),
    t.addRecord(theMoon)
  ]);

  let planets = await store.query(q => q.findRecords('planet').sort('name')));
  console.log('original planets');
  console.log(planets);

  // fork the store
  forkedStore = store.fork();

  // add a planet and moons to the fork
  await forkedStore.update(t => [
    t.addRecord(jupiter),
    t.addRecord(io),
    t.addRecord(europa)
  ]);

  // query the planets in the forked store
  planets = await forkedStore.query(q => q.findRecords('planet').sort('name')));
  console.log('planets in fork');
  console.log(planets);

  // merge the forked store back into the original store
  await store.merge(forkedStore);

  // query the planets in the original store
  planets = await store.query(q => q.findRecords('planet').sort('name')));
  console.log('merged planets');
  console.log(planets);

And the same notes apply:

  • Once a store has been forked, the original and forked stores’ data can diverge independently.

  • A store fork can simply be abandoned without cost.

  • Merging a fork will gather the transforms applied since the fork point, coalesce the operations in those transforms into a single new transform, and then update the original store.

Important - One additional concern to be aware of is that EO will generate new records for each store. Care should be taken to not mix records between stores, since the underlying data in each store can diverge. If you need to access a record in a store's fork, just query the forked store or cache for that record.

Adding a "backup" source

The store's contents exist only in memory and will be cleared every time your app restarts. Let's try adding another source and use the dataCoordinator service to keep it in sync with the store.

We can use the data-source generator to create a backup source:

ember g data-source backup --from=@orbit/indexeddb

This will generate a source factory in app/data-sources/backup.js:

import SourceClass from '@orbit/indexeddb';

export default {
  create(injections = {}) {
    injections.name = 'backup';
    return new SourceClass(injections);
  }
};

Note that injections should include both a Schema and a KeyMap, which are injected by default for every EO application. We're also adding a name to uniquely identify the source within the coordinator. You could optionally specify a namespace to be used to name the IndexedDB database.

Every source that's defined in app/data-sources will be discovered automatically by EO and added to the dataCoordinator service.

Next let's define some strategies to synchronize data between sources.

Defining coordination strategies

There are four different types of coordination strategies that can be generated by default using the standard data-strategy generator:

  • request
  • sync
  • event-logging
  • log-truncation

Let's define a sync strategy to backup changes made to the store into our new backup source.

ember g data-strategy store-backup-sync --type=sync

This should create a SyncStrategy factory in app/data-strategies/store-backup-sync.js as follows:

import { SyncStrategy } from '@orbit/coordinator';

export default {
  create() {
    return new SyncStrategy({
      name: 'store-backup-sync',

      /**
       * The name of the source which will have its `transform` event observed.
       */
      source: 'store',

      /**
       * The name of the source which will be acted upon.
       *
       * When the source receives the `transform` event, the `sync` method
       * will be invoked on the target.
       */
      target: 'backup',

      /**
       * A handler for any errors thrown as a result of invoking `sync` on the
       * target.
       */
      // catch(e) {},

      /**
       * A filter function that returns `true` if `sync` should be performed.
       *
       * `filter` will be invoked in the context of this strategy (and thus will
       * have access to both `this.source` and `this.target`).
       */
      // filter(...args) {};

      /**
       * Should resolution of the target's `sync` block the completion of the
       * source's `transform`?
       *
       * Can be specified as a boolean or a function which which will be
       * invoked in the context of this strategy (and thus will have access to
       * both `this.source` and `this.target`).
       */
      blocking: true
    });
  }
};

You should also consider adding an event logging strategy to log events emitted from your sources to the browser console:

ember g data-strategy event-logging

Sources have another kind of log as well: a transform log, which tracks transforms that are applied. A log truncation strategy will keep the size of transform logs in check. It observes the sources associated with the strategy and truncates their transform logs when a common transform has been applied to them all. Let's add a log truncation strategy as well:

ember g data-strategy log-truncation

Activating the coordinator

Next we'll need to activate our coordinator as part of our app's boot process. The coordinator requires an explicit activation step because the process is async and we may want to allow developers to do work beforehand.

In our case, we want to restore our store from the backup source before we enable the coordinator. Let's do this in our application route's beforeModel hook (in app/routes/application.js):

import Route from '@ember/routing/route';
import { inject as service } from '@ember/service';

export default class ApplicationRoute extends Route {
  @service dataCoordinator;

  async beforeModel() {
    // Populate the store from backup prior to activating the coordinator
    const backup = this.dataCoordinator.getSource('backup');
    const transform = await backup.pull(q => q.findRecords());
    await this.store.sync(transform);

    await this.dataCoordinator.activate();
  }
}

This code first pulls all the records from backup and then syncs them with the main store before activating the coordinator. In this way, the coordination strategy that backs up the store won't be enabled until after the restore is complete.

Defining a data bucket

Data buckets are used by sources and key maps to load and persist state. To create a new bucket, run the generator:

ember g data-bucket main

By default this will create a new bucket factory based on @orbit/indexeddb-bucket. It will also create an initializer that injects this bucket into all your sources and key maps.

Customizing EO

The types, collections, and services used by EO can all be customized for your application via settings under the orbit key in config/environment:

module.exports = function(environment) {
  let ENV = {
    // ... other settings here

    // Default Orbit settings (any of which can be overridden)
    orbit: {
      types: {
        bucket: 'data-bucket',
        model: 'data-model',
        source: 'data-source',
        strategy: 'data-strategy'
      },
      collections: {
        buckets: 'data-buckets',
        models: 'data-models',
        sources: 'data-sources',
        strategies: 'data-strategies'
      },
      services: {
        store: 'store',
        coordinator: 'data-coordinator',
        schema: 'data-schema',
        keyMap: 'data-key-map'
      },
      skipStoreService: false,
      skipStoreInjections: false,
      skipCoordinatorService: false,
      skipSchemaService: false,
      skipKeyMapService: false
    }
  };

  return ENV;
};

Contributing to EO

Installation

  • git clone https://github.com/orbitjs/ember-orbit.git
  • cd ember-orbit
  • yarn install

Running Tests

  • yarn test

Acknowledgments

EO owes a great deal to Ember Data, which has influenced the design of many of EO's interfaces. Many thanks to the Ember Data Core Team, including Yehuda Katz, Tom Dale, and Igor Terzic, for their work.

It is hoped that, by tracking Ember Data's features and interfaces where possible, EO will also be able to contribute back to Ember Data.

License

Copyright 2014-2019 Cerebris Corporation. MIT License (see LICENSE for details).

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