WIP! (TODO: Tests)

About

• Auto-syncs records in client-side JS (through a Model DSL) from changes in the backend Rails server through ActionCable
• Auto-updates DOM elements mapped to a record attribute, from changes. (Optional Plugin)
• Automatically resyncs after client-side reconnection.

live_record is intentionally designed for read-only one-way syncing from the backend server, and does not support pushing changes to the Rails server from the client-side JS. Updates from client-side then is intended to use the normal HTTP REST requests.

Requirements

• >= Rails 5.0

Demo

• https://live-record-example.herokuapp.com/

Usage Example

• on the client-side:

  // instantiate a Book object
  var book = new LiveRecord.Model.all.Book({
    id: 1,
    title: 'Harry Potter',
    author: 'J. K. Rowling',
    created_at: '2017-08-02T12:39:49.238Z',
    updated_at: '2017-08-02T12:39:49.238Z'
  });
  // store this Book object into the JS store
  book.create();

  // the store is accessible through
  LiveRecord.Model.all.Book.all;

  // all records in the JS store are automatically subscribed to the backend LiveRecordChannel, which meant syncing (update / destroy) changes from the backend

  // you can add a callback that will be invoked whenever the Book object has been updated
  book.addCallback('after:update', function() {
    // let's say you update the DOM elements here when the attributes have changed
  });

• on the backend-side, you can handle attributes authorisation:

  # app/models/book.rb
  class Book < ApplicationRecord
    def self.live_record_whitelisted_attributes(book, current_user)
      # Add attributes to this array that you would like `current_user` to have access to when syncing this particular `book`
      # empty array means not-authorised
      if book.user == current_user
        [:title, :author, :created_at, :updated_at, :reference_id, :origin_address]
      elsif current_user.present?
        [:title, :author, :created_at, :updated_at]
      else
        []
      end
    end
  end

• whenever a Book (or any other Model record that you specified) has been updated / destroyed, there exists an after_update_commit and an after_destroy_commit ActiveRecord callback that will broadcast changes to all subscribed JS clients

Setup

• Add the following to your Gemfile:

  gem 'live_record', '~> 0.0.1'

• Run:

  bundle install

• Install by running:

  rails generate live_record:install

rails generate live_record:install --live_dom=false if you do not need the LiveDom plugin; --live_dom=true by default

• Run migration to create the live_record_updates table, which is going to be used for client reconnection resyncing:

  rake db:migrate

• Update your app/channels/application_cable/connection.rb, and add current_user method, unless you already have it:

  module ApplicationCable
    class Connection < ActionCable::Connection::Base
      identified_by :current_user

      def current_user
        # write something here if you have a current_user, or you may just leave this blank. Example below when using `devise` gem:
        # User.find_by(id: cookies.signed[:user_id])
      end
    end
  end

• Update your model files (only those you would want to be synced), and insert the following public method:

automatically updated if you use Rails scaffold or model generator

### Example 1 - Simple Usage

  # app/models/book.rb (example 1)
  class Book < ApplicationRecord
    def self.live_record_whitelisted_attributes(book, current_user)
      # Add attributes to this array that you would like current_user to have access to when syncing.
      # Defaults to empty array, thereby blocking everything by default, only unless explicitly stated here so.
      [:title, :author, :created_at, :updated_at]
    end
  end

### Example 2 - Advanced Usage

  # app/models/book.rb (example 1)
  class Book < ApplicationRecord
    def self.live_record_whitelisted_attributes(book, current_user)
      # Notice that from above, you also have access to `book` (the record currently requested by the client to be synced),
      # and the `current_user`, the current user who is trying to sync the `book` record.
      if book.user == current_user
        [:title, :author, :created_at, :updated_at, :reference_id, :origin_address]
      elsif current_user.present?
        [:title, :author, :created_at, :updated_at]
      else
        []
      end
    end
  end

• For each Model you want to sync, insert the following in your Javascript files.

automatically updated if you use Rails scaffold or controller generator

### Example 1 - Model

  // app/assets/javascripts/books.js
  LiveRecord.Model.create(
    {
      modelName: 'Book' // should match the Rails model name
      plugins: {
        LiveDOM: true // remove this if you do not need `LiveDom`
      }
    }
  )

### Example 2 - Model + Callbacks

  // app/assets/javascripts/books.js
  LiveRecord.Model.create(
    {
      modelName: 'Book',
      callbacks: {
        'on:connect': [
          function() {
            console.log(this); // `this` refers to the current `Book` record that has just connected for syncing
          }
        ],
        'after:update': [
          function() {
            console.log(this); // `this` refers to the current `Book` record that has just been updated with changes synced from the backend
          }
        ]
      }
    }
  )

#### Model Callbacks supported:
* `on:connect`
* `on:disconnect`
* `on:response_error`
* `before:create`
* `after:create`
* `before:update`
* `after:update`
* `before:destroy`
* `after:destroy`

> Each callback should map to an array of functions

* `on:response_error` supports a function argument: The "Error Code". i.e.

  ### Example 3 - Handling Response Error

  ```js
  LiveRecord.Model.create(
    {
      modelName: 'Book',
      callbacks: {
        'on:response_error': [
          function(errorCode) {
            console.log(errorCode); // errorCode is a string, representing the type of error. See Response Error Codes below:
          }
        ]
      }
    }
  )
  ```

  #### Response Error Codes:
  * `"forbidden"` - Current User is not authorized to sync record changes. Happens when Model's `live_record_whitelisted_attributes` method returns empty array.
  * `"bad_request"` - Happens when `LiveRecord.Model.create({modelName: 'INCORRECTMODELNAME'})`

• Load the records into the JS Model-store through JSON REST (i.e.):

### Example 1 - Using Default Loader (Requires JQuery)

Your controller must also support responding with JSON in addition to HTML. If you used scaffold or controller generator, this should already work immediately.

  <!-- app/views/books/index.html.erb -->
  <script>
    // `loadRecords` asynchronously loads all records (using the current URL) to the store, through a JSON AJAX request.
    // in this example, `loadRecords` will load JSON from the current URL which is /books
    LiveRecord.helpers.loadRecords({modelName: 'Book'})
  </script>

  <!-- app/views/posts/index.html.erb -->
  <script>
    // You may also pass in a callback for synchronous logic
    LiveRecord.helpers.loadRecords({
      modelName: 'Book',
      onLoad: function(records) {
        // ...
      },
      onError: function(jqxhr, textStatus, error) {
        // ...
      }
    })
  </script>

### Example 2 - Using Custom Loader

  // do something here that will fetch Book record attributes...
  // as an example, say you already have the following attributes:
  var book1Attributes = { id: 1, title: 'Noli Me Tangere', author: 'José Rizal' }
  var book2Attributes = { id: 2, title: 'ABNKKBSNPLAko?!', author: 'Bob Ong' }

  // then we instantiate a Book object
  var book1 = new LiveRecord.Model.all.Book(book1Attributes);
  // then we push this Book object to the Book store, which then automatically subscribes them to changes in the backend
  book1.create();

  var book2 = new LiveRecord.Model.all.Book(book2Attributes);
  book2.create();

  // you can also add Instance callbacks specific only to this Object (supported callbacks are the same as the Model callbacks)
  book2.addCallback('after:update', function() {
    // do something when book2 has been updated after syncing
  })

Plugins

LiveDom (Requires JQuery)

• enabled by default, unless explicitly removed.
• LiveDom allows DOM elements' text content to be automatically updated, whenever the mapped record-attribute has been updated.

text content is safely escaped using JQuery's .text() function

Example 1 (Mapping to a Record-Attribute: after:update)

<span data-live-record-update-from='Book-24-title'>Harry Potter</span>

• data-live-record-update-from format should be MODELNAME-RECORDID-RECORDATTRIBUTE
• whenever LiveRecord.all.Book.all[24] has been updated/synced from backend, "Harry Potter" text above changes accordingly.
• this does not apply to only <span> elements. You can use whatever elements you like.

Example 2 (Mapping to a Record: after:destroy)

<section data-live-record-destroy-from='Book-31'>This example element is a container for the Book-31 record which can also contain children elements</section>

• data-live-record-destroy-from format should be MODELNAME-RECORDID
• whenever LiveRecord.all.Book.all[31] has been destroyed/synced from backend, the <section> element above is removed, and thus all of its children elements.

• this does not apply to only <section> elements. You can use whatever elements you like.

• You may combine data-live-record-destroy-from and data-live-record-update-from within the same element.

JS API

LiveRecord.Model.create(CONFIG)

• CONFIG (Object)
  • modelName: (String, Required)
  • callbacks: (Object)
    • on:connect: (Array of functions)
    • on:disconnect: (Array of functions)
    • on:response_error: (Array of functions; function argument = ERROR_CODE (String))
    • before:create: (Array of functions)
    • after:create: (Array of functions)
    • before:update: (Array of functions)
    • after:update: (Array of functions)
    • before:destroy: (Array of functions)
    • after:destroy: (Array of functions)
  • plugins: (Object)
    • LiveDom: (Boolean)
• returns the newly create MODEL

new LiveRecord.Model.all.MODELNAME(ATTRIBUTES)

• ATTRIBUTES (Object)
• returns a MODELINSTANCE of the the Model having ATTRIBUTES attributes

MODELINSTANCE.modelName()

• returns the model name (i.e. 'Book')

MODELINSTANCE.attributes

• the attributes object

MODELINSTANCE.ATTRIBUTENAME()

• returns the attribute value of corresponding to ATTRIBUTENAME. (i.e. bookInstance.id(), bookInstance.created_at())

MODELINSTANCE.subscribe()

• subscribes to the LiveRecordChannel. This instance should already be subscribed by default after being stored, unless there is a on:response_error or manually unsubscribed() which then you should manually call this subscribe() function after correctly handling the response error, or whenever desired.
• returns the subscription object (the ActionCable subscription object itself)

MODELINSTANCE.isSubscribed()

• returns true or false accordingly if the instance is subscribed

MODELINSTANCE.subscription

• the subscription object (the ActionCable subscription object itself)

MODELINSTANCE.create()

• stores the instance to the store, and then subscribe() to the LiveRecordChannel for syncing
• returns the instance

MODELINSTANCE.update(ATTRIBUTES)

• ATTRIBUTES (Object)
• updates the attributes of the instance
• returns the instance

MODELINSTANCE.destroy()

• removes the instance from the store, and then unsubscribe()
• returns the instance

MODELINSTANCE.addCallback(CALLBACKKEY, CALLBACKFUNCTION)

• CALLBACKKEY (String) see supported callbacks above
• CALLBACKFUNCTION (function Object)
• returns the function Object if successfuly added, else returns false if callback already added

MODELINSTANCE.removeCallback(CALLBACKKEY, CALLBACKFUNCTION)

• CALLBACKKEY (String) see supported callbacks above
• CALLBACKFUNCTION (function Object) the function callback that will be removed
• returns the function Object if successfully removed, else returns false if callback is already removed