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rails--rails/actioncable/app/javascript/action_cable/subscription.js
Richard Macklin c96139af71 Convert ActionCable javascript to ES2015 modules with modern build environment
We've replaced the sprockets `//= require` directives with ES2015
imports. As a result, the ActionCable javascript can now be compiled
with rollup (like ActiveStorage already is).

- Rename action_cable/index.js.erb -> action_cable/index.js

- Add rake task to generate a javascript module of the ActionCable::INTERNAL ruby hash

  This will allow us to get rid of ERB from the actioncable javascript,
  since it is only used to interpolate ActionCable::INTERNAL.to_json.

- Import INTERNAL directly in ActionCable Connection module

  This is necessary to remove a load-order dependency conflict in the
  rollup-compiled build. Using ActionCable.INTERNAL would result in a
  runtime error:
  ```
  TypeError: Cannot read property 'INTERNAL' of undefined
  ```
  because ActionCable.INTERNAL is not set before the Connection module
  is executed.

  All other ActionCable.* references are executed inside of the body of a
  function, so there is no load-order dependency there.

- Add eslint and eslint-plugin-import devDependencies to actioncable

  These will be used to add a linting setup to actioncable like the one
  in activestorage.

- Add .eslintrc to actioncable

  This lint configuration was copied from activestorage

- Add lint script to actioncable

  This is the same as the lint script in activestorage

- Add babel-core, babel-plugin-external-helpers, and babel-preset-env devDependencies to actioncable

  These will be used to add ES2015 transpilation support to actioncable
  like we have in activestorage.

- Add .babelrc to actioncable

  This configuration was copied from activestorage

- Enable loose mode in ActionCable's babel config

  This generates a smaller bundle when compiled

- Add rollup devDependencies to actioncable

  These will be used to add a modern build pipeline to actioncable like
  the one in activestorage.

- Add rollup config to actioncable

  This is essentially the same as the rollup config from activestorage

- Add prebuild and build scripts to actioncable package

  These scripts were copied from activestorage

- Invoke code generation task as part of actioncable's prebuild script

  This will guarantee that the action_cable/internal.js module is
  available at build time (which is important, because two other modules
  now depend on it).

- Update actioncable package to reference the rollup-compiled files

  Now that we have a fully functional rollup pipeline in actioncable, we
  can use the compiled output in our npm package.

- Remove build section from ActionCable blade config

  Now that rollup is responsible for building ActionCable, we can remove
  that responsibility from Blade.

- Remove assets:compile and assets:verify tasks from ActionCable

  Now that we've added a compiled ActionCable bundle to version control,
  we don't need to compile and verify it at publish-time.

  (We're following the pattern set in ActiveStorage.)

- Include compiled ActionCable javascript bundle in published gem

  This is necessary to maintain support for depending on the ActionCable
  javascript through the Sprockets asset pipeline.

- Add compiled ActionCable bundle to version control

  This mirrors what we do in ActiveStorage, and allows ActionCable to
  continue to be consumed via the sprockets-based asset pipeline when
  using a git source instead of a published version of the gem.
2018-11-02 08:41:05 -07:00

89 lines
2.8 KiB
JavaScript

// A new subscription is created through the ActionCable.Subscriptions instance available on the consumer.
// It provides a number of callbacks and a method for calling remote procedure calls on the corresponding
// Channel instance on the server side.
//
// An example demonstrates the basic functionality:
//
// App.appearance = App.cable.subscriptions.create("AppearanceChannel", {
// connected() {
// // Called once the subscription has been successfully completed
// },
//
// disconnected({ willAttemptReconnect: boolean }) {
// // Called when the client has disconnected with the server.
// // The object will have an `willAttemptReconnect` property which
// // says whether the client has the intention of attempting
// // to reconnect.
// },
//
// appear() {
// this.perform('appear', {appearing_on: this.appearingOn()})
// },
//
// away() {
// this.perform('away')
// },
//
// appearingOn() {
// $('main').data('appearing-on')
// }
// })
//
// The methods #appear and #away forward their intent to the remote AppearanceChannel instance on the server
// by calling the `perform` method with the first parameter being the action (which maps to AppearanceChannel#appear/away).
// The second parameter is a hash that'll get JSON encoded and made available on the server in the data parameter.
//
// This is how the server component would look:
//
// class AppearanceChannel < ApplicationActionCable::Channel
// def subscribed
// current_user.appear
// end
//
// def unsubscribed
// current_user.disappear
// end
//
// def appear(data)
// current_user.appear on: data['appearing_on']
// end
//
// def away
// current_user.away
// end
// end
//
// The "AppearanceChannel" name is automatically mapped between the client-side subscription creation and the server-side Ruby class name.
// The AppearanceChannel#appear/away public methods are exposed automatically to client-side invocation through the perform method.
const extend = function(object, properties) {
if (properties != null) {
for (let key in properties) {
const value = properties[key]
object[key] = value
}
}
return object
}
export default class Subscription {
constructor(consumer, params = {}, mixin) {
this.consumer = consumer
this.identifier = JSON.stringify(params)
extend(this, mixin)
}
// Perform a channel action with the optional data passed as an attribute
perform(action, data = {}) {
data.action = action
return this.send(data)
}
send(data) {
return this.consumer.send({command: "message", identifier: this.identifier, data: JSON.stringify(data)})
}
unsubscribe() {
return this.consumer.subscriptions.remove(this)
}
}