SocketHelpers

Usage /Installation

(these instructions can be seen implemented in the socket_helpers_example repo or seen on a live site

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create rails app rails new App; cd App;

create a model rails g scaffold Todo content:string; rake db:migrate;

add gems gem 'socket_helpers' and gem 'websocket-rails'

add javascript requires to application.js

• //= require websocket_rails/main
• //= require socket_helpers

add jquery initializer for whatever models you need websocket resources for (singular, snake case).

  $(function(){
   SocketHelpers.initialize(["todo"], "http://localhost:3000/websocket")
  })

• the default websocket url (from the websocket-rails gem) is "/websocket"

include the controller helpers to application_controller

  class ApplicationController < ActionController::Base
    include SocketHelpers::ControllerHelpers
  end

Remove the default scaffold routes (resources :todos). This gem supports only query parameters, not path parameters. This limitation only applies to websocket_response endpoints. Other endpoints can use path parameters.

• i.e. parameters are never declared in the routes.rb file, but they are declared in controllers. For example, routes like DELETE /todos/MY_TODO_ID are not supported, but DELETE /todos?id=MY_TODO_ID are.

Create a HTML-serving endpoint rails g controller HtmlPages root

Create websocket API endpoints and write routes

  # routes.rb
  get "/", to: "html_pages#root"
  post "todos", to: "todos#create"
  delete "todos", to: "todos#destroy"

  # app/controllers/todos_controller.rb
  # all the default scaffold stuff can be deleted
  class TodosController < ApplicationController
    def create
      todo = Todo.create(todo_params)
      websocket_response(todo, "create")
      return false
    end
    def destroy
      todo = Todo.find_by(id: params[:id])
      todo.destroy
      websocket_response(todo, "destroy")
      return false
    end
    def todo_params
      params.permit(:content)
    end
  end

• the first argument of websocket_response can be a single record or an array. It cannot be a query. The second can be either create, destroy, or update (these values hard-coded into the app. The receiver-hooks for these events are automatically created by the javascript client.

• make sure to add a 'return' or 'render' after websocket_response to avoid "template not found" errors.

use the DSL for HTML in html_pages/root.html.erb. See below for a list of HTML components available.

  <h3>Create todo</h3>
  
  <%# This form will submit via AJAX %>
  <%# all forms do this by default. use <form skip-sockets> to prevent it.%>
  <form action="todos" method="POST">
    <input type="text" name="content" placeholder="content">
    <input type="submit" value="submit">
  </form>
  
  <%# a class value of "model_name-index" is special %>
  <%# and sets up this section as a container for a list of records %>
  <div class="todo-index">
    <h3>Todos</h3>
    <p template> <%# special attr defines this as the template for added records %>
      <span template-attr="content"></span><%# two-way databinding for 'content %>
      <form action="/todos" method="POST"
        <input type="hidden" name="_method" value="DELETE"
        <input type="hidden" name="id" template-attr="id"
        <input type="submit" value="remove"></input>
      </form>
      <br>
    </p>
    </ul>
  </div>
  
  <%# define some todos which will initially appear on the page %>
  <%# This serialization is done automatically during 'websocket_response' %>
  <% @todos = Todo.limit(1).map do |todo| %>
  <%   todo.attributes.merge('record_class' => 'todo') %>
  <% end %>
  
  <%# initial data for the page %>
  <%# update and delete listeners are set up for these ids %>
  <div init="todo">
    <%= Oj.dump @todos.to_a %>
    <%# make sure not to dump a query %>
  </div>

• This provides working 'index, 'create', and 'destroy' websocket functionality in quite few lines of HTML, which is mainly the point of this gem. 'update' is automatic as well. When a record is added to the page, a record-id attribute is automatically set to <record_class>,<id> on the newly-added template. This is used to lookup records.

remove CSRF token check

comment out the protect_from_forgery with: :exception line in application_controller

start rails server rails s;, open localhost:3000

It is a working todo-app with websockets. Try opening two browser windows at once.

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List of HTML components

• elements with a class of <model_name>-index become lists, with elements auto-removed and added in response to websocket events. For example, <div class="todo-index"></div>. These sections correspond to a single ActiveRecord class (underscore, singular i.e. todo_list_item for TodoListItem)

• inside a <model_name>-index element, an element with a template attribute becomes the template for added records. For example, <div template></div>

• inside a [template] element, the template-attr attribute is used to establish two-way databinding on an element. Its value is the name of the attribute. This can be used to set the value of form inputs or to change text nodes. For example,

  <input type="text" name="content" template-attr="content">
  <!-- or alternatively -->
  <span template-attr="content">

• all form submits are intercepted by event listeners by default. To override this, add the "skip-sockets" attribute to the form element. They submit AJAX requests using the url in the form's action attribute and the method in the form's method attribute (i.e. action="/todos" method="POST"). This works for GET and POST only, but PUT and DELETE can be used by adding a hidden input method i.e. input type="hidden" name="_method" value="PUT". This is the default Rails behavior anyway.

• To submit an id with a form, bind a hidden attribute i.e. <input type="hidden" name="id" template-attr='id'>

• Outside of [template]s, binding tags are a bit more verbose. <span binding-tag='todos,1,content'></span> where the three comma-separated arguments are <model_class>, <id>, and <attribute>. template-attr tags are automatically converted to binding-tag once new records are added to the page.

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Other notes

**Changing a classes' published class name

• Say I created a LocationCategorization scaffold but realized that I would rather publish the data using a record_class value of category instead of location_categorization. I don't want to undo the scaffold, so I add a method to the LocationCategorization class:

    class LocationCategorization < ActiveRecord::Base
      def published_class
        "category"
      end
    end

This particular method name is used as an optional override for the default published class name (record.class.to_s.underscore)

Loading initial data on the page

Without doing this, the page will be empty every time it is refreshed. The page needs to start out with a list of records loaded.

Create an html element with an init attribute set to a model class, i.e. todo. This element will be auto-hidden. In the html-serving controller method, make an instance variable for whatever data is going to be included (expects an array, not a single object or query). On the html page, use ERB to set the content of the [init] element to a JSON stringified version of your instance variable. For example, <div init="todo"><%= Oj.dump([User.first]) %></div>

How to do links with params

i.e. how to do

<a href="/my_link?with=params">My Link </a>

The way to do this is by building a form and disguising it as a link. Basically come up with some CSS style so the form looks like a link. I don't really know how to do the CSS, but the form HTML code is below. This has the effect of creating a button on the page with the desired link follow-through when clicked. In this example, the 'link-style' class has to be externally implemented.

<form skip-sockets class="link-style" action="/notepad" method="GET">
  <input type="hidden" name="name" template-attr='name'>
  <input type="submit" template-attr='name'>
</form>

Additional Helpers

you can make one html element toggle another open / close very easily.

Just make them 'siblings (share the same parent element) and give the trigger a toggles attribute with a value set to the CSS selector of the target. The target will be initially closed.

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Use of OJ gem for JSON

• I use the OJ gem here and Oj.dump because of an unsolved recursion bug in to_json I encountered.