Ajax on Rails
Stuart Halloway and Justin Gehtland
Copyright 2005-6 Relevance, LLC
Ajax on Rails Slide 1 of 54 www.codecite.com

License To Sample Code
This presentation is Copyright 2005-6, Relevance LLC. You may use any code you find here, subject to the terms below. If you want to deliver this
presentation, please send email to contact@relevancellc.com for permission and details.
Sample code associated with this presentation is Copyright (c) 2005-6 Relevance, LLC (www.relevancellc.com), unless otherwise marked. Code
citations from other projects are subject to the license(s) appropriate to those projects. You are responsible for complying with licenses for code you
use.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to
deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
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WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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Rails's Role in Ajax
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Agenda
Prototype Support
Ajax requests
auto-update
UI observers
Scriptaculous Helpers
effects
widgets
JavaScript Generation
JavaScriptGenerator
rjs
JSON
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What is Prototype?
Core Support for Dynamic Web Apps
Hides Browser Oddities
Used by Scriptaculous and Rico
Driven and Inspired by Ruby on Rails
Simple and Elegant
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Prototype's Role in Ajax
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Example: Ajax Search
Create a No-Op Form
Prototype Helper Observes User Action
Prototype Helper Submits Ajax Request
Server Renders a Partial
Update innerHTML of a Single Page Element
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Creating a No-Op Form
<%= start_form_tag('javascript:void%200',
{:method=> 'filter'}) %>
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Observing a Field By DOM ID
<%= observe_field :search,
:frequency => 0.5,
:update => 'ajaxWrapper',
:complete=>"Element.hide('spinner')",
:before=>"Element.show('spinner')",
:with=>"'search=' + encodeURIComponent(value)",
:url=>{:action=>'search', :only_path => false} %>
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Frequency to Check for Field Changes
<%= observe_field :search,
:frequency => 0.5,
:update => 'ajaxWrapper',
:complete=>"Element.hide('spinner')",
:before=>"Element.show('spinner')",
:with=>"'search=' + encodeURIComponent(value)",
:url=>{:action=>'search', :only_path => false} %>
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DOM ID to Update With Results
<%= observe_field :search,
:frequency => 0.5,
:update => 'ajaxWrapper',
:complete=>"Element.hide('spinner')",
:before=>"Element.show('spinner')",
:with=>"'search=' + encodeURIComponent(value)",
:url=>{:action=>'search', :only_path => false} %>
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Show/Hide Progress Indicator
<%= observe_field :search,
:frequency => 0.5,
:update => 'ajaxWrapper',
:complete=>"Element.hide('spinner')",
:before=>"Element.show('spinner')",
:with=>"'search=' + encodeURIComponent(value)",
:url=>{:action=>'search', :only_path => false} %>
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Query Parameters
<%= observe_field :search,
:frequency => 0.5,
:update => 'ajaxWrapper',
:complete=>"Element.hide('spinner')",
:before=>"Element.show('spinner')",
:with=>"'search=' + encodeURIComponent(value)",
:url=>{:action=>'search', :only_path => false} %>
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Server URL
<%= observe_field :search,
:frequency => 0.5,
:update => 'ajaxWrapper',
:complete=>"Element.hide('spinner')",
:before=>"Element.show('spinner')",
:with=>"'search=' + encodeURIComponent(value)",
:url=>{:action=>'search', :only_path => false} %>
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Why Full Path?
<%= observe_field :search,
:frequency => 0.5,
:update => 'ajaxWrapper',
:complete=>"Element.hide('spinner')",
:before=>"Element.show('spinner')",
:with=>"'search=' + encodeURIComponent(value)",
:url=>{:action=>'search', :only_path => false} %>
Pragforms Intended for Cross-Site Scripting
Most Ajax Apps Will Not Need This
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Rendered HTML + JavaScript
<input id="search" name="search" type="text" value="" />
<script type="text/javascript">
//<![CDATA[
new Form.Element.Observer('search', 0.5, function(element, value) {
Element.show('spinner');
new Ajax.Updater('ajaxWrapper',
'http://localhost:3010/user/search', {
onComplete:function(request){
Element.hide('spinner');
},
parameters:'search=' + encodeURIComponent(value)
})
})
//]]>
</script>
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Server Side Renders a Partial
def search
if params[:search] && params[:search].size>0
@user_pages, @users = paginate :users,
:per_page => 10,
:order => order_from_params,
:conditions=>User.conditions_by_like(params[:search])
logger.info @users.size
else
list
end
# params[:action] lets search and sort get _search and _sort
render :partial=>params[:action], :layout=>false
end
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Server Side Implementation Does Not Use Layout
def search
if params[:search] && params[:search].size>0
@user_pages, @users = paginate :users,
:per_page => 10,
:order => order_from_params,
:conditions=>User.conditions_by_like(params[:search])
logger.info @users.size
else
list
end
# params[:action] lets search and sort get _search and _sort
render :partial=>params[:action], :layout=>false
end
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Generalizing From The Search Example
Rails Providers Helper Methods Like observe_field
Helpers Generate JavaScript Code
Options Passed Through to Prototype/Scriptaculous
ruby hashes become JSON notation
Helpers Share Many Common Options
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XHR Helper Methods
Method Trigger
link_to_remote user clicks a link
form_remote_tag user submits a form
remote_form_for user submits a form
observe_field user changes a field
observe_form user changes any field in a form
submit_to_remote user clicks button
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Degradable Ajax
Ajax Apps That Also Function as Plain Old Web Pages
'Same URL' Strategy
pass Ajax-specific header
use partial for Ajax
wrap partial in template/layout for POW
'Different URL' Strategy
Ajax requests to one URL
Non-Ajax requests to a different URL
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Degrading on Same URL
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Degrading to Different URL
<%= link_to_remote('link',
{:update=>'jscheck'},
:href=>url_for(:action=>'no_javascript')) %>
<%= form_remote_tag(:update=>'jscheck',
:url=>{:action=>'yes_javascript'},
:html=>{:action=>'no_javascript', :method=>'post'}) %>
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What is Scriptaculous?
Effects and Widgets Library
Builds on Prototype
Driven and Inspired by Ruby on Rails
Simple and Elegant
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Scriptaculous's Role in Ajax
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Autocomplete
Popup List of Choices
Load Possible Matches While User Edits
Several Helper Methods
Simplest Version Assumes AR-Style Model Object
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Text Input
<%= text_field 'user', 'favorite_language' %></p>
<div class="auto_complete"
id="user_favorite_language_auto_complete"></div>
<%= auto_complete_field :user_favorite_language,
:url=>{:action=>'autocomplete_favorite_language'} %>
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DOM ID To AutoComplete
<%= text_field 'user', 'favorite_language' %></p>
<div class="auto_complete"
id="user_favorite_language_auto_complete"></div>
<%= auto_complete_field :user_favorite_language,
:url=>{:action=>'autocomplete_favorite_language'} %>
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Placeholder DIV For Suggestions
<%= text_field 'user', 'favorite_language' %></p>
<div class="auto_complete"
id="user_favorite_language_auto_complete"></div>
<%= auto_complete_field :user_favorite_language,
:url=>{:action=>'autocomplete_favorite_language'} %>
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Ajax Options (URL Required)
<%= text_field 'user', 'favorite_language' %></p>
<div class="auto_complete"
id="user_favorite_language_auto_complete"></div>
<%= auto_complete_field :user_favorite_language,
:url=>{:action=>'autocomplete_favorite_language'} %>
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Server Returns Simple HTML List
<ul class="autocomplete_list">
<% @languages.each do |l| %>
<li class="autocomplete_item"><%= l %></li>
<% end %>
</ul>
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Drag and Drop
Mark Elements as Draggable
Mark Elements as Drop Targets
Specify Callbacks
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Naming Convention: Model_Id
<ul id='pending_todo_list'>
<% @pending_todos.each do |item| %>
<% domid = "todo_#{item.id}" %>
<li class="pending_todo" id='<%= domid %>'><%= item.name %></li>
<%= draggable_element(domid, :ghosting=>true, :revert=>true) %>
<% end %>
</ul>
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Show Ghost Image While Dragging
<ul id='pending_todo_list'>
<% @pending_todos.each do |item| %>
<% domid = "todo_#{item.id}" %>
<li class="pending_todo" id='<%= domid %>'><%= item.name %></li>
<%= draggable_element(domid, :ghosting=>true, :revert=>true) %>
<% end %>
</ul>
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Snap Image Back After Drag
<ul id='pending_todo_list'>
<% @pending_todos.each do |item| %>
<% domid = "todo_#{item.id}" %>
<li class="pending_todo" id='<%= domid %>'><%= item.name %></li>
<%= draggable_element(domid, :ghosting=>true, :revert=>true) %>
<% end %>
</ul>
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DOM ID of Drop Target
<%= drop_receiving_element('pending_todos', :accept=>'completed_todo',
:complete=>"$('spinner').hide();",
:before=>"$('spinner').show();",
:hoverclass=>'hover',
:with=>"'todo=' + encodeURIComponent(element.id.split('_').last())",
:url=>{:action=>:todo_pending, :id=>@user})%>
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Only Accept Drops With Certain CSS Styles
<%= drop_receiving_element('pending_todos', :accept=>'completed_todo',
:complete=>"$('spinner').hide();",
:before=>"$('spinner').show();",
:hoverclass=>'hover',
:with=>"'todo=' + encodeURIComponent(element.id.split('_').last())",
:url=>{:action=>:todo_pending, :id=>@user})%>
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Various Ajax Options
<%= drop_receiving_element('pending_todos', :accept=>'completed_todo',
:complete=>"$('spinner').hide();",
:before=>"$('spinner').show();",
:hoverclass=>'hover',
:with=>"'todo=' + encodeURIComponent(element.id.split('_').last())",
:url=>{:action=>:todo_pending, :id=>@user})%>
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Set This CSS Class When a Valid Droppable Hovers
<%= drop_receiving_element('pending_todos', :accept=>'completed_todo',
:complete=>"$('spinner').hide();",
:before=>"$('spinner').show();",
:hoverclass=>'hover',
:with=>"'todo=' + encodeURIComponent(element.id.split('_').last())",
:url=>{:action=>:todo_pending, :id=>@user})%>
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Query Follows Naming Convention
<%= drop_receiving_element('pending_todos', :accept=>'completed_todo',
:complete=>"$('spinner').hide();",
:before=>"$('spinner').show();",
:hoverclass=>'hover',
:with=>"'todo=' + encodeURIComponent(element.id.split('_').last())",
:url=>{:action=>:todo_pending, :id=>@user})%>
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Distinct Style for Drop Areas
<style>
.hover {
background-color: #888888;
}
#pending_todos ul li, #completed_todos ul li {
list-style: none;
cursor: -moz-grab;
}
#pending_todos, #completed_todos {
border: 1px solid gray;
}
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Distinct Style for Valid Drops on Hover
<style>
.hover {
background-color: #888888;
}
#pending_todos ul li, #completed_todos ul li {
list-style: none;
cursor: -moz-grab;
}
#pending_todos, #completed_todos {
border: 1px solid gray;
}
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JavaScriptGenerator and RJS Templates
Added to Edge November 2005
Call Ruby Methods on Server-Side page Object
Generates JavaScript to Execute on Client
Methods for Prototype and Scriptaculous
Easy to Add Your Own
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Some Basic Generator Calls
RJS Expression (Server) Generated JavaScript on Client
page.alert('someMessage') alert("someMessage");
page.redirect_to(:action=>'foo') window.location.href = "http://www.example.com/foo";
page.call('myFunc', 'a_string', 42) myFunc("a_string", 42);
page.assign('myVar', 42) myVar = 42;
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Some Prototype Generator Calls
RJS Expression (Server) Generated JavaScript on Client
page.show('someDomId') Element.show("someDomId");
page.hide('someDomId') Element.hide("someDomId");
page.toggle('someDomId') Element.toggle("someDomId");
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Uses For JavaScriptGenerator
Update More Than One DOM Element
Update Element And Apply Behavior
Server Takes Control of The Page
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Rendering JavaScript From the Controller
render :update do |page|
page.replace_html 'pending_todos', :partial => 'pending_todos'
page.replace_html 'completed_todos', :partial => 'completed_todos'
page.sortable "pending_todo_list",
:url=>{:action=>:sort_pending_todos, :id=>@user}
end
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Drag Move Updates More Than One Element
render :update do |page|
page.replace_html 'pending_todos', :partial => 'pending_todos'
page.replace_html 'completed_todos', :partial => 'completed_todos'
page.sortable "pending_todo_list",
:url=>{:action=>:sort_pending_todos, :id=>@user}
end
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Drag Move Resets Sortable Behavior
render :update do |page|
page.replace_html 'pending_todos', :partial => 'pending_todos'
page.replace_html 'completed_todos', :partial => 'completed_todos'
page.sortable "pending_todo_list",
:url=>{:action=>:sort_pending_todos, :id=>@user}
end
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Invoking UI Effects
def update_many(options)
render :update do |page|
options.each do |k,v|
page.replace_html k, :partial=>v
page.visual_effect :highlight, k
end
end
end
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RJS Templates
View Files That End in .rjs
Same Object Model as render :update
Invoke Methods on page
Generated JavaScript Executes on Client
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JSON Support
Rails Adds to_json to Objects
implemented in ActiveSupport::JSON
Used For Model-Centric Ajax
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JSON Example: Periodically Updating Chat
class ChatJsonController < ApplicationController
def retrieve_chats
headers['Content-Type'] = "text/json"
@chats = get_chats
render :text=>@chats.to_json
end
end
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References
Resources
Codecite (Presentations and Code Samples), http://www.codecite.com
Relevance Consulting and Development, http://www.relevancellc.com/main/services
Relevance Training, http://www.relevancellc.com/main/training
Relevance Weblog, http://blogs.relevancellc.com
Projects Cited
Ajax Labs, http://www.codecite.com/projects/ajax_labs.zip
Rails Exploration Application, http://www.codecite.com/projects/rails_xt.zip
Pragmatic Chat Sample Application, http://www.codecite.com/projects/pragmatic_chat.zip
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