Provides a set of helpers for calling Prototype JavaScript functions, including functionality to call remote methods using Ajax. This means that you can call actions in your controllers without reloading the page, but still update certain parts of it using injections into the DOM. The common use case is having a form that adds a new element to a list without reloading the page.

To be able to use these helpers, you must include the Prototype JavaScript framework in your pages. See the documentation for ActionView::Helpers::JavaScriptHelper for more information on including the necessary JavaScript.

See link_to_remote for documentation of options common to all Ajax helpers.

See also ActionView::Helpers::ScriptaculousHelper for helpers which work with the Scriptaculous controls and visual effects library.

See JavaScriptGenerator for information on updating multiple elements on the page in an Ajax response.

Methods
Constants
CALLBACKS = Set.new([ :uninitialized, :loading, :loaded, :interactive, :complete, :failure, :success ] + (100..599).to_a)
AJAX_OPTIONS = Set.new([ :before, :after, :condition, :url, :asynchronous, :method, :insertion, :position, :form, :with, :update, :script ]).merge(CALLBACKS)
Public Instance methods
evaluate_remote_response()

Returns ‘eval(request.responseText)’ which is the JavaScript function that form_remote_tag can call in :complete to evaluate a multiple update return document using update_element_function calls.

     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 210
210:       def evaluate_remote_response
211:         "eval(request.responseText)"
212:       end
form_remote_for(object_name, *args, &proc)

Alias for remote_form_for

form_remote_tag(options = {}, &block)

Returns a form tag that will submit using XMLHttpRequest in the background instead of the regular reloading POST arrangement. Even though it‘s using JavaScript to serialize the form elements, the form submission will work just like a regular submission as viewed by the receiving side (all elements available in params). The options for specifying the target with :url and defining callbacks is the same as link_to_remote.

A "fall-through" target for browsers that doesn‘t do JavaScript can be specified with the :action/:method options on :html.

Example:

  form_remote_tag :html => { :action =>
    url_for(:controller => "some", :action => "place") }

The Hash passed to the :html key is equivalent to the options (2nd) argument in the FormTagHelper.form_tag method.

By default the fall-through action is the same as the one specified in the :url (and the default method is :post).

form_remote_tag also takes a block, like form_tag:

  <% form_remote_tag :url => '/posts' do -%>
    <div><%= submit_tag 'Save' %></div>
  <% end -%>
     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 172
172:       def form_remote_tag(options = {}, &block)
173:         options[:form] = true
174: 
175:         options[:html] ||= {}
176:         options[:html][:onsubmit] = 
177:           (options[:html][:onsubmit] ? options[:html][:onsubmit] + "; " : "") + 
178:           "#{remote_function(options)}; return false;"
179: 
180:         form_tag(options[:html].delete(:action) || url_for(options[:url]), options[:html], &block)
181:       end
link_to_remote(name, options = {}, html_options = {})

Returns a link to a remote action defined by options[:url] (using the url_for format) that‘s called in the background using XMLHttpRequest. The result of that request can then be inserted into a DOM object whose id can be specified with options[:update]. Usually, the result would be a partial prepared by the controller with render :partial.

Examples:

  link_to_remote "Delete this post", :update => "posts",
    :url => { :action => "destroy", :id => post.id }
  link_to_remote(image_tag("refresh"), :update => "emails",
    :url => { :action => "list_emails" })

You can also specify a hash for options[:update] to allow for easy redirection of output to an other DOM element if a server-side error occurs:

Example:

  link_to_remote "Delete this post",
    :url => { :action => "destroy", :id => post.id },
    :update => { :success => "posts", :failure => "error" }

Optionally, you can use the options[:position] parameter to influence how the target DOM element is updated. It must be one of :before, :top, :bottom, or :after.

The method used is by default POST. You can also specify GET or you can simulate PUT or DELETE over POST. All specified with options[:method]

Example:

  link_to_remote "Destroy", :url => person_url(:id => person), :method => :delete

By default, these remote requests are processed asynchronous during which various JavaScript callbacks can be triggered (for progress indicators and the likes). All callbacks get access to the request object, which holds the underlying XMLHttpRequest.

To access the server response, use request.responseText, to find out the HTTP status, use request.status.

Example:

  link_to_remote word,
    :url => { :action => "undo", :n => word_counter },
    :complete => "undoRequestCompleted(request)"

The callbacks that may be specified are (in order):

:loading:Called when the remote document is being loaded with data by the browser.
:loaded:Called when the browser has finished loading the remote document.
:interactive:Called when the user can interact with the remote document, even though it has not finished loading.
:success:Called when the XMLHttpRequest is completed, and the HTTP status code is in the 2XX range.
:failure:Called when the XMLHttpRequest is completed, and the HTTP status code is not in the 2XX range.
:complete:Called when the XMLHttpRequest is complete (fires after success/failure if they are present).

You can further refine :success and :failure by adding additional callbacks for specific status codes.

Example:

  link_to_remote word,
    :url => { :action => "action" },
    404 => "alert('Not found...? Wrong URL...?')",
    :failure => "alert('HTTP Error ' + request.status + '!')"

A status code callback overrides the success/failure handlers if present.

If you for some reason or another need synchronous processing (that‘ll block the browser while the request is happening), you can specify options[:type] = :synchronous.

You can customize further browser side call logic by passing in JavaScript code snippets via some optional parameters. In their order of use these are:

:confirm:Adds confirmation dialog.
:condition:Perform remote request conditionally by this expression. Use this to describe browser-side conditions when request should not be initiated.
:before:Called before request is initiated.
:after:Called immediately after request was initiated and before :loading.
:submit:Specifies the DOM element ID that‘s used as the parent of the form elements. By default this is the current form, but it could just as well be the ID of a table row or any other DOM element.
     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 132
132:       def link_to_remote(name, options = {}, html_options = {})  
133:         link_to_function(name, remote_function(options), html_options)
134:       end
observe_field(field_id, options = {})

Observes the field with the DOM ID specified by field_id and makes an Ajax call when its contents have changed.

Required options are either of:

:url:url_for-style options for the action to call when the field has changed.
:function:Instead of making a remote call to a URL, you can specify a function to be called instead.

Additional options are:

:frequency:The frequency (in seconds) at which changes to this field will be detected. Not setting this option at all or to a value equal to or less than zero will use event based observation instead of time based observation.
:update:Specifies the DOM ID of the element whose innerHTML should be updated with the XMLHttpRequest response text.
:with:A JavaScript expression specifying the parameters for the XMLHttpRequest. This defaults to ‘value’, which in the evaluated context refers to the new field value. If you specify a string without a "=", it‘ll be extended to mean the form key that the value should be assigned to. So :with => "term" gives "’term’=value". If a "=" is present, no extension will happen.
:on:Specifies which event handler to observe. By default, it‘s set to "changed" for text fields and areas and "click" for radio buttons and checkboxes. With this, you can specify it instead to be "blur" or "focus" or any other event.

Additionally, you may specify any of the options documented in link_to_remote.

     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 287
287:       def observe_field(field_id, options = {})
288:         if options[:frequency] && options[:frequency] > 0
289:           build_observer('Form.Element.Observer', field_id, options)
290:         else
291:           build_observer('Form.Element.EventObserver', field_id, options)
292:         end
293:       end
observe_form(form_id, options = {})

Like observe_field, but operates on an entire form identified by the DOM ID form_id. options are the same as observe_field, except the default value of the :with option evaluates to the serialized (request string) value of the form.

     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 299
299:       def observe_form(form_id, options = {})
300:         if options[:frequency]
301:           build_observer('Form.Observer', form_id, options)
302:         else
303:           build_observer('Form.EventObserver', form_id, options)
304:         end
305:       end
periodically_call_remote(options = {})

Periodically calls the specified url (options[:url]) every options[:frequency] seconds (default is 10). Usually used to update a specified div (options[:update]) with the results of the remote call. The options for specifying the target with :url and defining callbacks is the same as link_to_remote.

     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 141
141:       def periodically_call_remote(options = {})
142:          frequency = options[:frequency] || 10 # every ten seconds by default
143:          code = "new PeriodicalExecuter(function() {#{remote_function(options)}}, #{frequency})"
144:          javascript_tag(code)
145:       end
remote_form_for(object_name, *args, &proc)

Works like form_remote_tag, but uses form_for semantics.

This method is also aliased as form_remote_for
     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 184
184:       def remote_form_for(object_name, *args, &proc)
185:         options = args.last.is_a?(Hash) ? args.pop : {}
186:         concat(form_remote_tag(options), proc.binding)
187:         fields_for(object_name, *(args << options), &proc)
188:         concat('</form>', proc.binding)
189:       end
remote_function(options)

Returns the JavaScript needed for a remote function. Takes the same arguments as link_to_remote.

Example:

  <select id="options" onchange="<%= remote_function(:update => "options",
      :url => { :action => :update_options }) %>">
    <option value="0">Hello</option>
    <option value="1">World</option>
  </select>
     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 223
223:       def remote_function(options)
224:         javascript_options = options_for_ajax(options)
225: 
226:         update = ''
227:         if options[:update] && options[:update].is_a?(Hash)
228:           update  = []
229:           update << "success:'#{options[:update][:success]}'" if options[:update][:success]
230:           update << "failure:'#{options[:update][:failure]}'" if options[:update][:failure]
231:           update  = '{' + update.join(',') + '}'
232:         elsif options[:update]
233:           update << "'#{options[:update]}'"
234:         end
235: 
236:         function = update.empty? ? 
237:           "new Ajax.Request(" :
238:           "new Ajax.Updater(#{update}, "
239: 
240:         url_options = options[:url]
241:         url_options = url_options.merge(:escape => false) if url_options.is_a?(Hash)
242:         function << "'#{url_for(url_options)}'"
243:         function << ", #{javascript_options})"
244: 
245:         function = "#{options[:before]}; #{function}" if options[:before]
246:         function = "#{function}; #{options[:after]}"  if options[:after]
247:         function = "if (#{options[:condition]}) { #{function}; }" if options[:condition]
248:         function = "if (confirm('#{escape_javascript(options[:confirm])}')) { #{function}; }" if options[:confirm]
249: 
250:         return function
251:       end
submit_to_remote(name, value, options = {})

Returns a button input tag that will submit form using XMLHttpRequest in the background instead of regular reloading POST arrangement. options argument is the same as in form_remote_tag.

     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 195
195:       def submit_to_remote(name, value, options = {})
196:         options[:with] ||= 'Form.serialize(this.form)'
197: 
198:         options[:html] ||= {}
199:         options[:html][:type] = 'button'
200:         options[:html][:onclick] = "#{remote_function(options)}; return false;"
201:         options[:html][:name] = name
202:         options[:html][:value] = value
203: 
204:         tag("input", options[:html], false)
205:       end
update_element_function(element_id, options = {}, &block)
    # File vendor/rails/actionpack/lib/action_view/helpers/deprecated_helper.rb, line 5
 5:       def update_element_function(element_id, options = {}, &block)
 6:         content = escape_javascript(options[:content] || '')
 7:         content = escape_javascript(capture(&block)) if block
 8:         
 9:         javascript_function = case (options[:action] || :update)
10:           when :update
11:             if options[:position]
12:               "new Insertion.#{options[:position].to_s.camelize}('#{element_id}','#{content}')"
13:             else
14:               "$('#{element_id}').innerHTML = '#{content}'"
15:             end
16:           
17:           when :empty
18:             "$('#{element_id}').innerHTML = ''"
19:           
20:           when :remove
21:             "Element.remove('#{element_id}')"
22:           
23:           else
24:             raise ArgumentError, "Invalid action, choose one of :update, :remove, :empty"
25:         end
26:         
27:         javascript_function << ";\n"
28:         options[:binding] ? concat(javascript_function, options[:binding]) : javascript_function
29:       end
update_page(&block)

Yields a JavaScriptGenerator and returns the generated JavaScript code. Use this to update multiple elements on a page in an Ajax response. See JavaScriptGenerator for more information.

     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 624
624:       def update_page(&block)
625:         JavaScriptGenerator.new(@template, &block).to_s
626:       end
update_page_tag(html_options = {}, &block)

Works like update_page but wraps the generated JavaScript in a <script> tag. Use this to include generated JavaScript in an ERb template. See JavaScriptGenerator for more information.

html_options may be a hash of <script> attributes to be passed to ActionView::Helpers::JavaScriptHelper#javascript_tag.

     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 634
634:       def update_page_tag(html_options = {}, &block)
635:         javascript_tag update_page(&block), html_options
636:       end
Protected Instance methods
build_callbacks(options)
     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 679
679:       def build_callbacks(options)
680:         callbacks = {}
681:         options.each do |callback, code|
682:           if CALLBACKS.include?(callback)
683:             name = 'on' + callback.to_s.capitalize
684:             callbacks[name] = "function(request){#{code}}"
685:           end
686:         end
687:         callbacks
688:       end
build_observer(klass, name, options = {})
     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 662
662:       def build_observer(klass, name, options = {})
663:         if options[:with] && !options[:with].include?("=")
664:           options[:with] = "'#{options[:with]}=' + value"
665:         else
666:           options[:with] ||= 'value' if options[:update]
667:         end
668: 
669:         callback = options[:function] || remote_function(options)
670:         javascript  = "new #{klass}('#{name}', "
671:         javascript << "#{options[:frequency]}, " if options[:frequency]
672:         javascript << "function(element, value) {"
673:         javascript << "#{callback}}"
674:         javascript << ", '#{options[:on]}'" if options[:on]
675:         javascript << ")"
676:         javascript_tag(javascript)
677:       end
method_option_to_s(method)
     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 658
658:       def method_option_to_s(method) 
659:         (method.is_a?(String) and !method.index("'").nil?) ? method : "'#{method}'"
660:       end
options_for_ajax(options)
     # File vendor/rails/actionpack/lib/action_view/helpers/prototype_helper.rb, line 639
639:       def options_for_ajax(options)
640:         js_options = build_callbacks(options)
641:       
642:         js_options['asynchronous'] = options[:type] != :synchronous
643:         js_options['method']       = method_option_to_s(options[:method]) if options[:method]
644:         js_options['insertion']    = "Insertion.#{options[:position].to_s.camelize}" if options[:position]
645:         js_options['evalScripts']  = options[:script].nil? || options[:script]
646: 
647:         if options[:form]
648:           js_options['parameters'] = 'Form.serialize(this)'
649:         elsif options[:submit]
650:           js_options['parameters'] = "Form.serialize('#{options[:submit]}')"
651:         elsif options[:with]
652:           js_options['parameters'] = options[:with]
653:         end
654:       
655:         options_for_javascript(js_options)
656:       end