Module: ActionView::Helpers::PrototypeHelper

Defined in:
lib/action_view/helpers/prototype_helper.rb

Overview

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.

Defined Under Namespace

Classes: JavaScriptGenerator

Constant Summary collapse

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)

Instance Method Summary collapse

Instance Method Details

#evaluate_remote_response ⇒ Object

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.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 274

def evaluate_remote_response
  "eval(request.responseText)"
end

#form_remote_tag(options = {}) ⇒ Object

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).



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# File 'lib/action_view/helpers/prototype_helper.rb', line 162

def form_remote_tag(options = {})
  options[:form] = true

  options[:html] ||= {}
  options[:html][:onsubmit] = "#{remote_function(options)}; return false;"
  options[:html][:action] = options[:html][:action] || url_for(options[:url])
  options[:html][:method] = options[:html][:method] || "post"

  tag("form", options[:html], true)
end

#link_to_remote(name, options = {}, html_options = {}) ⇒ Object

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 either render_partial or render_partial_collection.

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.

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.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 127

def link_to_remote(name, options = {}, html_options = {})  
  link_to_function(name, remote_function(options), html_options)
end

#observe_field(field_id, options = {}) ⇒ Object

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.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 351

def observe_field(field_id, options = {})
  if options[:frequency] && options[:frequency] > 0
    build_observer('Form.Element.Observer', field_id, options)
  else
    build_observer('Form.Element.EventObserver', field_id, options)
  end
end

#observe_form(form_id, options = {}) ⇒ Object

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.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 363

def observe_form(form_id, options = {})
  if options[:frequency]
    build_observer('Form.Observer', form_id, options)
  else
    build_observer('Form.EventObserver', form_id, options)
  end
end

#periodically_call_remote(options = {}) ⇒ Object

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.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 136

def periodically_call_remote(options = {})
   frequency = options[:frequency] || 10 # every ten seconds by default
   code = "new PeriodicalExecuter(function() {#{remote_function(options)}}, #{frequency})"
   javascript_tag(code)
end

#remote_form_for(object_name, object, options = {}, &proc) ⇒ Object Also known as: form_remote_for

Works like form_remote_tag, but uses form_for semantics.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 174

def remote_form_for(object_name, object, options = {}, &proc)
  concat(form_remote_tag(options), proc.binding)
  fields_for(object_name, object, options, &proc)
  concat('</form>', proc.binding)
end

#remote_function(options) ⇒ Object

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>



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# File 'lib/action_view/helpers/prototype_helper.rb', line 287

def remote_function(options)
  javascript_options = options_for_ajax(options)

  update = ''
  if options[:update] and options[:update].is_a?Hash
    update  = []
    update << "success:'#{options[:update][:success]}'" if options[:update][:success]
    update << "failure:'#{options[:update][:failure]}'" if options[:update][:failure]
    update  = '{' + update.join(',') + '}'
  elsif options[:update]
    update << "'#{options[:update]}'"
  end

  function = update.empty? ? 
    "new Ajax.Request(" :
    "new Ajax.Updater(#{update}, "

  url_options = options[:url]
  url_options = url_options.merge(:escape => false) if url_options.is_a? Hash
  function << "'#{url_for(url_options)}'"
  function << ", #{javascript_options})"

  function = "#{options[:before]}; #{function}" if options[:before]
  function = "#{function}; #{options[:after]}"  if options[:after]
  function = "if (#{options[:condition]}) { #{function}; }" if options[:condition]
  function = "if (confirm('#{escape_javascript(options[:confirm])}')) { #{function}; }" if options[:confirm]

  return function
end

#submit_to_remote(name, value, options = {}) ⇒ Object

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.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 184

def submit_to_remote(name, value, options = {})
  options[:with] ||= 'Form.serialize(this.form)'

  options[:html] ||= {}
  options[:html][:type] = 'button'
  options[:html][:onclick] = "#{remote_function(options)}; return false;"
  options[:html][:name] = name
  options[:html][:value] = value

  tag("input", options[:html], false)
end

#update_element_function(element_id, options = {}, &block) ⇒ Object

Returns a JavaScript function (or expression) that’ll update a DOM element according to the options passed.

  • :content: The content to use for updating. Can be left out if using block, see example.

  • :action: Valid options are :update (assumed by default), :empty, :remove

  • :position If the :action is :update, you can optionally specify one of the following positions: :before, :top, :bottom, :after.

Examples:

<%= javascript_tag(update_element_function("products", 
  :position => :bottom, :content => "<p>New product!</p>")) %>

<% replacement_function = update_element_function("products") do %>
  <p>Product 1</p>
  <p>Product 2</p>
<% end %>
<%= javascript_tag(replacement_function) %>

This method can also be used in combination with remote method call where the result is evaluated afterwards to cause multiple updates on a page. Example:

# Calling view
<%= form_remote_tag :url => { :action => "buy" }, 
  :complete => evaluate_remote_response %>
all the inputs here...

# Controller action
def buy
  @product = Product.find(1)
end

# Returning view
<%= update_element_function(
      "cart", :action => :update, :position => :bottom, 
      :content => "<p>New Product: #{@product.name}</p>")) %>
<% update_element_function("status", :binding => binding) do %>
  You've bought a new product!
<% end %>

Notice how the second call doesn’t need to be in an ERb output block since it uses a block and passes in the binding to render directly. This trick will however only work in ERb (not Builder or other template forms).

See also JavaScriptGenerator and update_page.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 245

def update_element_function(element_id, options = {}, &block)
  content = escape_javascript(options[:content] || '')
  content = escape_javascript(capture(&block)) if block
  
  javascript_function = case (options[:action] || :update)
    when :update
      if options[:position]
        "new Insertion.#{options[:position].to_s.camelize}('#{element_id}','#{content}')"
      else
        "$('#{element_id}').innerHTML = '#{content}'"
      end
    
    when :empty
      "$('#{element_id}').innerHTML = ''"
    
    when :remove
      "Element.remove('#{element_id}')"
    
    else
      raise ArgumentError, "Invalid action, choose one of :update, :remove, :empty"
  end
  
  javascript_function << ";\n"
  options[:binding] ? concat(javascript_function, options[:binding]) : javascript_function
end

#update_page(&block) ⇒ Object

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.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 668

def update_page(&block)
  JavaScriptGenerator.new(@template, &block).to_s
end

#update_page_tag(&block) ⇒ Object

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.



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# File 'lib/action_view/helpers/prototype_helper.rb', line 675

def update_page_tag(&block)
  javascript_tag update_page(&block)
end