upload_progress_helper.rb

用ruby on rails写的一个博客程序,还不错..ruby on rails的确是个好框架

module UploadProgress
  # Provides a set of methods to be used in your views to help with the
  # rendering of Ajax enabled status updating during a multipart upload.
  #
  # The basic mechanism for upload progress is that the form will post to a
  # hidden <iframe> element, then poll a status action that will replace the
  # contents of a status container.  Client Javascript hooks are provided for
  # +begin+ and +finish+ of the update.
  #
  # If you wish to have a DTD that will validate this page, use XHTML
  # Transitional because this DTD supports the <iframe> element.
  #
  # == Typical usage
  #
  # In your upload view:
  #
  #   <%= form_tag_with_upload_progress({ :action => 'create' }) %>
  #     <%= file_field "document", "file" %>
  #     <%= submit_tag "Upload" %>
  #     <%= upload_status_tag %>
  #   <%= end_form_tag %>
  #
  # In your controller:
  #
  #   class DocumentController < ApplicationController   
  #     upload_status_for  :create
  #     
  #     def create
  #       # ... Your document creation action
  #     end
  #   end
  #   
  # == Javascript callback on begin and finished
  #
  # In your upload view:
  #
  #   <%= form_tag_with_upload_progress({ :action => 'create' }, {
  #       :begin => "alert('upload beginning'), 
  #       :finish => "alert('upload finished')}) %>
  #     <%= file_field "document", "file" %>
  #     <%= submit_tag "Upload" %>
  #     <%= upload_status_tag %>
  #   <%= end_form_tag %>
  #
  #
  # == CSS Styling of the status text and progress bar
  #
  # See +upload_status_text_tag+ and +upload_status_progress_bar_tag+ for references
  # of the IDs and CSS classes used.
  #
  # Default styling is included with the scaffolding CSS.
  module UploadProgressHelper
    unless const_defined? :FREQUENCY
      # Default number of seconds between client updates
      FREQUENCY = 2.0 

      # Factor to decrease the frequency when the +upload_status+ action returns the same results
      # To disable update decay, set this constant to +false+
      FREQUENCY_DECAY = 1.8
    end
    
    # Contains a hash of status messages used for localization of
    # +upload_progress_status+ and +upload_progress_text+.  Each string is
    # evaluated in the helper method context so you can include your own 
    # calculations and string iterpolations.
    #
    # The following keys are defined:
    #
    # <tt>:begin</tt>::      Displayed before the first byte is received on the server
    # <tt>:update</tt>::     Contains a human representation of the upload progress
    # <tt>:finish</tt>::     Displayed when the file upload is complete, before the action has completed.  If you are performing extra activity in your action such as processing of the upload, then inform the user of what you are doing by setting +upload_progress.message+
    #
    @@default_messages = {
      :begin => '"Upload starting..."',
      :update => '"#{human_size(upload_progress.received_bytes)} of #{human_size(upload_progress.total_bytes)} at #{human_size(upload_progress.bitrate)}/s; #{distance_of_time_in_words(0,upload_progress.remaining_seconds,true)} remaining"',
      :finish => 'upload_progress.message.blank? ? "Upload finished." : upload_progress.message',
    }


    # Creates a form tag and hidden <iframe> necessary for the upload progress
    # status messages to be displayed in a designated +div+ on your page.
    #
    # == Initializations
    #
    # When the upload starts, the content created by +upload_status_tag+ will be filled out with
    # "Upload starting...".  When the upload is finished, "Upload finished." will be used.  Every
    # update inbetween the begin and finish events will be determined by the server +upload_status+
    # action.  Doing this automatically means that the user can use the same form to upload multiple
    # files without refreshing page while still displaying a reasonable progress.
    #
    # == Upload IDs
    #
    # For the view and the controller to know about the same upload they must share
    # a common +upload_id+.  +form_tag_with_upload_progress+ prepares the next available 
    # +upload_id+ when called.  There are other methods which use the +upload_id+ so the 
    # order in which you include your content is important.  Any content that depends on the 
    # +upload_id+ will use the one defined +form_tag_with_upload_progress+
    # otherwise you will need to explicitly declare the +upload_id+ shared among
    # your progress elements.
    #
    # Status container after the form:
    #
    #   <%= form_tag_with_upload_progress %>
    #   <%= end_form_tag %>
    #
    #   <%= upload_status_tag %>
    #
    # Status container before form:
    #
    #   <% my_upload_id = next_upload_id %>
    #
    #   <%= upload_status_tag %>
    #
    #   <%= form_tag_with_upload_progress :upload_id => my_upload_id %>
    #   <%= end_form_tag %>
    #
    # It is recommended that the helpers manage the +upload_id+ parameter.
    #
    # == Options
    #
    # +form_tag_with_upload_progress+ uses similar options as +form_tag+
    # yet accepts another hash for the options used for the +upload_status+ action.
    #
    # <tt>url_for_options</tt>:: The same options used by +form_tag+ including:
    # <tt>:upload_id</tt>:: the upload id used to uniquely identify this upload
    #
    # <tt>options</tt>:: similar options to +form_tag+ including:
    # <tt>:begin</tt>::   Javascript code that executes before the first status update occurs.
    # <tt>:finish</tt>::  Javascript code that executes after the action that receives the post returns.
    # <tt>:frequency</tt>:: number of seconds between polls to the upload status action.
    #
    # <tt>status_url_for_options</tt>:: options passed to +url_for+ to build the url
    # for the upload status action.
    # <tt>:controller</tt>::  defines the controller to be used for a custom update status action
    # <tt>:action</tt>::      defines the action to be used for a custom update status action
    #
    # Parameters passed to the action defined by status_url_for_options
    #
    # <tt>:upload_id</tt>::   the upload_id automatically generated by +form_tag_with_upload_progress+ or the user defined id passed to this method.
    #   
    def form_tag_with_upload_progress(url_for_options = {}, options = {}, status_url_for_options = {}, *parameters_for_url_method)
      
      ## Setup the action URL and the server-side upload_status action for
      ## polling of status during the upload

      options = options.dup

      upload_id = url_for_options.delete(:upload_id) || next_upload_id
      upload_action_url = url_for(url_for_options)

      if status_url_for_options.is_a? Hash
        status_url_for_options = status_url_for_options.merge({
          :action => 'upload_status', 
          :upload_id => upload_id})
      end

      status_url = url_for(status_url_for_options)
      
      ## Prepare the form options.  Dynamically change the target and URL to enable the status
      ## updating only if javascript is enabled, otherwise perform the form submission in the same 
      ## frame.
      
      upload_target = options[:target] || upload_target_id
      upload_id_param = "#{upload_action_url.include?('?') ? '&' : '?'}upload_id=#{upload_id}"
      
      ## Externally :begin and :finish are the entry and exit points
      ## Internally, :finish is called :complete

      js_options = {
        :decay => options[:decay] || FREQUENCY_DECAY,
        :frequency => options[:frequency] || FREQUENCY,
      }

      updater_options = '{' + js_options.map {|k, v| "#{k}:#{v}"}.sort.join(',') + '}'

      ## Finish off the updating by forcing the progress bar to 100% and status text because the
      ## results of the post may load and finish in the IFRAME before the last status update
      ## is loaded. 

      options[:complete] = "$('#{status_tag_id}').innerHTML='#{escape_javascript upload_progress_text(:finish)}';"
      options[:complete] << "#{upload_progress_update_bar_js(100)};"
      options[:complete] << "#{upload_update_object} = null"
      options[:complete] = "#{options[:complete]}; #{options[:finish]}" if options[:finish]

      options[:script] = true

      ## Prepare the periodic updater, clearing any previous updater

      updater = "if (#{upload_update_object}) { #{upload_update_object}.stop(); }"
      updater << "#{upload_update_object} = new Ajax.PeriodicalUpdater('#{status_tag_id}',"
      updater << "'#{status_url}', Object.extend(#{options_for_ajax(options)},#{updater_options}))"

      updater = "#{options[:begin]}; #{updater}" if options[:begin]
      updater = "#{upload_progress_update_bar_js(0)}; #{updater}"
      updater = "$('#{status_tag_id}').innerHTML='#{escape_javascript upload_progress_text(:begin)}'; #{updater}"
      
      ## Touch up the form action and target to use the given target instead of the
      ## default one. Then start the updater

      options[:onsubmit] = "if (this.action.indexOf('upload_id') < 0){ this.action += '#{escape_javascript upload_id_param}'; }"
      options[:onsubmit] << "this.target = '#{escape_javascript upload_target}';"
      options[:onsubmit] << "#{updater}; return true" 
      options[:multipart] = true

      [:begin, :finish, :complete, :frequency, :decay, :script].each { |sym| options.delete(sym) }

      ## Create the tags
      ## If a target for the form is given then avoid creating the hidden IFRAME

      tag = form_tag(upload_action_url, options, *parameters_for_url_method)

      unless options[:target]
        tag << content_tag('iframe', '', {