ChrisCodes.com

I've been playing with the Ajax Scaffolding gem for rails. Very cool stuff. It struck me funny when I read there was no magic way to say what columns appear, other than hard coding them in the view. Originally, I felt the same way when I first looked at generated views in general. But starting to hard code stuff in those beautifully useful views was getting me. I quickly remembered that Ruby is full of Magic, and figured out a way.

In this example, my database table name is sites. So in typical rails fashion, my model is site.rb, my controller is sites_controller.rb, and it's views are in app/views/sites/
The Ajax Scaffold generated view that displays the fields is named app/views/sites/_site.rhtml

The component action in the AjaxScaffold generated controller looks something like this:

  def component
    update_params :default_scaffold_id => "site", :default_sort => nil, :default_sort_direction => "asc"
     
    @sort_sql = Site.scaffold_columns_hash[current_sort(params)].sort_sql rescue nil
    @sort_by = @sort_sql.nil? ? "#{Site.table_name}.#{Site.primary_key} asc" : @sort_sql  + " " + current_sort_direction(params)
    @paginator, @sites = paginate(:sites, :order => @sort_by, :per_page => default_per_page)
    
    render :action => "component", :layout => false
  end

So to setup which columns should be allowed to show up is a matter of adding one line defining an array of column names.

  def component
    update_params :default_scaffold_id => "site", :default_sort => nil, :default_sort_direction => "asc"
     
    @sort_sql = Site.scaffold_columns_hash[current_sort(params)].sort_sql rescue nil
    @sort_by = @sort_sql.nil? ? "#{Site.table_name}.#{Site.primary_key} asc" : @sort_sql  + " " + current_sort_direction(params)
    @paginator, @sites = paginate(:sites, :order => @sort_by, :per_page => default_per_page)
    
    @allowed_columns = ["Name", "Url", "Code", "Lang"]    render :action => "component", :layout => false  end

Then in app/views/sites/_column_headings.rhtml we add a simple if statement to see if the column is supposed to display.

<%

 for scaffold_column in scaffold_columns

  if @allowed_columns.include? scaffold_column.label

    column_sort_direction = column_sort_direction(scaffold_column.name, params)

    sort_params = params.merge(:controller => '/sites', :action => 'component_update', :sort => scaffold_column.name, :sort_direction => column_sort_direction, :page => 1)

    column_header_id = scaffold_column_header_id(sort_params.merge(:column_name => scaffold_column.name))

%>

        <th id="<%= column_header_id %>" <%= "class=\\"sorted #{current_sort_direction(params)}\\"" if scaffold_column.name == current_sort(params) %>>

          <% if scaffold_column.sortable? %>

            <%= link_to_remote scaffold_column.label, 

                { :url => sort_params,

                :loading => "Element.addClassName('#{column_header_id}','loading');",

                :update => scaffold_content_id(sort_params) },

                { :href => url_for(sort_params) } %>

          <% else %>

            <p><%= scaffold_column.label %></p>

          <% end %>

        </th>

<%

  end

end

%>

      <th></th>

      

The same needs to be done in app/views/sites/_site.rhtml

<% # The following is used when the browser doesn't have javascript enabled %>
<% classAttr = cycle("", "class=\\"even\\"") %>
<% @options = params.merge(:controller => '/sites', :action => "view", :id => site.send("#{Site.primary_key}")) %>

<tr <%= classAttr %> id="<%= element_row_id(@options) %>" <%= "style=\\"display: none;\\"" if hidden %>>
<%
for scaffold_column in scaffold_columns
  if @allowed_columns.include? scaffold_column.label
%>
	  <% column_value = eval(scaffold_column.eval) rescue nil %>
	  <td class="<%= column_class(scaffold_column.name, column_value, current_sort(params)) %>" >
	    <%= format_column(column_value) %>
	  </td>
<%
  end
end
%>
  <td class="actions">
    <table cellpadding="0" cellspacing="0">
      <tr>
        <td class="indicator-container">
          <%= loading_indicator_tag(@options) %>
        </td>
        <td> 
          <% edit_options = @options.merge(:action => 'edit') %>
 	        <%= link_to_remote "Edit", 
   	                    { :url => edit_options, 
                          :loading => "Element.show('#{loading_indicator_id(@options)}');" },
   	                    { :href => url_for(edit_options) } %>
   	     </td>
   	     <td>
   	       <% delete_options = @options.merge(:action => 'destroy') %>
 	         <%= link_to_remote "Delete", 
   	                    { :url => delete_options, 
   	                      :confirm => 'Are you sure?',
                          :loading => "Element.show('#{loading_indicator_id(@options)}');" },
   	                    { :href => url_for( delete_options ) } %>
   	      </td>
   	    </tr>
   	  </table>
  </td>
</tr>  

That's it, now only the columns specified will appear. I'm sure there are other ways to acheive this, but this seems easy enough.