upload.rb

#controller
class UploadMaterialController < ApplicationController
    def index
    end
    def upload
        @user = current_user
        @upload=UploadMaterial.new(params[:upload_material])
        @upload[:author]=current_user
        name=@upload[:name].original_filename
        directory="public/uploads/materials"
        if UploadMaterial.find_by_name(name) == nil
            path=File.join(directory,name)
            File.open(path,"wb"){ |f| f.write(params[:upload_material][:name].read) }
            @upload[:size]=(File.size("#{path}"))/1024.0
            if @upload.save
                flash[:notice]="File saved"
            else
                flash[:notice]="#{@upload[:size]},#{params[:upload_material]}"
            end
        else
            flash[:notice]="File name exists, please upload the file with other name"
        end

    end
end
#model
class UploadMaterial < ActiveRecord::Base
  belongs_to:author,:class_name=>'User'
#  validates_presence_of:subject,:name,:description,:size
end
#view

<div id="content-header">
  <img src="/images/admission/admission_page_logo.jpg" />
  <h1>Admission</h1>
  <h3>Step 1 - Student details</h3>
  <div id="app-back-button">
    <%= link_to_function image_tag("/images/buttons/back.png",:border => 0), "history.back()" %>
  </div>
</div>

<div id="page-yield">

  <% unless flash[:notice].nil? %>
    <p class="flash-msg"> <%= flash[:notice] %> </p>
  <% end %>

  <% form_for(@upload, :url => {:action=> 'upload'}, :html=> {:multipart=>true}) do |s| %>
    <%= error_messages_for 'upload_material', :header_message => nil %>

    <div id="admission1_form">

      <div id="necessary-field-notification"> Fields marked with <span class="necessary-field">*</span> must be filled.</div>

        

      <span class="span-sub-heading">Personal Details</span>
      <hr class="sub-heading"></hr>


      <hr class="label-underline"></hr>

      <div class="label-field-pair">
        <label for="student_grade">Description:<span class="necessary-field">*</span></label>
        <div class="text-input-bg"><%= s.text_field :description %></div>
      </div>

      <hr class="label-underline"></hr>



      <div id="admission1_form_vertical_block_left">

        <div class="label-field-pair">
		  <% if @user.admin? %>
          <label for="student_grade">Course & Batch</label>
          <div class="text-input-bg"><%= select :subject, :subject_id, Subject.all.collect {|b| [b.name, b.id]} %></div>
		  <% end %>
        </div>

        <hr class="label-underline"></hr>

      <div id="admission1_form_vertical_block_right">
        <script>
          (function($){$.fn.filestyle=function(options){var settings={width:250};if(options){$.extend(settings,options);};return this.each(function(){var self=this;var wrapper=$("<div>").css({"width":settings.imagewidth+"px","height":settings.imageheight+"px","background":"url("+settings.image+") 0 0 no-repeat","background-position":"right","display":"inline","position":"absolute","overflow":"hidden"});var filename=$('<input class="file">').addClass($(self).attr("class")).css({"display":"inline","width":settings.width+"px"});$(self).before(filename);$(self).wrap(wrapper);$(self).css({"position":"relative","height":settings.imageheight+"px","width":settings.width+"px","display":"inline","cursor":"pointer","opacity":"0.0"});if($.browser.mozilla){if(/Win/.test(navigator.platform)){$(self).css("margin-left","-142px");}else{$(self).css("margin-left","-168px");};}else{$(self).css("margin-left",settings.imagewidth-settings.width+"px");};$(self).bind("change",function(){filename.val($(self).val());});});};})(jQuery);
        </script>
        <span class="span-sub-heading">Upload Material</span>
        <hr class="sub-heading"></hr>
        <div class="label-field-pair">
          <label for="student_image_file">Upload  (	10MB max)</label>
          <div class="text-input-bg"><%= s.file_field :name %></div>

        </div>
      </div>
      <div class="extender">

      </div>

    <%= submit_tag "", :value => "► Save & Proceed", :class => "submit_button" %>
  <% end %>

</div>