(easy) Ror : Create helper in view. But how?

I'm discovering R开发者_开发百科ails and I'm sure the way to do what I want is not what I did heure under. can you advice me on the manner to do this properly ??

I would like to create a helper and to use my "flag" variable to see which background I can use.

this is the behaviour I would like : - if I'm in /groups/:id , I want to display the background :id.jpg if it exists - if not, I would like to display a random image which is given by my javascript ImagesAleatoire();

Thanks for helping

<% flag = false
if (params[:id]) and (request.request_uri[1..7] == "groups/")
    file =  "/images/groups/"+params[:id]+".jpg";
else
    file = ""
end


if (File.exists?("public"+file)) %>
    <% flag = true %>
    <div id="header" style="background : url('<%= file %>') 114px top #2d8872;">
<% else %>
    <div id="header" style="background-color : #2d8872;">
<% end %>


<div id="searchzone">

    <div id="personnage">
    <% unless (flag)    %> <script>Images_Aleatoire(); </script> <% end %>
    </div> 
</div>
...

A helper like this under app/helpers/:

module FlagHelper
  def flag_exists?
    flag_file && File.exists?("public"+flag_file)
  end

  def flag_file
    "/images/groups/"+params[:id]+".jpg" if params[:id]
  end
end

And in your view:

<% if (flag_exists?) %>
    <div id="header" style="background : url('<%= flag_file %>') 114px top #2d8872;">
<% else %>
    <div id="header" style="background-color : #2d8872;">
<% end %>


<div id="searchzone">
  <div id="personnage">
    <% unless (flag_exists?) %>
      <script>Images_Aleatoire();</script>
    <% end %>
  </div> 
</div>

you could try this helper function

def group_bg_picture
  if (params[:controller] == "groups") && (params[:id])
    file = "/images/groups/#{params[:id]}.jpg";     
    "background:url('#{file}') 114px top #2d8872;" if File.exists? "public"+file 
  else
    ""
  end
end

and in your view:

<% bg_picture = group_bg_picture %>
<div id="header" style="<%= bg_picture || 'background-color : #2d8872;' %>">
<% unless (bg_picture.present?) %> 
  <script>Images_Aleatoire(); </script> 
<% end %>