is it possible to access value from a model databasetable in the application.html.erb?

im trying to make a app

with users this users can join multiple groups - every group has the same menu on the page their group page is accessable about group/1 or group/2

so i wanted to put the the menu in the applicat开发者_运维百科ion.html.erb, with lnks depending on the group.id - but i dont know how to acces this id in the application.html.erb

This is often done using content_for in the layout. Let's say you want your menu in a certain div in application.html.erb:

# application.html.erb
<div id="menu_div>
  <ul>
  ... etc ...
  </ul>
</div>

Replace the inner content with a yield statement:

<div id="menu_div>
  <%= yield :group_menu %>
</div>

Then in the view template add the content_for block:

# page
<% content_for :group_menu do %>
  <ul>
  ... etc ...
  </ul>
<% end %>

Each page template can then define its own menu code in a content_for block. This can be further generalized by using a helper method in the block and passing in instance variables.

EDIT

Assuming @group is assigned in the controller, you might do something like:

<% content_for :group_menu do %>
  <%= show_me_the_menu(@group) %>
<% end %>

and in the helper (obviously contrived example):

def show_me_the_menu(group)
  content_tag :ul do
    group.users.collect do |user|
      concat(content_tag(:li, user.some_method))
    end
  end
end

The correct approach would be to set this in ApplicationController via before_filter and just use it as an instance variable in views.

So in controller set something like @links = some logic where you calculate your links based on current user.

In view you do something like:

<ul>
  <%- for link in @links -%>
    <li><%= link.title =>
  <%- end -%.
</ul>

Of course, you set your @links in ApplicationController only if you want your links to be available to all your controllers/views, which I think you do.

Rails Cells could also be used here http://cells.rubyforge.org/

i solved my problem in a different way now. i created in the group model a "menu" and this i render partial in the application.html.erb