Rails Views: How do you pass a variable to a partial layout?

Question

In one of my views I apply a layout to a block of code:

# In app/views/sessions/new.html.erb
<% render :layout => 'home/shadow_box' do %>
  #... code for sign in form here
<% end %>

The layout is a div that has png shadows on all four sides.

Since I use this layout all over my site, I want to pass a variable to the layout that specifies the width of the shadowed div. I tried using content for in the code block:

# In app/views/sessions/new.html.erb
<% render :layout => 'home/shadow_box' do %>
  <% content_for :box_width %>640<% end %>
  #... code for sign in form here
<% end %>

# In app/views/home/_shadow_box.html.erb
<div class="shadow-one" style="width:<%= yield :box_width %>;">
  <div class="corner-a"></div>
  <div class="corner-b"></div>
  <div class="shadow-two">
    <div class="shadow-three">
      <div class="shadow-four">
        <%= yield %>
      </div>
    </div>
  </div>
</div>

This didn't work and instead resulted in a double render of the entire code block.

What's the best way to tackle this problem?

Answer 1

Figured it out.

From the API: "You can also yield multiple times in one layout and use block arguments to differentiate the sections."

Solution:

# In app/views/sessions/new.html.erb
<% render :layout => 'home/shadow_box' do | section | %>
  <%- case section when :box_width -%>
    #width goes here. I.e., 640px
  <%- when :content -%>
    #code block goes here
  <% end -%>
<% end %>

#In app/views/home/_shadow_box.html.erb
<div class="shadow-one" style="width:<%= yield :box_width %>;">
  <div class="corner-a"></div>
  <div class="corner-b"></div>
  <div class="shadow-two">
    <div class="shadow-three">
      <div class="shadow-four">
        <%= yield :content %>
      </div>
    </div>
  </div>
</div>

Answer 2

First you need to know the difference between layouts and partials . Partials are generally from the view but can also be used from the controller if you are using ajax. Layouts are almost always used in the controller.

First create a file in a shared folder such as application/ and in this folder put a file call it whatever you want but it will contain the material that you want to include all over your site. Then when you pass a variable to a partial it's called in the partial as a local variable. Also with partials you don't need to say render :partial => you just put render 'application/some_file'

So from the view you want this:

<%= render 'application/your_file', :div_size => '600' %>

And then from the partial in the folder such as application/your_file.html.erb do this:

<div style="width:<%= div_width %>px;">
   content
</div>