#125 Dynamic Layouts

Discover how to dynamically change the layout using content in the database. Check out this episode for details.

script/generate migration add_layout_to_blogs layout_name:string custom_layout_content:text
rake db:migrate
gem install liquid

# controllers/application.rb
def load_blog
  @current_blog = Blog.find_by_subdomain(current_subdomain)
  if @current_blog.nil?
    flash[:error] = "Blog invalid"
    redirect_to root_url
  else
    self.class.layout(@current_blog.layout_name || 'application')
  end
end

# config/environment.rb
config.gem 'liquid'

<!-- layouts/custom.html.erb -->
<%= Liquid::Template.parse(@current_blog.custom_layout_content).
      render('page_content' => yield, 'page_title' => yield(:title)) %>

<!-- blogs/_form.html.erb -->
<p>
  <%= f.label :layout_name %><br />
  <%= f.select :layout_name, [["Standard", 'application'], ["Plain", 'plain'], ["Custom", 'custom']] %>
</p>
<p>
  <%= f.label :custom_layout_content %><br />
  <%= f.text_area :custom_layout_content, :rows => 12 %>
</p>

UPDATE: As Pratik mentioned in the comments, the above code is not thread safe. Here is a better way to handle the layout which is thread safe.

# application.rb
layout :set_layout

def load_blog
  @current_blog = Blog.find_by_subdomain(current_subdomain)
  if @current_blog.nil?
    flash[:error] = "Blog invalid"
    redirect_to root_url
  end
end

def set_layout
  (@current_blog && @current_blog.layout_name) || 'application'
end