render_with_missing_template¶ ↑

Rails 3 only. Add following line to your Gemfile:

gem 'render_with_missing_template'

app/controllers/test_controller.rb

def index
  # Renders template layouts/default/index if tests/index is missing
  render :if_missing => {:template => "layouts/default/index"}
end

app/views/index.html.erb

<!-- Renders nothing if "navigation2" is missing --> 
<%= render :partial => "navigation2", :if_missing => false %>

<!-- Renders template "layouts/defaults/navigation" if "navigation2" is missing -->
<%= render :partial => "navigation2", :if_missing => {:template => "layouts/defaults/navigation"} %>

app/controllers/test_controller.rb

def index
  # Renders template layouts/default/index if tests/index is missing
  render :if_missing => {:template => "layouts/default/index"}
end

def index
  # Renders template layouts/default/index if tests/index is missing inside layout 'nowhere'. Render options are merged with default options.
  # Not shure that it is good strategy to merge. May be, option is required.
  render :layout => 'nowhere', :if_missing => {:template => "layouts/default/index"}
end

app/views/index.html.erb

<!-- Raises TemplateMissing because there is no :if_missing option here. --> 
<%= render :partial => "navigation2" %>