Assigning a body class to your page layout in Ruby on Rails

Posted on 30 April 2008

In your controller create a private method thus:

private

def add_body_class(new_class)
  @body_class ||= ""
  @body_class << " #{new_class}"
end

Then in your controller actions you can add a body class with:

add_body_class "two_col"

The reason for the add_body_class method is so that you can easily add multiple classes without worrying if you have already set the body_class instance variable.

I find this useful because quite often I will use a before filter to set a generic body class for every action in the controller...

before_filter :set_body_class

private
def set_body_class
  add_body_class "some_section_name"
end

To output @body_class replace your layout body tag with this:

<body<%= (@body_class.nil?) ? "" : " class='#{@body_class}'" %>>

That's basically a one line if statement that checks if @body_class exists before setting the class on the body tag.

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Comments...

• Why not move the
  bc. <%= (@body_class.nil?) ? "" : " class='#{@body_class}'" %>

  into a helper function?

  bc. def body_class
  return (@body_class.nil?) ? "" : " class='#{@body_class}'"
  end

  dstar at 01 May 08 at 09:05

• Well, that didn't work -- looks like block-code isn't supported by textpattern. Let me try it again:

  Why not move the

  <= (@body_class.nil?) ? ”” : ” class=’#{@body_class}’” >

  into a helper function?

  def body_class
  return (@body_class.nil?) ? ”” : ” class=’#{@body_class}’”
  end

  dstar at 01 May 08 at 09:08

• It's a fair point.

  If I was re-using it in multiple places (templates) I'd put it in a helper.

  For the purposes of keeping the tutorial simple I didn't.

  Paul Sturgess at 01 May 08 at 09:24

• Usefull post!

  Mark at 03 May 08 at 07:59

• Good post but I'll reiterate what dstar said: this should be in a helper. Unless, of course, your website is only 1 page, or you only require this functionality on-demand.

  This return would be more helpful:

  return (@body_class.nil?) ? " class='"#{[controller_name, action_name].join('-')}" : " class='#{@body_class}'"

  Damien at 16 Dec 11 at 15:54