Extra whitespace around content_for value

730 Views Asked by Undistraction At 04 April 2025 at 12:20

I need to give my body tag a page-specific id to better target css selectors.

To this end I have set up the following in my application.erb layout:

<body id="<%= content_for :page_id %>">

Inside a page's view I can then do this:

<% content_for :page_id do %>
  <%='some-page-id'%>
<% end %>

The problem is that I am getting extra whitespace returned around the returned value resulting in the rendered body tag looking like this:

<body id="    some-page-id " >

This prevents the id from working. I have a workaround in place where I do this:

<% body_id = content_for :page_id %>
<body id="<%= body_id.strip %>">

But is there a way to fix this so that content_for returns its value without extra whitespace? What is causing this extra whitespace to be returned?

There are 5 best solutions below

Oscar Del Ben On 06 June 2012 at 15:02 BEST ANSWER

What is causing this extra whitespace to be returned?

The space

<% content_for :page_id do %>
  <%='some-page-id'%>
<% end %>

You could try this:

<%- content_for :page_id do -%>
  <%='some-page-id'%>
<%- end -%>

vicosanz On 06 June 2012 at 15:04

It's normal behaviour of Rails, I recommend you add "id=" inside content_for

<body "<%= content_for :page_id %>">

<% content_for :page_id do %>
  <%='id="some-page-id"' %>
<% end %>

Ted Kulp On 06 June 2012 at 15:05

You could always make it a one-liner with:

<body id="<%= content_for(:page_id).strip %>">

Undistraction On 06 June 2012 at 15:09

@OscarDelBen is correct:

This is what works:

<% content_for :page_id do %><%='some-page-id'%><% end %>

tight On 06 June 2012 at 15:49

Don't use extra ERB delimiters to set the content

<% content_for(:page_id) { "thepageid" } %>

You can go further and define a helper method

# in app/helpers/application_helper.rb
def page_id(page_id)
  content_for(:page) { page_id }
end

# in your template
<% page_id("thepageid") %>