From: Jacob Fugal <lukfugl@...>
Date: 2006-09-14T05:13:24+09:00
Subject: Re: eRB <%=

On 9/13/06, Jason Roelofs <jameskilton@gmail.com> wrote:
> <% puts "Can't see me" %> --> nothing
>
> <%= puts "Can't see me" %> --> Can't see me

That's wrong. When rendering an ERB template, those two constructs
would be essentially equivalent. The both do the same thing: print
"Can't see me" to STDOUT and add nothing to the rendered output.

Using puts inside ERB does not put things into the rendered output --
it's not equivalent to PHP's echo/print. You should never need to use
puts or print within ERB (unless your intent is to print diagnostics
out to STDOUT while the ERB is being rendered).

<% %> and <%= %> both evaluate an expression. The difference is that
<%= %> includes the result of the expression (cast to a string using
to_s) in the rendered output. The result of the expression:

   puts "Can't see me"

is nil, since puts always returns nil. nil.to_s is an empty string, so
even with the <%= %> form, nothing is added to the rendered output.

What you want to do instead is just leave off the puts:

   Nothing added: <% "Can't see me" %>
   But printed here: <%= "Can see me" %>

Jacob Fugal