http://stackoverflow.com/questions/998979/difference-between-and-in-rails/25617607#25617607
http://stackoverflow.com/questions/7996695/what-is-the-difference-between-and-in-erb-in-rails
<% %>Executes the ruby code within the brackets.
<%= %>Prints something into erb file.
<% -%>Avoids line break after expression.
<%# %>Comments out code within brackets; not sent to client (as opposed to HTML comments).
In Ruby 2.1 (not necessarily with Rails), the - removes one trailing newline:
- the newline must be the first char after the
> - no spaces are removed
- only a single newline is removed
- you must pass the
'-'option to use it
Examples:
require 'erb'
ERB.new("<%= 'a' %>\nb").result == "a\nb" or raise
begin ERB.new("<%= 'a' -%>\nb").result; rescue SyntaxError ; else raise; end
ERB.new("<%= 'a' %>\nb" , nil, '-').result == "a\nb" or raise
ERB.new("<%= 'a' -%>\nb" , nil, '-').result == 'ab' or raise
ERB.new("<%= 'a' -%> \nb" , nil, '-').result == "a \nb" or raise
ERB.new("<%= 'a' -%>\n b" , nil, '-').result == 'a b' or raise
ERB.new("<%= 'a' -%>\n\nb", nil, '-').result == "a\nb" or raise