Question

Is it possible to pass in the value of a variable prior to it being passed to a helper method in Rails.

For example, I have a base64_encode helper method the @base_url is just being passed in a string literal instead of being evaluated.

<%= base64_encode(#{@base_url} + '/helloworld.html') %>

Answer 1

"#{ variable }" is variable interpolation in a ruby string. So you have at least two options for building your string.

<%= base64_encode("#{ @base_url }/helloworld.html") %>
# or
<%= base64_encode(@base_url + "/helloworld.html") %> 

Note that you need to use "" for Ruby string interpolation instead of ''.
Kansas City on Rails has a short blog post to see in a glance how string interplation can look like.