Rails 4: check if a local variable exists and is true in a partial

Question

In a partial, I want to add a class only if the is_embedded local variable was passed in and is true. How can I check this?

Currently I check if is_embedded is true like this:

_some_partial.html.erb

<section 
  id="view-dashboard" 
  class="<%= "embedded" if is_embedded %>"
>

However this gives an error if is_embedded is not passed in: undefined local variable or method 'is_embedded'.

Do I always need to pass it in? Or is there a way I can check if it both exists and is true without having errors if it doesn't exist.

Answer 1

You can check the local_assigns hash, which includes the passed locals.

<section 
  id="view-dashboard" 
  class="<%= 'embedded' if local_assigns[:is_embedded] %>"
>

Answer 2

when rending the partial do this
<%= render partial: "some_partial", locals: {is_embedded: true} %>

#_some_partial.html.erb
<%
 #locals
 is_embedded ||= false
%>
<section
id="view-dashboard"
class="<%= "embedded" if is_embedded %>">hhd</section>

Answer 3

You can check this -

if defined?(is_embedded) && is_embedded

this will check if is_embedded defined and it is true