When we reuse the partial, there will be requirement to check whether the local variable in partial exists or not. We always introduce some variable for a race condition, which is needed to pass from one render location of many. Passing the default value for that variable in all the location you render the partial is tedious and error-prone.
Instead of this, checking whether the variable passed to the partial will work great and easy. But the catch is, you can’t use defined? opertator to do this. The ActionView documentation says its an implementation restriction.
So here is the way you can check whether the variable is available. Use local_assigns Hash.
<% if local_assigns.has_key? :name %>
<p><%= name %></p>
<% end %>
The local_assigns Hash contains all the locals you passed to the partial