Inject local variables into rails partial

Question

I want my partial below to get the classy class from it being injected through locals, but I keep getting undefined method for classy.

//view

<%= render layout: "layouts/partial", locals: {className: "classy"} do %>
...
<% end>

//partial

<div class="regular-div <%=className if className?%>"></div>

What do you mean? You are passing the local variable className and also referencing className. Are you sure this is not just a typo or sloppy error? — max
– max, Commented Dec 14, 2016 at 0:23
className is not getting into the partial as "classy". I want my div to get the class "classy" — stackjlei
– stackjlei, Commented Dec 14, 2016 at 0:24
It should be <%= className if local_assigns.has_key?(:className) %>. Since className and className? are not the same. local_assigns.has_key?(:className) is a way of safely checking if the local variable is set. — max
– max, Commented Dec 14, 2016 at 0:34

max · Accepted Answer · 2016-12-14 01:04:59Z

1

To check if a local variable is set use local_assigns.has_key?(:some_key) or local_assigns[:some_key] to safely access the local variable.

A nifty way of handling the common task of building a list of classes is:

module ApplicationHelper
  # Takes an array or list of classes and returns a string
  # Example:
  #  class_list('a', 'b', nil, 'c')
  #  => "a b"
  #  class_list(['a', 'b', nil, 'c'])
  #  => "a b c"
  def class_list(*classes)
    [*classes].flatten.compact.join(' ') 
  end
end

Then you can do:

<div class="<%= class_list('regular-div', local_assigns[:className]) %>"></div>

answered Dec 14, 2016 at 1:04

max

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