[Puppet Users] Referencing a variable from one class in another

I have one module, kibana, that defines a file snippet for the apache
module to fulfill (e.g., /etc/https/conf.d/kibana.conf). The apache::params
class defines a variable of the path of where this snippet should be
placed, $config_d. The snippet uses this variable in its definition.
However, it seems that the snippet never resolves the
$apache::params::config_d variable, and I'm guessing because the order of
instantiation isn't right. I've tried requiring the apache class from the
snippet, which seems it would enforce proper ordering, and I've tried
inheriting the kibana::apache class from apache::params. The former still
doesn't resolve and the latter throws an agent error. What is the proper
way for using a variable in one class in another class when
manifests/nodes.pp definitions of the classes can't be guaranteed?

Here are snippets of the class definitions I'm using:
http://pastie.org/5910079