class Mustache::Context

def find(obj, key, default = nil)

Returns the value of key in obj if it is found and default otherwise.

key is not found.
default - An optional default value, to return if the
key - The key whose value you want.
obj - The object to perform the lookup on.

invokes that method. You get the idea.
If it's an object that responds to the key as a method call,
appropriate. If the object is a hash, does a simple hash lookup.
Finds a key in an object, using whatever method is most 
def find(obj, key, default = nil)
  if !obj.respond_to?(:to_hash)
    # If a class, we need to find tags (methods) per Parser::ALLOWED_CONTENT.
    key = key.to_s.tr('-', '_') if key.to_s.include?('-')
    if obj.respond_to?(key)
      meth = obj.method(key) rescue proc { obj.send(key) }
      meth.arity == 1 ? meth.to_proc : meth[]
    else
      default
    end
  elsif obj.has_key?(key)
    obj[key]
  elsif obj.has_key?(key.to_s)
    obj[key.to_s]
  else
    obj[key] || default
  end
end