def fetch_child(name, *args)
      raise NoSuchChildError.new("no child named #{name}") unless children.has_key?(name)
      children[name]
    end
def fetch_child(name, *args)
      raise NoSuchChildError.new("no child named #{name}") unless children.has_key?(name)
      children[name]
    end
Retrieves the component {Model} identified by the given <tt>name</tt>.

 @param name [String, Symbol] the component name
 @return [Model] the matching component
 @raise [NoSuchChildError] if name doesn't match any component