let enum select options use instance method

[leomao10]

I just create a report class like this:

  class ContactReport 
    include Datagrid

    datagrid_attribute :current_user
    datagrid_attribute :sites

    def initialize(current_user, attributes = {})
      super(attributes)
      self.current_user = current_user
      if current_user
        self.sites      = current_user.sites.active.doing_jsa
        scope do
          PsmContact.index_scope.restricted(sites).includes(:user)
        end
      end
    end
  end

and now I want to add a enum filter, and its select item should be current_user.sites

    filter(:site_id, :enum, :select => lambda { current_user.sites.flatten }, :prompt => "All sites") do |value|
      where(:site_id => value)
    end

However, I could not do that because the context for the lambda is ContactReport and it do not have a current_user methods.

Could be helpful if you can enable the select option to use current instance's method