If your view looks like this:
<%= fields_for "events[]", event do |form| %>
<%= form.check_box :approved %>
<% end %>
then your params should contain a hash that looks like this (let's say event with id 29 is checked and event with id 23 is unchecked):
"events" => {"29" => {"approved" => "1"}, "23" => {"approved" => "0"}}
and your controller can save them like this:
events = params[:events]
events.each do |id, attrs|
event = Event.find(id)
event.update_attributes(attrs)
end
redirect_to admin_events_path