How to set current_user to the field

Suppose you want to track who created a project so you want to set current_user to the field user_id. You could do this in app/models/project.rb:

rails_admin do 
  edit do   
    field :user, :hidden do
      visible false
      default_value do
        bindings[:view]._current_user.id
      end
    end
  end 
end

This only hides the field and sets the default value, but this default value can be overriden in POST request which means it is not secure. So instead use your ability file to do this:

can :create, Project, user_id: user.id if user