%input{:name => "post[my_card_ids][]", :type => "hidden",value: "#{post["my_card_ids"]}",id: "my_card_ids"}

<input id="my_card_ids" name="post[my_card_ids][]" type="hidden" value="[5d1b83a6616b6523a9020000, 5d1b9893616b653abd0b0000]">

<ActionController::Parameters {"my_card_ids"=>["["5d1b83a6616b6523a9020000", "5d1b9893616b653abd0b0000"]"]