Rails jbuilder将属性附加到现有的json

Question

我有一个如下所示的jbuilder模板：

json.flights @campaign.flights do |flight|
  json.partial! 'flights/show', collection: @campaign.flights, as: :flight

  json.has_delivered flight.has_delivered?
end

在尝试渲染has_delivered时渲染部分后抛出错误。 "can't convert String into Integer"

有谁知道如何渲染这个？