我有一个Rails 4 API。当用户在视图中搜索船只时,执行此方法会使所有船只与搜索过滤器匹配并使用渲染ActiveModel返回一个船模型数组作为json,并且:include和:仅限这样:
render :json => @boats, :include => { :mainPhoto => {:only => [:name, :mime]},
:year => {:only => :name},
# other includes...}
这很有效。
但是,除了这些信息,在视图中,我想显示船只的总数,例如“显示80艘船中的1至20艘”,因为有一个分页功能。所以,重点是我需要提供80艘船。我想避免发送两个执行几乎相同逻辑的请求,因此想法只运行一次searchBoats方法,并在结果中提供船只列表和变量numTotalBoats中的船只总数。我知道numTotalBoats不是船模型属性。所以,我认为它应该在渲染结果中包含一个自变量。就像是:
render :json => {boats: @boats with all the includes, numTotalBoats: @NumTotalBoats}
我尝试了数以千计的组合,但是我得到了语法错误,或者没有一个会返回预期的结果,例如
{boats: [boat1 with all the includes, boat2 with all the includes, ... boatN with all the includes], numTotalBoats: N}
没有添加任何宝石:
def index
boats = Boat.includes(:year)
render json: {
boats: boats.as_json(include: { year: { only: :name } }),
numTotalBoats: boats.count
}
end
但在某些时候,我相信你应该使用独立的序列化器:
注意:根据您是否使用分页gem,您可能需要将下面的.count
调用更改为.total_count
(对于Kaminari)或其他将从分页集合中正确读取计数的内容。
我建议使用ActiveModel Serializers,这就是你的情况如何实现。
首先将gem添加到Gemfile:
gem 'active_model_serializers', '~-> 0.10'
在config / initializers / active_model_serializer.rb中覆盖适配器:
ActiveModelSerializers.config.adapter = :json
为您的模型定义序列化程序,
# app/serializers/boat_serializer.rb
class BoatSerializer < ActiveModel::Serializer
attributes :name
has_one :year
end
# app/serializers/year_serializer.rb
class YearSerializer < ActiveModel::Serializer
attributes :name
end
最后,在你的控制器中:
boats = Boat.includes(:year)
render json: boats, meta: boats.count, meta_key: "numTotalBoats"
你会实现:
{
"boats": [
{
"name": "Boaty McBoatFace",
"year": {
"name": "2018"
}
},
{
"name": "Titanic",
"year": {
"name": "1911"
}
}
],
"numTotalBoats": 2
}
在每个索引控制器中添加该计数有点单调乏味,因此我通常最终定义自己的适配器或集合序列化程序,以便自动处理(使用Rails 5测试,而不是4)。
# lib/active_model_serializers/adapter/json_extended.rb
module ActiveModelSerializers
module Adapter
class JsonExtended < Json
def meta
if serializer.object.is_a?(ActiveRecord::Relation)
{ total_count: serializer.object.count }
end.to_h.merge(instance_options.fetch(:meta, {})).presence
end
end
end
end
# config/initializers/active_model_serializer.rb
ActiveModelSerializers.config.adapter = ActiveModelSerializers::Adapter::JsonExtended
# make sure to add lib to eager load paths
# config/application.rb
config.eager_load_paths << Rails.root.join("lib")
现在您的索引操作可能如下所示
def index
boats = Boat.includes(:year)
render json: boats
end
并输出:
{
"boats": [
{
"name": "Boaty McBoatFace",
"year": {
"name": "2018"
}
},
{
"name": "Titanic",
"year": {
"name": "1911"
}
}
],
"meta": {
"total_count": 2
}
}
我认为为不同的端点解析这个计数要容易一些,并且在使用集合进行响应时会自动获取它,因此您的控制器会更简单一些。