ruby-on-rails – 为什么渲染json：返回NULL而不是boolean值

拒绝：可能与渲染json：internals有关？

这是我第一次看到这个巫术,所以请耐心等待.寻找好的答案:)

$curl -X GET -H localhost:3000/api/v1/alerts/1/show | python -m json.tool


{
    "body": "Deserunt laboriosam quod consequuntur est dolor cum molestias.","created_at": "2015-03-22T15:02:01.927Z","id": 1,"is_read": null,"subtitle": "Aspernatur non voluptatem minus qui laudantium molestiae.","title": "Et nemo magni autem similique consequuntur.","updated_at": "2015-03-22T15:02:01.927Z"
}

-一世

HTTP/1.1 200 OK
X-Frame-Options: SAMEORIGIN
X-Xss-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Content-Type: application/json; charset=utf-8
Etag: "3232ec2058ffb13db1f9244366fe2ea8"
Cache-Control: max-age=0,private,must-revalidate
X-Request-Id: c520cabe-6334-4997-956b-d1f21724b80c
X-Runtime: 0.016337
Server: WEBrick/1.3.1 (Ruby/2.1.2/2014-05-08)
Date: Sun,22 Mar 2015 15:28:21 GMT
Content-Length: 300
Connection: Keep-Alive

Rails控制台：

Alert.find(1)
  Alert Load (1.1ms)  SELECT  "alerts".* FROM "alerts"  WHERE "alerts"."id" = $1 LIMIT 1  [["id",1]]
=> #<Alert id: 1,title: "Et nemo magni autem similique consequuntur.",subtitle: "Aspernatur non voluptatem minus qui laudantium mol...",body: "Deserunt laboriosam quod consequuntur est dolor cu...",is_read: false,created_at: "2015-03-22 15:02:01",updated_at: "2015-03-22 15:02:01">

当我打电话给#to_json时会发生奇怪的事情

Alert.find(1).to_json
  Alert Load (4.1ms)  SELECT  "alerts".* FROM "alerts"  WHERE "alerts"."id" = $1 LIMIT 1  [["id",1]]
=> "{"id":1,"title":"Et nemo magni autem similique consequuntur.","subtitle":"Aspernatur non voluptatem minus qui laudantium molestiae.","body":"Deserunt laboriosam quod consequuntur est dolor cum molestias.","is_read":null,"created_at":"2015-03-22T15:02:01.927Z","updated_at":"2015-03-22T15:02:01.927Z"}"

当is_read为true时,也会发生这种情况.

更多信息：

Rails 4.1.7,Ruby 2.1.2,Postgresql

警报

create_table "alerts",force: true do |t|
  t.string   "title"
  t.string   "subtitle"
  t.text     "body"
  t.boolean  "is_read",default: false,null: false
  t.datetime "created_at"
  t.datetime "updated_at"
end

用于填充db的脚本：

Alert.populate 100 do |alert|
  alert.title = Faker::Lorem.sentence(3)
  alert.subtitle = Faker::Lorem.sentence(3)
  alert.body = Faker::Lorem.sentence(3)
  alert.is_read = false
end

控制器：

def show
  alert = Alert.find(params[:id])
  render json: alert
end

编辑2015年3月26日

irb(main):013:0> Alert.find(1)
  Alert Load (0.6ms)  SELECT  "alerts".* FROM "alerts"  WHERE "alerts"."id" = $1 LIMIT 1  [["id",title: "Test",subtitle: "waaat?",body: "heeeelp",created_at: "2015-03-26 15:49:32",updated_at: "2015-03-26 15:56:51">
irb(main):014:0> a.body
=> "heeeelp"
irb(main):015:0> a.title
=> "Test"
irb(main):016:0> a.is_read
=> nil
irb(main):017:0> a["is_read"]
=> false
irb(main):018:0> a.update_attributes(is_read: true)
   (0.4ms)  BEGIN
  SQL (0.5ms)  UPDATE "alerts" SET "is_read" = $1,"updated_at" = $2 WHERE "alerts"."id" = 1  [["is_read","t"],["updated_at","2015-03-26 15:57:26.645210"]]
   (2.1ms)  COMMIT
=> true
irb(main):019:0> a["is_read"]
=> true

最后：因为模型中有attr_reader：is_read.删除它将导致正确的序列化.有人可以解释一下吗？