新手问题 mongoid 获取结果集出现奇怪的问题~~~ 求支招!
我有两个 model, Topic 和 User 如下
class Topic
include Mongoid::Document
include Mongoid::Timestamps
field :title
field :content
belongs_to :user
end
class User
include Mongoid::Document
field :username
has_many :topics, inverse_of: :user
end
现在我希望获取最后 10 条 Topic 的记录，并显示作者的用户名: topics = Topic.desc(:created_at).limit(10) topics.each do |topic| topic.user.username #报错 end
topic.user.username 这句报错 :( 错误为：undefined method `username' for nil:NilClass
topic.user 怎么会为 nil 呢？求解！ (另外如果将查询改为 where 查询就没问题，topics = Topic.where(XXXXX) 这样就不会报错.)
mongoid 官方给你的例子，我也不太熟悉你看一看
class Artist
include Mongoid::Document
field :name, type: String
embeds_many :instruments
end
class Instrument
include Mongoid::Document
field :name, type: String
embedded_in :artist
end
syd = Artist.where(name: "Syd Vicious").between(age: 18..25).first
syd.instruments.create(name: "Bass")
syd.with(database: "bands", session: "backup").save!
hhuai
#6
2013年04月23日
测了一下，没有问题
require('mongoid')
Mongoid.load!("./mongoid.yml",:development)
class Topic
include Mongoid::Document
include Mongoid::Timestamps
field :title
field :content
belongs_to :user
end
class User
include Mongoid::Document
field :username
has_many :topics, inverse_of: :user
end
user = User.create({username: 'test'})
Topic.create({title: 'topic', content:"content", user:user})
topics = Topic.desc(:created_at).limit(10)
topics.each do |topic|
puts topic.user.username #报错
end
输出 test, 可能你录数据没录好，没对应到 user. mongo 就是不太严格。
