如何在Rails上使用Mongoid？

gem 'mongoid'

development:
  clients:
    default:
      database: my_database_name
      hosts:
        - localhost:27017
      options:
        read:
          mode: primary

rails g mongoid:model User

class User
  include Mongoid::Document
  field :name, type: String
  field :age, type: Integer
end

# 创建一个新的User对象
user = User.new(name: 'John Doe', age: 30)

# 保存User对象到MongoDB数据库
user.save

# 查询User对象
users = User.where(age: 30)

# 更新User对象
user.update(age: 31)

# 删除User对象
user.destroy

class User
  include Mongoid::Document
  field :name, type: String
  has_many :posts
end

class Post
  include Mongoid::Document
  field :title, type: String
  field :content, type: String
  belongs_to :user
end

class User
  include Mongoid::Document
  field :name, type: String
  field :age, type: Integer
  index({ name: 1 }, { unique: true })
end

# 查询年龄大于30的用户
users = User.where(:age.gt => 30)

# 查询名字为'John Doe'的用户
user = User.find_by(name: 'John Doe')