Question

这有点复杂，我不知道如何实现它。我有一个用户模型和一个关系模型。用户可以“跟随”彼此（就像推特一样）。关系模型设置正确，效果很好。

接下来，我有一个事件模型。每个用户has_and_belongs_to_many事件（用户和事件之间的多对多关联）。用户“参加”活动。

我想要做的是列出所有

事件的列表

由current_user
。

如果可能，我希望通过用户模型访问此列表，以便我可以说current_user.event_feed，它将列出上述所有事件。

以下是我的模特：

class Event < ActiveRecord::Base
  attr_accessible :name, 
                  :description, 
                  :event_date, 
                  :location, 
                  :owner_id,
                  :category,
                  :photo

  CATEGORIES = ['Music', 'Outdoors', 'Party']

  has_and_belongs_to_many :users

和关系模型：

class Relationship < ActiveRecord::Base
  attr_accessible :followed_id

  belongs_to :follower, :class_name => "User"
  belongs_to :followed, :class_name => "User"

  validates :follower_id, :presence => true
  validates :followed_id, :presence => true
end

和用户模型：

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :token_authenticatable, :encryptable, :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  attr_accessible :email, :password, :password_confirmation, :remember_me
  attr_accessor :password
  attr_accessible :name, :email, :password, :password_confirmation, :time_zone

  has_and_belongs_to_many :events

  has_many :relationships, :dependent => :destroy,
                             :foreign_key => "follower_id"
  has_many :reverse_relationships, :dependent => :destroy,
                                   :foreign_key => "followed_id",
                                   :class_name => "Relationship"
  has_many :following, :through => :relationships, 
                       :source  => :followed
  has_many :followers, :through => :reverse_relationships,
                       :source  => :follower

谢谢！

Answer 1

活动模型：

scope :attended, where("event_date < #{Date.today}")

用户模型：

# Returns collection of events that are attended by user and users she follows
def attended events
  attended_events = []
  attended_events << events.attended
  followers.each do |follower|
    attended_events << follower.events.attended
  end
  attended_events
end

Answer 2

1) being attended by the current_user and 只需拨打current_user.events

即可实现此目的

2) are being attended by users that current_user is following. 这有点棘手。您希望最终得到其他用户事件的扁平列表：current_user.following.collect { |friend| friend.events }.flatten #=> returns an array of followers' events

由于您希望在单个列表中显示所有事件（从我可以收集的内容），我认为演示者类很有用：

class EventFeed
    attr_accessor :event, :display_name

   def initialize(event, name)
     self.event = event
     self.name  =  name
   end
end

现在，将它们添加到current_user.event_feed

class User
   def event_feed; []; end
end

并将它们粘合在一起：

current_user.events.each { |e| current_user.event_feed << EventFeed.new(e, 'YOU') }
current_user.following.each do |friend| 
   friend.events.each { |e| current_user.event_feed << EventFeed.new(e, friend.name) }
end

current_user.event_feed #=> an array of EventFeed objects where you can display "You are going to #{event.name}"

当然这是伪代码，但它应该让你走上正确的轨道

Answer 3

这只是rails 3，但相当优雅（未经测试，希望我对habtm关系的记忆是可以的）。

class User < ActiveRecord::Base
  # ...

  def event_feed
    ids = self.followers.collect(&:id) << self.id
    Event.includes(:users).where(["`users`.id IN (#{ids.join(',')})"])
  end

  # ...
end

如何通过与其他模型（用户）的关系来提取模型（事件）列表？

3 个答案: