如何通过关联在 has_many 下为一个参数播种多个 id

Question

一段时间以来，我一直在为这个应用程序的建模和初始种子过程苦苦挣扎。我想在Event 和Artist 之间制作一个联合表EventArtist，这样就可以检索任何活动阵容中的所有艺术家以及艺术家参加的所有活动。如何添加多个artist_ids 到一个事件？

这是种子文件：

venue = Venue.create(name: "Speakeasy", address: "Lynwood Ave", zip_code: "30312")
artist = Artist.create(name: "DJ Sliink", bio: "jersey club king")
artist2 = Artist.create(name: "DJ Spinn", bio: "Teklife's chief spokesperson")
#this is probably wrong
lineup = EventArtist.create({artist_id: artist.id}, {artist_id: artist2.id})

event = Event.create(name: "Dance your ass off", 
                      date: DateTime.new(2016,2,3,10,0,0,'+7'), 
                      venue: venue, 
                      #this right here... how?
                      artist_id: , 
                      description: "free free free")

这里是架构的相关部分

  create_table "event_artist", id: false, force: :cascade do |t|
    t.integer "artist_id"
    t.integer "event_id"
  end

  add_index "event_artist", ["artist_id"], name: "index_event_artist_on_artist_id", using: :btree
  add_index "event_artist", ["event_id"], name: "index_event_artist_on_event_id", using: :btree

  create_table "events", force: :cascade do |t|
    t.string   "name"
    t.datetime "date"
    t.text     "description"
    t.datetime "created_at",  null: false
    t.datetime "updated_at",  null: false
    t.integer  "venue_id"
  end

  add_index "events", ["venue_id"], name: "index_events_on_venue_id", using: :btree

型号：

class Event < ApplicationRecord
  belongs_to :venue
  has many :artists, through :event_artists
end

class EventArtist < ApplicationRecord
  belongs_to :event
  belongs_to :artist
end

class Artist < ApplicationRecord
  has_many :events, through: :event_artists
end

Answer 1

这里的问题是艺术家通过创建 EventArtists 与事件相关联，而不是通过将艺术家 ID 添加到事件。

首先，我们需要声明一个 Event 有 EventArtists。将 has_many :event_artists 添加到您的事件模型中。

在您的种子文件中，在创建事件时去掉 Artist_id。

event = Event.create(name: "Dance your ass off", 
                  date: DateTime.new(2016,2,3,10,0,0,'+7'), 
                  venue: venue, 
                  description: "free free free")

您可以通过创建 EventArtist 将艺术家与该事件相关联

EventArtist.create(event_id: event.id, artist_id: artist.id)

由于 rails 知道事件、event_artists 和艺术家之间的关联，因此以下所有内容都做同样的事情：

event.event_artists.create({artist_id: artist.id}, {artist_id: artist2.id})
event.event_artists.create({artist: artist}, {artist: artist2})
artist.event_artists.create({event_id: event.id})
artist.event_artists.create({event: event})

现在你可以做类似的事情

lineup = event.artists

- 或 -

artist_events = artist.events

Answer 2

您需要将其添加到两个模型中：

has_many :event_artists

模型是这样的：

class Event < ApplicationRecord
  belongs_to :venue
  has_many :artists, through: :event_artists
  has_many :event_artists
end

class EventArtist < ApplicationRecord
  belongs_to :event
  belongs_to :artist
end

class Artist < ApplicationRecord
  has_many :events, through: :event_artists
  has_many :event_artists
end

所以你可以播种：

event = Event.create(name: "Dance your ass off", 
                      date: DateTime.new(2016,2,3,10,0,0,'+7'), 
                      venue: venue, 
                      artists: [artist, artist2], 
                      description: "free free free")

或

event = Event.create(name: "Dance your ass off", 
                      date: DateTime.new(2016,2,3,10,0,0,'+7'), 
                      venue: venue,  
                      description: "free free free")
event.artists << artist
event.artists << artist2

两者都可以。祝你好运；）

Answer 3

您需要在 EventArtist 中为每位艺术家制作单独的记录。由于您有一个 has_many through 关联，这将允许您说 event.artists 并返回该事件中的所有艺术家。但是每个人都需要自己的 EventArtist 记录，其中包含一个 artist_id 和 event_id

您还需要在创建任何EventArtists 之前创建Event