Cloud9-RoR-關聯設計

參考文章：https://ihower.tw/rails4/activerecord.html

我的資料表關聯是這樣的

新增兩個model(原本的events在前面幾篇就建好了)

$ rails g model category cname:string status:boolean
$ rails g model event_category event_id:integer category_id:integer
$ bin/rake db:migrate

編輯app/models/event.rb

class Event < ActiveRecord::Base
  has_many :event_categories, ->{ order("category_id") }, :dependent => :delete_all
  has_many :categories, :through => :event_categories
end

編輯app/models/category.rb

class Category < ActiveRecord::Base
  has_many :event_categories, :dependent => :delete_all
  has_many :categories, :through => :event_categories
end

編輯app/models/event_category.rb

class EventCategory < ActiveRecord::Base
  belongs_to :event
  belongs_to :category
end

如此一來，三個資料表就關聯起來了。