Ruby on rails 这其中有很多原因：联想出了问题？

预期结果：

Item.first.ratings

提供该项目的评分

所需的表和列：

item
  id,name,created_at,updated_at
ratings
  id,name,created_at,updated_at
item_ratings
  id,item_id,rating_id,value,created_at,updated_at

评级迁移：

class CreateRatings < ActiveRecord::Migration[5.0]
  def change
    create_table :ratings do |t|
      t.string :name
      t.references :user, foreign_key: true

      t.timestamps
    end
  end
end

class CreateJoinTableItemsRatings < ActiveRecord::Migration[5.0]
  def change
    create_join_table :items, :ratings do |t|
      t.index [:item_id, :rating_id]
      t.index [:rating_id, :item_id]
      t.string :value
    end
  end
end

问题:

---

这其中有很多原因：联想出了问题？这是要问的正确问题吗？

表

项目评分

不存在，但

项目评分

存在，请尝试将所有出现的

项目评分

重命名为

项目评分

是否尝试使用

重新加载来重新加载控制台是的，我做了多次，也退出和返回。检查了我出错的多个教程，但似乎都没有问题。这是正确的，您应该将
has\u many:item\u ratings
更改为
has\u many:items\u ratings
class Item < ApplicationRecord
   belongs_to :user
   has_many :item_ratings
   has_many :ratings, through: :item_ratings
end

class Rating < ApplicationRecord
  belongs_to :user
  has_many :item_ratings
  has_many :items, through: :item_ratings
end

class ItemRating < ApplicationRecord
  belongs_to :item
  belongs_to :rating
end

Item Load (0.7ms)  SELECT  "items".* FROM "items" ORDER BY "items"."created_at" DESC LIMIT $1  [["LIMIT", 1]]   
ActiveRecord::StatementInvalid: PG::UndefinedTable: ERROR:  relation "item_ratings" does not exist
    LINE 8:                WHERE a.attrelid = '"item_ratings"'::regclass
                                              ^
    :               SELECT a.attname, format_type(a.atttypid, a.atttypmod),
                         pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod,
                 (SELECT c.collname FROM pg_collation c, pg_type t
                   WHERE c.oid = a.attcollation AND t.oid = a.atttypid AND a.attcollation <> t.typcollation),
                         col_description(a.attrelid, a.attnum) AS comment
                    FROM pg_attribute a LEFT JOIN pg_attrdef d
                      ON a.attrelid = d.adrelid AND a.attnum = d.adnum
                   WHERE a.attrelid = '"item_ratings"'::regclass
                     AND a.attnum > 0 AND NOT a.attisdropped
                   ORDER BY a.attnum