ActiveRecord :: HasManyThroughOrderError：不能具有has_many：through关联

Danil Panshin 发表于 Dev

丹尼尔·潘欣（Danil Panshin）

在我的Rails应用程序中，我正在尝试创建一个系统，该系统将向用户奖励各种成就的徽章

创建了一个表“ user_badges”

移民：

class CreateUserBadges < ActiveRecord::Migration[5.1]
  def change
    create_table :user_badges do |t|

    t.references :user, foreign_key: true
    t.references :badge, foreign_key: true

    t.timestamps
    end
  end
end

型号UserBadge：

class UserBadge < ApplicationRecord

  belongs_to :user
  belongs_to :badge

end

徽章型号：

class Badge < ApplicationRecord
  has_many :users, through: :user_badges
  has_many :user_badges
end

模型用户：

class User < ApplicationRecord
  ...

  has_many :badges, through: :user_badges
  has_many :user_badges

  ...
end

当我尝试向用户添加徽章时：

b = Badge.create(title: 'first')

User.last.badges << b

我收到此错误：

ActiveRecord::HasManyThroughOrderError: Cannot have a has_many 
:through association 'User#badges' which goes through 
'User#user_badges' before the through association is defined.

当我简单地打电话给：

User.last.badges

同样的错误：

ActiveRecord::HasManyThroughOrderError: Cannot have a has_many 
:through association 'User#badges' which goes through 
'User#user_badges' before the through association is defined.

维沙尔泰姬陵

has_many首先定义关联，然后添加through:关联

class UserBadge < ApplicationRecord
  belongs_to :user
  belongs_to :badge
end

class Badge < ApplicationRecord
  has_many :user_badges # has_many association comes first
  has_many :users, through: :user_badges #through association comes after
end


class User < ApplicationRecord
  ...
  has_many :user_badges
  has_many :badges, through: :user_badges
  ...
end

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