Question

我遇到了多对多关系的问题。我通过名为rtimespans的第三方建立了这种关系。

就像在教程中说的那样：

时间跨度模型：

class Timespan < ActiveRecord::Base

  validates :name, presence: true
  has_many :rtimespans
  has_many :subgroups, through: :rtimespans

  validates :start_h, presence: true
  validates :start_m, presence: true
  validates :end_h,   presence: true
  validates :end_m,   presence: true

  validate :e_must_be_0_60
  validate :e_must_be_0_24
  validate :s_must_be_0_60
  validate :s_must_be_0_24
  validate :e_bigger_s


    def e_must_be_0_60

        errors.add(:end_m,"must be 0-60") unless 0 < end_m.to_i
        errors.add(:end_m,"must be 0-60") unless 60 > end_m.to_i

    end

    def e_must_be_0_24

        errors.add(:end_h,"must be 0-24") unless 0 < end_h.to_i 
        errors.add(:end_h,"must be 0-24") unless 24 > end_h.to_i 

    end

    def s_must_be_0_60

        errors.add(:start_m,"must be 0-60") unless 0 < start_m.to_i
        errors.add(:start_m,"must be 0-60") unless start_m.to_i < 60

    end

    def s_must_be_0_24

        errors.add(:start_h,"must be 0-24") unless 0 < start_h.to_i
        errors.add(:start_h,"must be 0-24") unless start_h.to_i < 24

    end

    def e_bigger_s

        s=start_h.to_i*60+start_m.to_i
        e=end_h.to_i*60+end_m.to_i

        errors.add(:end_h,"End must be bigger than start") unless e > s

    end

end

rtimespan模型：

    class Rtimespan < ActiveRecord::Base
      belongs_to :timespan
      belongs_to :subgroup
      validates  :subgroup, presence: true
      validates  :subgroup, presence: true
    end

子组模型：

    class Subgroup < ActiveRecord::Base
  belongs_to :group

  has_many :timespans
  has_many :memberships
  has_many :users, through: :memberships

  has_many :translations
  has_many :actioncodes, through: :translations

  has_many :entries

  has_many :rules 

  validates :name, presence: true, uniqueness: true 
  validates :group_id, presence: true

   has_many :rtimespans
   has_many :timespans, through: :rtimespans
end

无论如何，当我想在这段关系上打电话时，我得到了这个错误。

ActiveRecord::StatementInvalid in Subgroups#show

Showing C:/xampp/htdocs/fluxcapacitor/app/views/subgroups/show.html.erb where line #40 raised:

SQLite3::SQLException: no such column: rtimespans.subgroup_id: SELECT "timespans".* FROM "timespans" INNER JOIN "rtimespans" ON "timespans"."id" = "rtimespans"."timespan_id" WHERE "rtimespans"."subgroup_id" = ?

任何人都可以告诉我，如何解决这个问题，或者至少告诉我，这个错误来自哪里？

Answer 1

我会检查错误指示的迁移。要查看是否存在缺失列，请检查您的schema.rb以确保该列存在

Answer 2

我假设错误是由于您在Subgroup模型中两次提到与 timespans 的关系。

您已定义

has_many :timespans  and 

has_many :timespans, through: :rtimespans

请在模型中更正并检查。

Answer 3

发现我的错误！我有一个“双ID ”：

  create_table "rtimespans", force: true do |t|
    t.integer "subgroup_id_id"
    t.integer "timespan_id_id"
  end

我创建了一个错误的迁移：

class CreateRtimespans < ActiveRecord::Migration
  def change
        create_table :rtimespans do |t|
            t.belongs_to :subgroup_id
            t.belongs_to :timespan_id
        end
    end 
end

应该是：

class CreateRtimespans < ActiveRecord::Migration
  def change
        create_table :rtimespans do |t|
            t.belongs_to :subgroup
            t.belongs_to :timespan
        end
    end 
end

没有这样的列，但列存在

3 个答案: