定义对另一个表中同一列的两个引用

问题描述：

我的项目中有一个团队表.我已经使用以下命令进行了应该创建表 Match 的迁移:

There's a Team table in my project. I've made a migration that is supposed to create table Match using the command below:

rails generate model Match Team:references Team:re
ferences score1:integer score2:integer date:datetime length:integer place:string

我希望我的 Matches 表包含 2 个引用 Teams 上相同列 (id) 的外键(team1、team2) 表.我很确定我做错了，因为在 schema.rb 中有:

I want my Matches table to contain 2 foreign keys (team1, team2) referencing same column (id) on Teams table. I'm pretty sure I did this wrong, because in schema.rb there's:

 create_table "matchs", force: true do |t|
    t.integer  "Team_id"
    t.integer  "score1"
    t.integer  "score2"
    t.datetime "date"
    t.integer  "length"
    t.string   "place"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  add_index "matchs", ["Team_id"], name: "index_matchs_on_Team_id"

而且我看不到第二个 Team_id.做我需要的正确方法是什么?

and I can't see 2nd Team_id. What is the proper way to do what I need?

答

一个数据库表不能有两列同名.这是您要使其工作所需要的.(我将使用 home_team 和 away_team 来帮助区分它们，但显然你可以使用 team1 和 team2>.)

A database table cannot have two columns with the same name. This is what you'll need in order to get this to work. (I'm going to use home_team and away_team to help distinguish them, but obviously you could use team1 and team2.)

rails g migration AddTeamsToMatch home_team_id:integer away_team_id:integer

这将生成如下所示的迁移:

This will generate a migration that looks like this:

class AddTeamsToMatch < ActiveRecord::Migration
  def change
    add_column :matches, :home_team_id, :integer
    add_column :matches, :away_team_id, :integer
  end
end

然后在您的 Team 模型中，您可以拥有以下内容:

Then in your Team model, you can have the following:

class Team < ActiveRecord::Base
  has_many :home_matches, class_name: "Match", foreign_key: "home_team_id"
  has_many :away_matches, class_name: "Match", foreign_key: "away_team_id"

  # Get all matches
  def matches
    self.home_matches + self.away_matches
  end
end

在您的 Match 模型中，您可以:

In your Match model, you can have:

class Match < ActiveRecord::Base
  belongs_to :home_team, class_name: "Team"
  belongs_to :away_team, class_name: "Team"

  # List both teams as array
  def teams
    [self.home_team, self.away_team]
  end
end

希望这会有所帮助.

定义对另一个表中同一列的两个引用

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