Rails ActiveRecord 关联问题

Question

我有 2 个模型：

Performance 和 PerformanceType 以及 2 个各自的表：performances 和 performance_types。

进入performances有一个外键列“performance_type_id”。

如何使用 ActiveRecord 关联从另一个表中获取 performance_type_id 的名称？

class Performance < ActiveRecord::Base
has_one :users
has_one :rates
has_one :performace_types
end

class PerformanceType < ActiveRecord::Base
    belongs_to :performances
end

使用上面的代码我尝试在控制台中做：

myvar = Performance.first
myvar.performance_types
NoMethodError: undefined method `performance_types' for #<Performance:0x007f9694b3e700>

我知道问题出在我对活动记录关联的错误解释上，谁能帮助我？

问候。

从创建到添加外键的迁移...

class CreatePerformances < ActiveRecord::Migration
  def change
    create_table :performances do |t|

      t.timestamps null: false
    end
  end
end

class CreatePerformanceTypes < ActiveRecord::Migration
  def change
    create_table :performance_types do |t|

      t.timestamps null: false
    end
  end
end

class AddPerformanceTypeIdToPerformance < ActiveRecord::Migration
  def change
    add_column :performances, :performance_type_id, :integer
  end
end

class AddAppointmentInfoToPerformance < ActiveRecord::Migration
  def change
    add_column :performances, :user_id, :integer
    add_column :performances, :start_at, :datetime
    add_column :performances, :end_at, :datetime
  end
end

class AddUserToPerformances < ActiveRecord::Migration
  def change
    add_foreign_key :performances, :users
  end
end

class AddTypeToPerformances < ActiveRecord::Migration
  def change
    add_foreign_key :performances, :performance_types
  end
end

class AddAdditionalFieldsToPerformanceType < ActiveRecord::Migration
  def change
    add_column :performance_types, :name, :string
    add_column :performance_types, :description, :string
  end
end

class AddPerformanceTypeToRate < ActiveRecord::Migration
  def change
    add_foreign_key :rates, :performance_types
  end
end

class AddRateToPerformances < ActiveRecord::Migration
  def change
    add_column :performances, :rate_id, :integer
    add_foreign_key :performances, :rates
  end
end

Answer 1

has_one 和 belongs_to 指的是单个对象，因此您应该使用单数形式

class Performance < ActiveRecord::Base
    has_one :users
    has_one :rates
    has_one :performance_type
end

class PerformanceType < ActiveRecord::Base
    belongs_to :performance
end

Answer 2

我认为这就是你想要的。外键 performance_type_id 保留在性能中。您有许多具有相同表演类型的表演，但每个表演只有一种表演类型。

class Performance < ActiveRecord::Base 
  # note performance type is singular
  belongs_to :performance_type
end

class PerformanceType < ActiveRecord::Base
  has_many :performances 
end

p = Performance.first
# this should work 
p.performance_type

Answer 3

您应该更改 Performance 类，列出与单数模型（不是复数）的“has_one”关系：

class Performance < ActiveRecord::Base
  has_one :user
  has_one :rate
  has_one :performance_type
end

class PerformanceType < ActiveRecord::Base
  belongs_to :performance
end

正确配置迁移文件也很重要：

class CreatePerformances < ActiveRecord::Migration
  def change
    create_table :performances do |t|
    end

    create_table :performance_types do |t|
      t.belongs_to :performance, index: true
      t.belongs_to :rate
      t.belongs_to :user
    end
  end
end