如何在创建时将数据传递给连接表

Question

我有以下结构：

class User < ActiveRecord::Base
  has_many :device_ownerships
  has_many :devices, :through => :device_ownerships
end

class Device < ActiveRecord::Base
  has_one :device_ownership
  has_one :user, :through => :device_ownership
end


class DeviceOwnership < ActiveRecord::Base
  belongs_to :user  
  belongs_to :device
end

但是 DeviceOwnership 也有 serial_number 行

我想在创建时将 serial_number 值传递给 DeviceOwnership。我知道我可以做类似的事情

def create
  user = User.create
  device = Device.create
  device_ownership = DeviceOwnership.create(:serial_numer => params[:device_serial_number], :device_id => device.id, :user_id => user.id)
end

这个好像不太优雅，不知道有没有更好的解决方案。

Answer 1

使用嵌套属性：

class User < ActiveRecord::Base

  has_many :device_ownerships
  has_many :devices, :through => :device_ownerships
  accepts_nested_attributes_for :devices
end

class Device < ActiveRecord::Base
  has_one :device_ownership
  has_one :user, :through => :device_ownership
  accepts_nested_attributes_for :device_ownership

  def device_ownership_attributes=(attributes)
    dev = build_device_ownership(attributes)
    dev.user = self.user
  end
end


class DeviceOwnership < ActiveRecord::Base
  belongs_to :user  
  belongs_to :device
end

如果您的参数如下所示，现在您可以在事务中一次保存所有关联：

pramas = {"user"=>{ "email"=>"user@example.com", "devices_attributes" =>{"0"=>{"name" => "Devise 1", "device_ownership_attributes"=>{"device_serial_number"=>"xyz"}}}}
user = User.create(params['user'])
# will save User, devise, and devise ownership all at once.