DataMapper:解決関連クラスの作成時、idはnil

2186 ワード

require 'rubygems'
require 'data_mapper'

DataMapper.setup :default, "mysql://root:123456@localhost/cc"

class Url
  include DataMapper::Resource

  property :id, Serial
  property :original, String,:length => 255
  belongs_to :link
end


class Link
  include DataMapper::Resource

  property :id, Serial
  property :identifier, String
  property :created_at, Date
  has 1, :url
  has n, :visits

end

class Visit
  include DataMapper::Resource

  property :id, Serial
  property :created_at, Date
  property :ip, String
  property :contry, String
  belongs_to :link

end

DataMapper.auto_migrate!
DataMapper.finalize

url = Url.create(:original => "http://")
p url

#

関連クラスのオブジェクトを作成するときにsaveが行われていない場合、@idの値は通常nilですが、値が必要な場合があります.
解決策はbelongsでto後に、:required=>false

require 'rubygems'
require 'data_mapper'

DataMapper.setup :default, "mysql://root:123456@localhost/cc"

class Url
  include DataMapper::Resource

  property :id, Serial
  property :original, String,:length => 255
  belongs_to :link,:required => false
end


class Link
  include DataMapper::Resource

  property :id, Serial
  property :identifier, String
  property :created_at, Date
  has 1, :url
  has n, :visits

end

class Visit
  include DataMapper::Resource

  property :id, Serial
  property :created_at, Date
  property :ip, String
  property :contry, String
  belongs_to :link,:required => false

end

DataMapper.auto_migrate!
DataMapper.finalize

url = Url.create(:original => "http://")
p url

Mysqlストアド・プロシージャ・カーソルの例

Effective C++学習ノートの第4章(1)