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
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#<Url @id=nil @original="http://" @link_id=nil>
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在创建关联类的对象时，没有进行save的时候，@id的值正常就是nil，但是有些时候需要它有值
解决办法是在belongs_to后面加上,:required => false
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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
?#<Url @id=1 @original="http://" @link_id=nil>
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