1.9.3p194 :002 > u = User.find_by_email("email@mail.ru")
1.9.3p194 :005 > u.addresses.size
=> 1
1.9.3p194 :006 > u.addresses.length
=> 1
1.9.3p194 :007 > u.addresses.count
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Rails 3.2.3中的大小,长度和计数没有区别,不是吗?