我有一个具有很多会员资格的豁免对象.我想弄清楚豁免是否有特定季度的会员资格：
def has_current_membership?
memberships.count("begin_date >= :begin_date AND end_date <= :end_date",{ :begin_date => Time.Now.beginning_of_quarter,:end_date => Time.Now.end_of_quarter }).count > 0
end
然而,这给了我ArgumentError：未知密钥：begin_date.但是,成员资格有一个begin_date列,因为如果我在控制台中执行Waiver.first.memberships,我会得到：
[#<Membership id: 20,waiver_id: 1,begin_date: "2011-10-01",end_date: "2012-01-01",created_at: "2011-11-19 07:10:10",updated_at: "2011-11-19 07:10:10">]
我究竟做错了什么？
解决方法
您应该使用.where作为查找条件,而不是.count两次：
memberships.where("begin_date >= :begin_date AND end_date <= :end_date",:end_date => Time.Now.end_of_quarter }).count > 0
