我有一个简单的模型
class Interest < ActiveRecord::Base has_and_belongs_to_many :user_profiles end class UserProfile < ActiveRecord::Base has_and_belongs_to_many :interests end
UserProfile.joins(:interests).where('interests.id = ?',an_interest)
但是,我如何找到有多种兴趣的用户？当然,如果我这样做
UserProfile.joins(:interests).where('interests.id = ?',an_interest).where('interests.id = ?',another_interest)
我总是得到一个空结果,因为在连接之后,没有行可以同时具有interest.id = an_interest和interest.id = another_interest.
ActiveRecord中有没有办法表达“我想要有2个(指定)兴趣的用户列表？
更新(解决方案)这是我提出的第一个工作版本,对Omar Qureshi赞不绝口
specified_interests.each_with_index do |i,idx|
main_join_clause = "interests_#{idx}.user_profile_id = user_profiles.id"
join_clause = sanitize_sql_array ["inner join interests_user_profiles interests_#{idx} on
(#{main_join_clause} and interests_#{idx}.interest_id = ?)",i]
relation = relation.joins(join_clause)
end
解决方法
in(？)并不好 – 它是一个OR表达式
您需要做的是将多个连接写出来
profiles = UserProfile
interest_ids.each_with_index do |i,idx|
main_join_clause = "interests_#{idx}.user_profile_id = user_profiles.id"
join_clause = sanitize_sql_array ["inner join interests interests_#{idx} on
(#{main_join_clause} and interests_#{idx}.id = ?)",i]
profiles = profiles.join(join_clause)
end
profiles
您可能需要更改main_join_clause以满足您的需求.