Join different querys in the same object

Hi, I'm new in Ruby on Rails and I don't know how can I achive something like this:

@switchs = Switch.find(:all)     for switch in @switchs       if current_user.shifts.count(:all,:conditions=>["date = ? and shift = ?",switch.destiny_date, switch.destiny_turn]) !=0         @valid = switch         @valid.merge(cambio)       end     end     return @valid

Let me explain. I just want to put in the same @valid object, switchs that satisfy the "if" condition. So, I have to loop for every switch and just select those ones that satisfy the condition. Is there any way to achieve this???

Thanks in advance.