Rails - HABTM关系 - 如何根据关联模型的属性查找记录

I have setup this HABTM relationship in the past and its worked before....Now it isnt and I'm at my wits end trying to figure out whats wrong. I've looking through the rails guides all day and cant seem to figure out what I'm doing wrong, so help would really be appreciated.I have setup this HABTM relationship in the pas