问题
I have a has_many association between two models using a date as both the foreign and primary key for each model.
It works perfectly one way but not the other.
Works
has_one :quiz_log, :primary_key => :start_at, :foreign_key => :start_at
Doesn't work
has_many :event_logs, :primary_key => :start_at, :foreign_key => :start_at
The reason being (i think) because the start_at on QuizLog is a date and the start_at on EventLog is a datetime. So it returns nil trying to match the exact datetime on a simple date.
How can I cast the foreign_key start_at on the second statement to convert it first from datetime to simply date so it will match the second model?
回答1:
I'm not sure if you can do it without using finder_SQL, but this should work.
has_many :event_logs, :finder_sql => proc {
"SELECT * FROM event_logs WHERE DATE(event_logs.start_at) = '#{start_at}'"
}
回答2:
After reading the title twice, I understand what you are asking for. May be something like the following would work?:
has_many :event_logs, :primary_key => :start_at, :conditions => proc { "start_date = '#{event_logs.start_date.to_date}'" }
回答3:
I'm not sure but I would use something like:
def event_logs
EventLogs.where('event_logs.start_at >= ? AND event_logs.start_at < ?', start_at, start_at + 1.day)
end
来源：https://stackoverflow.com/questions/17436829/has-many-conditions-or-proc-on-foreign-key