我正在寻找一种方法来解决以下问题：
Event模型中的两个日期时间属性：
start_at: datetime end_at: datetime
我想使用3个字段以表格形式访问它们：
event_date start_time end_time
我遇到的问题是如何将实际和虚拟属性保持在“同步”,以便可以通过表单和/或直接通过start_at&更新模型. end_at.
class Event < ActiveRecord::Base
attr_accessible :end_at,:start_at,:start_time,:end_time,:event_date
attr_accessor :start_time,:event_date
after_initialize :get_datetimes # convert db format into accessors
before_validation :set_datetimes # convert accessors into db format
def get_datetimes
if start_at && end_at
self.event_date ||= start_at.to_date.to_s(:db) # yyyy-mm-dd
self.start_time ||= "#{'%02d' % start_at.hour}:#{'%02d' % start_at.min}"
self.end_time ||= "#{'%02d' % end_at.hour}:#{'%02d' % end_at.min}"
end
end
def set_datetimes
self.start_at = "#{event_date} #{start_time}:00"
self.end_at = "#{event_date} #{end_time}:00"
end
end
哪个有效：
1.9.3p194 :004 > e = Event.create(event_date: "2012-08-29",start_time: "18:00",end_time: "21:00") => #<Event id: 3,start_at: "2012-08-30 01:00:00",end_at: "2012-08-30 04:00:00",created_at: "2012-08-22 19:51:53",updated_at: "2012-08-22 19:51:53">
直到直接设置实际属性(end_at在验证时设置回end_time)：
1.9.3p194 :006 > e.end_at = "2012-08-30 06:00:00 UTC +00:00" => "2012-08-30 06:00:00 UTC +00:00" 1.9.3p194 :007 > e => #<Event id: 3,end_at: "2012-08-30 06:00:00",updated_at: "2012-08-22 19:51:53"> 1.9.3p194 :008 > e.save (0.1ms) BEGIN (0.4ms) UPDATE "events" SET "end_at" = '2012-08-30 04:00:00.000000',"start_at" = '2012-08-30 01:00:00.000000',"updated_at" = '2012-08-22 20:02:15.554913' WHERE "events"."id" = 3 (2.5ms) COMMIT => true 1.9.3p194 :009 > e => #<Event id: 3,updated_at: "2012-08-22 20:02:15"> 1.9.3p194 :010 >
我的假设是我还需要自定义“实际”属性的setter,但我不知道如何做到这一点w / out搞砸了默认行为.思考？也许有更多的“Rails-y”“回调-y”方式来处理这个问题？
解决方法
这是我的看法.我没有使用ActiveRecord测试它,但我留下了评论.希望这可以帮助.
class Event < ActiveRecord::Base
attr_accessible :end_at,:event_date
attr_accessor :start_time,:event_date
def start_time
@start_time || time_attr_from_datetime(start_at)
end
def start_time=(start_time_value)
@start_time = start_time_value
set_start_at
end
def end_time
@end_time || time_attr_from_datetime(end_at)
end
def end_time=(end_time_value)
@end_time = @end_time_value
set_end_at
end
def event_date
@event_date || start_at.to_date.to_s(:db)
end
def event_date=(event_date_value)
@event_date = event_date_value
set_start_at
set_end_at
end
def start_at=(start_at_value)
write_attribute(:start_at,start_at_value) # Maybe you need to do write_attribute(:start_at,DateTime.parse(start_at_value)) here ???
@start_time = time_attr_from_datetime(start_at)
end
def end_at=(end_at_value)
write_attribute(:end_at,end_at_value) # Maybe you need to do write_attribute(:end_at,DateTime.parse(end_at_value)) here ???
@end_time = time_attr_from_datetime(end_at)
end
private
def set_start_at
self.start_at = DateTime.parse("#{event_date} #{start_time}:00")
end
def set_end_at
self.end_at = DateTime.parse("#{event_date} #{end_time}:00")
end
def time_attr_from_datetime(datetime)
"#{'%02d' % datetime.hour}:#{'%02d' % datetime.min}"
end
end
编辑：获取和设置start_time和end_time有一个明确的模式.它可以通过元编程进行抽象,但我认为这会使示例不清楚.