Ruby on rails: virtual method that modifiyng model attributes with help of << couldn't save that attribute
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30-09-2019 - |
문제
There is model Ratification with attribute comment (of type text)
def Ratification < ActiveRecord::Base
attr_accessor :add_comment
def add_comment=(text)
self.comment ||= ""
self.comment << "\r\n" + text
end
end
And if I use add_comment= it is ok before I save the object. After save comment changes was dropped.
>> r = Ratification.last
Ratification Load (0.6ms) SELECT * FROM `ratifications` ORDER BY ratifications.id DESC LIMIT 1
=> #<Ratification id: 8, user_id: 686, comment: "dasads", created_at: "2010-06-25 13:16:24", updated_at: "2010-06-25 13:38:36">
>> r.comment
=> "dasads"
>> r.add_comment="text"
=> "text"
>> r.comment
=> "dasads\r\ntext"
>> r.save
SQL (0.7ms) BEGIN
SQL (0.2ms) COMMIT
=> true
>> r.reload
Ratification Load (1.6ms) SELECT * FROM `ratifications` WHERE (`ratifications`.`id` = 8)
=> #<Ratification id: 8, user_id: 686, comment: "dasads", created_at: "2010-06-25 13:16:24", updated_at: "2010-06-25 13:38:36">
>> r.comment
=> "dasads"
Why?!
Rails 2.3.8 Ruby 1.8
해결책
Hrrrm...that IS weird, I'm seeing similar behavior from my rails app when I try to do:
@s.name << "test"
and then reload...the original name is getting reset!
HOWEVER, if I do @s.name += "test"
then even after reloading, the new name is saved.
I'm not sure why << is behaving like that, but I usually default to += in all cases, so I've never noticed it before. Does changing to += help you?
Edit: Looking at the API, maybe it's because << modifies the original string, whereas + or += makes a NEW string, that contains the old one? Maybe rails somehow only saves things that it has marked as new (rather than modified?)