How to make field in model immutable after create

Hello everyone!

I want to have login field in User model which is set only once (on
create), and then it should fail validation if the value is changed.
How can I do this? I dig around for validation and tried

def after_validation_on_update
unless User.find_by_login(:login)
errors.add(:login, “is immutable. You can’t change it”)
end
end

in model, but somewhat it doesn’t work. Any hints on how can I make
field immutable after create?

Peace,
olegf

I’m almost positive there’s a better way, but you could try something
like this in the validate method of your model.

def validate

errors.add( :login, "Can't change your login details") if

self.login != User.find(self.id).login

end

Sorry there should be another line in that method

def validate
if not self.new_record?
errors.add( :login, “Can’t change your login details”) if
self.login != User.find(self.id).login
end
end

Yep, just do:

class User < ActiveRecord::Base
def login=(value)
# Either ignore the call, add an error, or raise an exception
end
end

Can you just override the default setter that active records creates in
your model and throw an execption if it gets called?


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----- Original Message ----
From: Oleg F. [email protected]
To: [email protected]
Sent: Monday, May 8, 2006 12:53:13 AM
Subject: [Rails] how to make field in model immutable after create

Hello everyone!

I want to have login field in User model which is set only once (on
create), and then it should fail validation if the value is changed.
How can I do this? I dig around for validation and tried

def after_validation_on_update
unless User.find_by_login(:login)
errors.add(:login, “is immutable. You can’t change it”)
end
end

in model, but somewhat it doesn’t work. Any hints on how can I make
field immutable after create?

Peace,
olegf

If you make it so that the setter method throws an exception/stops the
call,
how do you set the login when the record is first created?

Something along the lines of…

def login= (value)
if new_record?
self[:login] = value
else
raise “You can’t change login”
end
end

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