assign_attributes method not found


I am on an old version of Rails (3.0.5) and can’t upgrade right now. When I try to use assign_attributes on a model I get the error that the method is not found as below

NoMethodError - undefined method assign_attributes' for #<User:0x007ffb7c2ae638>: activemodel (3.0.5) lib/active_model/attribute_methods.rb:364:in method_missing’
activerecord (3.0.5) lib/active_record/attribute_methods.rb:46:in `method_missing’

I searched for the method in the classes where update_attributes is defined but indeed I couldn’t find assign_attributes defined in any of the gems. From the history of the method in the docs I understand it was created in 2.3.8 so I would think the method would be there in 3.0.5.

Any thoughts on why my ActiveRecord 3.0.5 gem doesn’t have this method defined?


Hi skt,

First of all: I would highly encourage you to upgrade immediately to at least 3.0.20.

Second: What method are you calling exactly to get that error?

Thanks Ryan.

I have a User model (using Devise/Omniauth) and I call the assign_attributes on an instance of User.

Part of what I am wondering is why isn’t there a definition of assign_attributes in the ActiveRecord::Base class in 3.0.5 that I am using.

Thanks for any insights/pointers.


since I see this a lot on the lists, it would be great if there were some easy place to see which versions of rails have security alerts against them. I know there’s this list here on rubygems but it doesn’t show which ones are insecure.

is that information easily found without having to dig through the security alerts?


You need to download a proper IDE my friend, like RubyMine (which I love, but there are others)

Specifically, you need to learn how to use the “Go to Declaration” feature of your IDE, which can give you that answer and take you directly to the part of ActiveRecord where that might be defined.

Hi Jason,

I actually use RubyMine and Command-B takes you to the declaration of function but since there is no declaration it tells me so. The same command takes me to the declaration of update_attributes when I try it on that and there is no assign_attributes function that I can find in 3.0.5.

Thanks for any pointers on why this function is not there in 3.0.5.


assign_attributes went away in the move from 2.3 -> 3.0, then re-appeared for 3.1.0. In 3.0.5, the closest equivalent is plain attributes=.

Regarding security updates, the best versions to use security-wise are always (in descending order of preference):

  • GREAT: the current release version (4.1.5 now, with 4.2 in beta)

  • OKAY: the most-recent release of the previous version (4.0.9)

  • KINDA NOT ENTIRELY BAD: the most-recent release of the any versions before that (3.2.19, 3.1.12, 3.0.20)

Older versions only get security updates, so the final releases in a particular line are almost always solving important security issues.

—Matt Jones

I have temporarily solved the problem (till I upgrade) with the following code in one of my libraries

class ActiveRecord::Base
def assign_attributes(attributes)
attributes.each_pair { |k, v| send("#{k}=", v) if respond_to?("#{k}=") } if attributes

If you see any issue with this in 3.0.5 then please provide feedback - seems to work ok. I got this code from a posting in one of the forums.


indeed… sorry I just get in the habit of helping newbies who do would do well to learn more advanced introspection/debegging techniques. My bad.

Maybe your method is defined as delegate :x, :to => :y ? I hate that those don’t work with Go-To-Declaration – really drives me nuts

If you still can’t find it, open up console, replace the object you are trying to introspect, and try @foo.method(:assign_attributes).source_location – that should tell you exactly where it is defined.