Can't modify frozen hash during validation

Rails
#1

hi

I’m working on an app where a user inputs their physical address. When
the form is submitted, we are using the USPS webservice to validate
the address and update the fields as necessary.

Code looks as follows:

Address < ActiveRecord::Base
def validate
usps_address_lookup
end

def usps_address_lookup
# call USPS service
# if error:
# errors.add_to_base usps_error.message
# else
# self.attributes = usps_address_attributes
# true
end
end

the issue is that I get an exception: “can’t modify frozen hash” where
I update the attributes on my Address.

If I move usps_address_lookup into before_save, it works unless I have
USPS validation errors which get completely ignored and the invalid
address gets saved.

relevant trace:

TypeError (can’t modify frozen hash):
/Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/
attribute_methods.rb:309:in []=' /Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/ attribute_methods.rb:309:inwrite_attribute_without_dirty’
/Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/
dirty.rb:132:in write_attribute' /Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/ attribute_methods.rb:211:incity=’
/Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/
base.rb:2361:in send' /Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/ base.rb:2361:inattributes=’
/Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/
base.rb:2360:in each' /Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/ base.rb:2360:inattributes=’
/app/models/address.rb:176:in usps_address_lookup' /app/models/address.rb:29:invalidate’
/Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/
validations.rb:930:in valid_without_callbacks?' /Library/Ruby/Gems/1.8/gems/activerecord-2.1.0/lib/active_record/ callbacks.rb:267:invalid?’

Any ideas? Thanks!

#2

spike grobstein wrote:

#   self.attributes = usps_address_attributes
#   true

end
end

the issue is that I get an exception: “can’t modify frozen hash” where
I update the attributes on my Address.

Perhaps the find of the record attached extra attributes
using a join.

–
We develop, watch us RoR, in numbers too big to ignore.

#3

We actually figured it out.

We have 2 calls to our function. One to look the address up and update
the fields from the USPS service and a second call which checks those
results and returns validation errors.

Not the best way of doing it, but at least it works.

#4

I am not sure if this is related to your problem, but it has the same
symptom “Can’t modify frozen hash”, so I put it here for other people to
refer if needed.

I have the error “Can’t modify frozen hash” when I query an array of
objects from the database, then do the following things:

  • Based on some conditions, I will update the array, or destroy objects
    in the array out of database, or add more objects to the array.

  • Save the objects in the array to the database.

The error happens when the code (with some logical bugs) deletes one of
the objects in the database, but still keeps the object in the array.
Later on, when saving the array, it saves that deleted object also, so
the error “Can’t modify frozen hash” happens.