Rails Seralized My Object One Way & Refuses to Change

Rails
1

I have a rails class that serializes one attribute.

class Statistic < ActiveRecord::Base
  serialize :userlist
end

When a statistic object is loaded and it’s userlist changed from a
String to an Array userlist always gets serialized back into a String.
Objects that are properly deserialized into Arrays stay that way. The
framework seems to remember and deserialize :userlist into a String
even if it went in as an Array.

s = Statistic.find 238
=> #<Statistic id: 238, userlist: “— \n- 2222437\n- “99779”\n-
“120429”\n- “210503”\n- 32…”>

Note here: :userlist is an Array in YAML. Why doesn’t it get

correctly deserialized?

s.userlist.class
=> String

s.userlist = s.userlist.split(/\s+/)

s.userlist.class
=> Array

s.save
=> true

s.reload
=> #<Statistic id: 238,userlist: “— \n- 2222437\n- “99779”\n-
“120429”\n- “210503”\n- 32…”>

s.userlist.class
=> String

The goal of this exercise is to convert all String userlists to Array.
If I change the class (serialize :userlist, Array) before converting I
get TypeMismatch exceptions.

ActiveRecord::SerializationTypeMismatch: userlist was supposed to

be a Array, but was a String

Is there a way to force AR to interpret userlist as an Array?

% rails --version
Rails 2.3.4

2

Related, but doesn’t solve the problem:
http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/e548784faa7f9cef/c24380c98c64cbc3

3

Found the problem. The String is not correct YAML:

YAML::load(s.userlist)
ArgumentError: syntax error:ScannerException while scanning a quoted
scalar we had this found unexpected end of stream from (irb):8

The code from AR::B is

  def object_from_yaml(string)
    return string unless string.is_a?(String) && string =~ /^---/
    YAML::load(string) rescue string
  end

–Dean

4

This doesn’t explain why the userlist isn’t correctly serialized &
deserialized when reloaded…
–Dean

5

On Feb 26, 4:15 pm, Dean [email protected] wrote:

This doesn’t explain why the userlist isn’t correctly serialized &
deserialized when reloaded…

What’s the column type & how long is the data ? Is it getting
truncated because of the size of the column ?

Fred

6

This occurred to me too. The column type is text. I don’t recall the
length, but it was between 50,000 & 100,000 characters. I’ll check
the max_allowed_packet setting when I get back to work.

http://dev.mysql.com/doc/refman/5.0/en/blob.html

–Dean

On Feb 26, 11:38 am, Frederick C. [email protected]

7

On Feb 28, 11:42 am, Frederick C. [email protected]
wrote:

On Feb 28, 3:07 pm, Dean [email protected] wrote:

This occurred to me too. The column type is text. I don’t recall the
length, but it was between 50,000 & 100,000 characters. I’ll check
the max_allowed_packet setting when I get back to work.

Text columns have a 65535 limit (mediumtext and longtext columns can
take much more)

Fred

Thanks. That is the problem. 65535 characters on the nose.

–Dean

8

On Feb 28, 3:07 pm, Dean [email protected] wrote:

This occurred to me too. The column type is text. I don’t recall the
length, but it was between 50,000 & 100,000 characters. I’ll check
the max_allowed_packet setting when I get back to work.

Text columns have a 65535 limit (mediumtext and longtext columns can
take much more)

Fred