Question

In my model I have:

class Log < ActiveRecord::Base
serialize :data

...

def self.recover(table_name, row_id)
    d = Log.where(table_name: table_name, row_id: row_id).where("log_type != #{symbol_to_constant(:delete)}").last
    row = d.data

    raise "Nothing to recover" if d.nil?
    raise "No data to recover" if d.data.nil?

    c = const_get(table_name)
    ret = c.create(row.attributes)

end

And in my controller I calling it as:

def index
    Log.recover params[:t], params[:r]
    redirect_to request.referer
end

The problem is, if I access this page for the first time, I am getting error specified below, but after refresh, is everything OK. Where can be problem?

undefined method `attributes' for #<String:0x00000004326fc8>

In data column are saved instances of models. For the first time column isn’t properly unserialized, it’s just yaml text. But after refresh everything is fine. That’s confusing, what is wrong? Bug in rails?

It’s not every time, sometimes in first access everything is okey.

Answer 1

Deyamlizing an object of class Foo will do funny things if there is no class Foo. This can quite easily happen in development becauses classes are only loaded when needed and unloaded when rails thinks they might have changed.

Depending on whether the class is loaded or not the YAML load will have different results (YAML doesn’t know about rail’s automatic loading stuff)

One solution worth considering is to store the attributes hash rather than the activerecord object. You’ll probably avoid problems in the long run and it will be more space efficient in the long wrong – there’s a bunch of state in an activerecord object that you probably don’t care about in this case.

If that’s not an option, your best bet is probably to make sure that the classes that the serialized column might contain are loaded – still a few calls to require_dependency 'foo' at the top of the file.