On Mar 23, 2007, at 21:23 , Rick DeNatale wrote:

> On 3/23/07, Keith Tom <keith.tom / gmail.com> wrote:
>> Hi all,
>>
>> I ran into some trouble w/ a model that has a nested hash  
>> attribute and
>> need some help.
>> Here are the details:
>>
>> - migration has "t.column :attribute, :text"
>> - model has "serialize :attribute, Hash"
>>
>> Now when I put a plain (non-nested) hash in my fixtures, this  
>> attribute
>> works fine; I run the tests, it unserializes, and am very happy.
>> When I put something like this in the fixture:
>>
>>     attribute: "<%= { :date => 1, :items => 2}.to_yaml %>"
>>
>> I run the tests and get:
>>
>> Exception: attribute was supposed to be a Hash, but was a String
>> /usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4.5618/lib/ 
>> active_record/base.rb:1951:in
>> `unserialize_attribute'
>>
>> I checked and the string that is being returned is:
>>
>> ---  :items: 2 :date: 1
>>
>> I did some googling and was under the impression nested hashes are
>> okay...  I get the feeling that is wrong...
>
> You can't nest yaml that way, nesting is indicated by indention, and
> the --- indicates the start of a yaml document:
>
> irb(main):005:0> {:attribute => {:date => 1, :items => 2}}.to_yaml
> => "--- \n:attribute: \n  :items: 2\n  :date: 1\n"
>
> irb(main):006:0>  puts ({:attribute => {:date => 1, :items =>  
> 2}}.to_yaml)
> ---
> :attribute:
>  :items: 2
>  :date: 1
> => nil
>
>
> Not sure what the solution is, but I think that's the problem.

If one wants to put a hash (or an array) on a single line with yaml,  
you need to use the {} / [] format.

So this:
---
:attribute:
  :items: 2
  :date: 1

Can be written
:attribute: { :items: 2, :date: 1 }

I.e.

YAML::load(":attribute: { :items: 2, :date: 1 }")
=> {:attribute=>{:items=>2, :date=>1}}

YAML::load("---\n:attribute:\n  :items: 2\n  :date: 1")
=> {:attribute=>{:items=>2, :date=>1}}


/Christoffer