Serializing a nested hash


K

Keith Tom

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...

Thanks in advance guys!
Keith
 
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R

Rick DeNatale

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.
 
C

Christoffer Lernö

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
 
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R

Rick DeNatale

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 }

So the OP could change this to:

attribute: {items: 2, date: 1}

On the other hand it might be nice to be able to use rails feature of
running things like these fixture yaml file's through erb/eruby first,
but that would require a facility (in the yaml module?) to produce an
inline yaml string.

--=20
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/
 

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