Can I save as Model's property as a hash?

Question

I want to do the following.

I want my model to have a column that store's a hash i.e. name/value pairs. When I load a record in my model, I don't want it to parse to de-seralize the value from the database UNLESS I access it i.e. lazy initialization.

This is b/c only a few percentage of my rows in the db will have values for the hash, and they will rarely be accessed.

Is this possible?

example usage:

user.properties["age"] = 12

user.properties["height"] = xxx

user.save

I'm not sure how it would be saved into the db, maybe in json format?

That is not what [hash](http://en.wikipedia.org/wiki/Hash_function) means — BlueRaja - Danny Pflughoeft, Mar 06 '11 at 20:20

vise · Answer 1 · 2011-03-06T20:41:19.103

5

Yes, you can serialize the data.

An excerpt from http://api.rubyonrails.org/classes/ActiveRecord/Base.html:

class User < ActiveRecord::Base
  serialize :preferences
end

user = User.create(:preferences => { "background" => "black", "display" => large })
User.find(user.id).preferences # => { "background" => "black", "display" => large }

edited Mar 06 '11 at 20:41

answered Mar 06 '11 at 20:22

vise

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but this property will be de-serialized each time I load the object right? I want it lazy-de-serialized i.e. only if accessed – Blankman Mar 07 '11 at 16:30

Unixmonkey · Answer 2 · 2011-03-06T21:16:35.717

1

ActiveRecord::Base#serialize Does just this.

class User < ActiveRecord::Base
  serialize :preferences, Hash
end

user = User.create(:preferences => { "background" => "black", "display" => large })
User.find(user.id).preferences # => { "background" => "black", "display" => large }
User.find(user.id).preferences[:background] # => "black"

edited Mar 06 '11 at 21:16

answered Mar 06 '11 at 20:24

Unixmonkey

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I stand corrected as I pasted the wrong excerpt, but you should have mentioned that in a comment. After posting just a link, then editing your post with the good excerpt and emphasising my mistake in your answer I can't help of finding the new recent edits that don't get saved process unfair. – vise Mar 06 '11 at 20:40
Good point. It would have been more tactful to comment on your almost correct answer. Sorry, It's no excuse, but I'm still new to StackOverflow and learning the ropes. I just want to help out fellow Rubyists. – Unixmonkey Mar 06 '11 at 21:31

score 0 · Answer 3 · edited May 23 '17 at 12:15

0

it is worthy to add that for proper serialization the preferences column should have type of Text, see Using Rails serialize to save hash to database

edited May 23 '17 at 12:15

Community

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answered Apr 14 '12 at 11:22

zeliboba7

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score 0 · Answer 4 · answered Mar 06 '11 at 21:24

0

You can use a string as a data type, and save it the hash in yaml format. You need to load this yaml string, but IMHO gives you more portability.

hash = {a => b, c=>d}
object.properties = hash.to_yaml
.
.
.
hash = Yaml::load(object.properties)

answered Mar 06 '11 at 21:24

Gareve

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Can I save as Model's property as a hash?

4 Answers4