I use hstore with Postgres 9.2 and Rails 3.2 to store my object like this:
class User
user_hstore = {:user_id =>"123", :user_courses => [1,2,3]}
end
Now, when I retrieve user_courses, I get a string like this:
'[1, 2, 3]'
How do I convert this string to Rails array? Better yet, is there a way to store an array within a hstore object so that Rails will automatically retrieve it as array type?
JSON.parse "[\"1018\", \"1037\", \"1045\", \"1042\"]"
#=> ["1018", " 1037", " 1045", " 1042"]
Why not just use eval?
eval('[1, 2, 3]')
#=> [1, 2, 3]
Obviously, don't do this on arbitrary or user inputted data, but on an array of integers as you've displayed, it's perfectly safe.
To convert it to an array:
user_courses.gsub('[', '').gsub(']', '').split(",")
To make retrieval simpler, you can store it as a string by doing
user_hstore = {:user_id =>"123", :user_courses => '1,2,3'}
Just to throw another hat into the ring, this accomplishes the same as Vimsha's answer but is a little more short and sweet you could do:
"[1,2,3,4]"[1..-2].split(",")
which in your case could be:
user_courses[1..-2].split(",")
Edit: If speed is a concern I did a quick benchmark which can be found here. Doing only a few items is not a very big difference but 10,000 items + you can start seeing a difference. This is at 100,000 items:
# "[1,2,3,4]"[1..-2].split(",")
0.110000 0.000000 0.110000 ( 0.114739)
# "[1,2,3,4]".gsub("[", "").gsub("", "]").split(",")
1.080000 0.000000 1.080000 ( 1.081227)
serializeand hstore functionality, there isn't a readymade solution for this.