Storing arrays in database using ActiveRecord

I am on rails 2.3.8 & I am using mysql as db adapter. I want to store arrays in my database. After searching I could come up with this very useful article.

Now I need to use GUI for input & not only server console. So say I have a text field called nums which logically should have int array. What shou开发者_开发问答ld be the format of nums so that it becomes easy to retrieve & store the array out of that string ?

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If you use serialize then you shouldn't have to worry about how the data is stored within the text field, although it's actually YAML.

serialize is documented in the Rails/ActiveRecord API (scroll down to the section headed "Saving arrays, hashes, and other non-mappable objects in text columns")

For display, you need a format that is understandable to users and that can be easily converted back into an array in your code. Comma- or space-delimited?

Formatting for output:

delim = ',' # or ' ' for spaces, or whatever you choose
array.join(delim)

Converting back into an array might work as follows:

num_array = nums.split(delim).map(&:to_i) # or to_f if not integers

or perhaps using String#scan?

num_array = nums.scan(/\d+/).map(&:to_i) # for positive integers

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If you're using postgres and rails 4, now you have a better native option.

# db/migrate/20140207133952_create_books.rb
create_table :books do |t|
  t.string 'title'
  t.string 'tags', array: true
  t.integer 'ratings', array: true
end
add_index :books, :tags, using: 'gin'
add_index :books, :ratings, using: 'gin'

# app/models/book.rb
class Book < ActiveRecord::Base
end

# Usage
Book.create title: "Brave New World",
            tags: ["fantasy", "fiction"],
            ratings: [4, 5]

## Books for a single tag
Book.where("'fantasy' = ANY (tags)")

## Books for multiple tags
Book.where("tags @> ARRAY[?]::varchar[]", ["fantasy", "fiction"])

## Books with 3 or more ratings
Book.where("array_length(ratings, 1) >= 3")

http://edgeguides.rubyonrails.org/active_record_postgresql.html