Using Rails serialize to save hash to database

The column type is wrong. You should use Text instead of String. Therefore, your migration should be:

 def self.up   add_column :users, :multi_wrong, :text end

Then Rails will properly convert it into YAML for you (and perform proper serialization). Strings fields are limited in size and will only hold especially-small values.

UPDATED:

Exact implementation will depend on your database, but PostgreSQL now has json and jsonb columns which can natively store your hash/object data and allow you to query against the JSON with ActiveRecord!

change your migration and you're done.

class Migration0001  def change    add_column :users, :location_data, :json, default: {}  endend

ORIGINAL:

For more details: rails docs && apidock

Make sure your column is :text and not :string

Migration:

$ rails g migration add_location_data_to_users location_data:text

should create:

class Migration0001  def change    add_column :users, :location_data, :text  endend

Your Class Would Look Like:

class User < ActiveRecord::Base  serialize :location_dataend

Available Actions:

b = User.newb.location_data = [1,2,{foot: 3, bart: "noodles"}]b.save

More Awesome?!

utilize postgresql hstore

class AddHstore < ActiveRecord::Migration    def up    enable_extension :hstore  end  def down    disable_extension :hstore  endend class Migration0001  def change    add_column :users, :location_data, :hstore  endend

With hstore you can set attributes on the serialized field

class User < ActiveRecord::Base    # setup hstore  store_accessor :location_data, :city, :stateend

Rails 4 has a new feature called Store, so you can easily use it to solve your problem. You can define an accessor for it and it is recommended you declare the database column used for the serialized store as a text, so there's plenty of room. The original example:

class User < ActiveRecord::Base  store :settings, accessors: [ :color, :homepage ], coder: JSONendu = User.new(color: 'black', homepage: '37signals.com')u.color                          # Accessor stored attributeu.settings[:country] = 'Denmark' # Any attribute, even if not specified with an accessor# There is no difference between strings and symbols for accessing custom attributesu.settings[:country]  # => 'Denmark'u.settings['country'] # => 'Denmark'