Acces a binary column as a sequence of true/false flags

gem install has_blob_bit_field -v 1.1.1



A Rails extension to treat a binary column (blob) as a sequence of true/false flags (bits)

Example Usage

# Migration:
def change
	add_column :whatevers, :many_flags_blob, :binary

# Model:
class YourModel < ActiveRecord::Base
	has_blob_field :many_flags

# Usage:
o = YourModel.new
o.many_flags.size # => 0
o.many_flags.size = 666 # Can be as big as 8 times the binary limit of your column
o.many_flags[42] # => false
o.many_flags[42] = true
o.many_flags[700] # => IndexError
o.many_flags.count{|f| f} # => 1
o.many_flags = [false, true, true, false, false, false, false, true]
o.many_flags.map! {|f| !f}
o.many_flags == [true, false, false, true, true, true, true, false] # => true
o.many_flags_blob_changed? # => true


  • The convention is that your column has the same name as your accessing method with a '_blob' suffix, but you can specify the column to use when calling has_blob_field.

  • The blob is viewed as an array of bits where the first flag is stored using the highest bit of the first byte.

  • The size is always rounded up to a multiple of 8.

  • Targets: Ruby 2.0+, Rails 3.0+


Add this line to your application's Gemfile:

gem 'has_blob_bit_field'

And then execute:

$ bundle

Or install it yourself as:

$ gem install has_blob_bit_field


After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.


Bug reports and pull requests are welcome on GitHub at https://github.com/marcandre/has_blob_bit_field.


The gem is available as open source under the terms of the MIT License.