ainame / activerecord-bit_field

activerecord-bit_field provide a feature of mapping bit fileds to RDB table in ActiveRecord.

Activerecord::BitField

Activerecord::BitField provides a feature of mapping bit fileds to RDB table in ActiveRecord. This is sort of reinventing the wheel. See See Also section.

Requirement

Ruby 2.1.0 or higher. This lib is using Array#to_h.

Installation

Add this line to your application's Gemfile:

gem 'activerecord-bit_field'

And then execute:

$ bundle

Or install it yourself as:

$ gem install activerecord-bit_field

Usage

0. Put require 'active_record/bit_field' if you don't use autoload
1. Define the integer column to using management of fields and create a migration file
2. Declare the bit_field in arbitrary models

class AddFilePermissionsTable < ActiveRecord::Migration
  def change
    create_table(:file_permissions) do |t|
      t.integer :file_id, null: false, default: 0 # you must specify `default: 0`
      t.integer :permission, null: false
    end
  end
end

...

class FilePermission < ActiveRecrod::Base
  include ActiveRecord::BitField

  # :read map to first bit, :write map to second, ....
  #
  # .. 0 0 0 0 | 0 0 0 0    <- permission column
  #                | | |
  #            +---+ | `-----+
  #            |     |       |
  #        execute write   read
  #
  bit_field permission: [:read, :write, :execute]
end

file_permission = FilePermission.new
file_permission.read? # => false in default

file_permission = FilePermission.create(file_id: 1, permission: 1) # `1` is the bit map value
file_permission.read? # => true
file_permission.write? # => false

file_permission.enable_write
file_permission.disable_read
file_permission.enable_execute
file_permission.save!

file_permission.permissin # => { read: false, write: true, execute: true }

Options

ActiveRecord::BitField can achieve default-true bit field easily. Normally, developers specify DEFAULT 0 to fields column, then "0" bit is supposed to represent false and "1" bit is supposed to represent true. If you want to use a single bit field which is true by default in a single column, perhaps, you may need to specify DEFAULT 1 in the table schema. Then there would be a problem. What if you want to add additional fields to that existing column? How can we prepare default values for rest of new bit fields?

ActiveRecord::BitField provides invert option. If you set true value with "invert" key, ActiveRecord::BitField deals with bit state oppositely; "0" bit behaves true and "1" bit behaves false.

class FilePermission < ActiveRecrod::Base
  include ActiveRecord::BitField

  bit_field permission: [:read, :write, :execute], invert: true
end

file_permisson = FilePermission.new
file_permisson.read? #=> true in default

See Also

You can use other products in the same need. This plugin doesn't have the select query each fields feature, but these have it.

• pboling/flag_shih_tzu
• grosser/bitfields

Contributing

1. Fork it ( https://github.com/ainame/activerecord-bit_field/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request