hahcho / activerecord-column_metadata

ActiveRecord extension to store column metadata in database

ActiveRecord::ColumnMetadata

Store metadata about columns in the database, as comments on columns (advanced PostgreSQL feature)

Installation

Add this line to your application's Gemfile:

gem 'activerecord-column_metadata'

And then execute:

$ bundle

Or install it yourself as:

$ gem install activerecord-column_metadata

Usage

In a migration:

create_table(:cars) do |t|
  t.string :name
  t.string :manufacturer
  t.string :model

  t.boolean :4wd
  t.boolean :abs
  t.boolean :airbag
  t.boolean :gps
  t.boolean :music_player

  [:4wd, :abs, :airbag, :gps, :music_player].each do |extra|
    t.column_metadata(extra, {extra: true})
  end
end

or

add_column :cars, :aircondition, :boolean, metadata: {extra: true}

And then you can say in the model:

class Car < ActiveRecord::Base
  def self.extras
    ActiveRecord::JsonMetadata.to_a("cars").select do |arr|
      column_name, metadata = arr
      column_name if metadata["extra"] == true
    end
  end
end

Rationale

In the above example you could hardcode extras in the model:

class Car < ActiveRecord::Base
  def self.extras
    [:4wd, :abs, :airbag, :gps, :music_player]
  end
end

But what will happen when you have to add or remove an extra? You have to edit two files: migration and the corresponding ActiveRecord model. Unnecessary repetition causes brain injury.

Contributing

1. Fork it
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 new Pull Request