ConfigFor::DataModel

A minimal, ActiveRecord::QueryMethods-like interface for data models backed by Rails configuration files.

Motivation

Not all of your application's data must reside in the database. For example, States & Countries don't change very often and don't need to be editable by users.

Rails provides a mechanism for loading such data from YAML files in your application's config directory:

Rails.application.config_for(:filename)

This is useful on it's own, but I've found myself abstracting ontop of this Rails feature often enough that I decided to extract it for reuse.

Usage

Let's say we have a YAML file with Country & State Data like the following.

e.g. /config/countries.yml

shared:
  -
    id: AU
    name: Australia
    states:
      -
        id: ACT
        name: Australian Capital Territory
        country_id: AU
      -
        id: NSW
        name: New South Wales
        country_id: AU
      -
        id: NT
        name: Northern Territory
        country_id: AU
      -
        id: QLD
        name: Queensland
        country_id: AU
      -
        id: SA
        name: South Australia
        country_id: AU
      -
        id: TAS
        name: Tasmania
        country_id: AU
      -
        id: VIC
        name: Victoria
        country_id: AU
      -
        id: WA
        name: Western Australia
        country_id: AU
  -
    id: CA
    name: Canada
    states:
      -
        id: AB
        name: Alberta
        country_id: CA
      -
        id: BC
        name: British Columbia
        country_id: CA
      -
        id: MB
        name: Manitoba
        country_id: CA
      -
        id: NB
        name: New Brunswick
        country_id: CA
      -
        id: NL
        name: Newfoundland
        country_id: CA
      -
        id: NS
        name: Nova Scotia
        country_id: CA
      -
        id: NT
        name: Northwest Territories
        country_id: CA
      -
        id: NU
        name: Nunavut
        country_id: CA
      -
        id: 'ON' # in YAML, unquoted 'ON' is treated as boolean true
        name: Ontario
        country_id: CA
      -
        id: PE
        name: Prince Edward Island
        country_id: CA
      -
        id: QC
        name: Quebec
        country_id: CA
      -
        id: SK
        name: Saskatchewan
        country_id: CA
      -
        id: YT
        name: Yukon
        country_id: CA
  -
    id: US
    name: United States
    states:
      -
        id: AL
        name: Alabama
        country_id: US
      -
        id: AK
        name: Alaska
        country_id: US
      -
        id: AZ
        name: Arizona
        country_id: US
      -
        id: AR
        name: Arkansas
        country_id: US
      -
        id: CA
        name: California
        country_id: US
      -
        id: CO
        name: Colorado
        country_id: US
      -
        id: CT
        name: Connecticut
        country_id: US
      -
        id: DE
        name: Delaware
        country_id: US
      -
        id: DC
        name: District of Columbia
        country_id: US
      -
        id: FL
        name: Florida
        country_id: US
      -
        id: GA
        name: Georgia
        country_id: US
      -
        id: HI
        name: Hawaii
        country_id: US
      -
        id: ID
        name: Idaho
        country_id: US
      -
        id: IL
        name: Illinois
        country_id: US
      -
        id: IN
        name: Indiana
        country_id: US
      -
        id: IA
        name: Iowa
        country_id: US
      -
        id: KS
        name: Kansas
        country_id: US
      -
        id: KY
        name: Kentucky
        country_id: US
      -
        id: LA
        name: Louisiana
        country_id: US
      -
        id: ME
        name: Maine
        country_id: US
      -
        id: MD
        name: Maryland
        country_id: US
      -
        id: MA
        name: Massachusetts
        country_id: US
      -
        id: MI
        name: Michigan
        country_id: US
      -
        id: MN
        name: Minnesota
        country_id: US
      -
        id: MS
        name: Mississippi
        country_id: US
      -
        id: MO
        name: Missouri
        country_id: US
      -
        id: MT
        name: Montana
        country_id: US
      -
        id: NE
        name: Nebraska
        country_id: US
      -
        id: NV
        name: Nevada
        country_id: US
      -
        id: NH
        name: New Hampshire
        country_id: US
      -
        id: NJ
        name: New Jersey
        country_id: US
      -
        id: NM
        name: New Mexico
        country_id: US
      -
        id: NY
        name: New York
        country_id: US
      -
        id: NC
        name: North Carolina
        country_id: US
      -
        id: ND
        name: North Dakota
        country_id: US
      -
        id: OH
        name: Ohio
        country_id: US
      -
        id: OK
        name: Oklahoma
        country_id: US
      -
        id: OR
        name: Oregon
        country_id: US
      -
        id: PA
        name: Pennsylvania
        country_id: US
      -
        id: PR
        name: Puerto Rico
        country_id: US
      -
        id: RI
        name: Rhode Island
        country_id: US
      -
        id: SC
        name: South Carolina
        country_id: US
      -
        id: SD
        name: South Dakota
        country_id: US
      -
        id: TN
        name: Tennessee
        country_id: US
      -
        id: TX
        name: Texas
        country_id: US
      -
        id: UT
        name: Utah
        country_id: US
      -
        id: VT
        name: Vermont
        country_id: US
      -
        id: VA
        name: Virginia
        country_id: US
      -
        id: WA
        name: Washington
        country_id: US
      -
        id: WV
        name: West Virginia
        country_id: US
      -
        id: WI
        name: Wisconsin
        country_id: US
      -
        id: WY
        name: Wyoming
        country_id: US

We could then make use of this in our app with a simple data model like this:

e.g. app/models/data/country.rb

Data::Country = Data.define(:id, :name, :states) do
  include ConfigFor::DataModel
  config :countries
end

We could then access our data like:

Data::Country.find('AU')
# =>
# #<data Data::Country
#  id="AU",
#  name="Australia",
#  states=
#   [{id: "ACT", name: "Australian Capital Territory", country_id: "AU"},
#    {id: "NSW", name: "New South Wales", country_id: "AU"}, ...

Data::Country.find_by(name: 'United States')
# =>
# #<data Data::Country
#  id="US",
#  name="United States",
#  states=
#   [{id: "AL", name: "Alabama", country_id: "US"},
#    {id: "AK", name: "Alaska", country_id: "US"}, ...

If we want more from the attribute members of our DataModel, we can define cast_#{member} methods.

e.g.

Data::State = Data.define(:id, :name, :country_id)
Data::Country = Data.define(:id, :name, :states) do
  include ConfigFor::DataModel
  config :countries

  private

  def cast_states(data = nil)
    Array(data).map { Data::State[**it] }
  end
end

Now, our data looks like this:

Data::Country.find('AU')
# =>
# #<data Data::Country
#  id="AU",
#  name="Australia",
#  states=
#   [#<data Data::State id="ACT", name="Australian Capital Territory", country_id="AU">,
#    #<data Data::State id="NSW", name="New South Wales", country_id="AU">, ...

But what if we want to query State data directly?

Do we need to duplicate and restructure our data into a new YAML file? Actually, No!

In addition to a filename, the config class method also accepts a transform proc

e.g.

Data::State = Data.define(:id, :name, :country_id) do
  include ConfigFor::DataModel
  config :countries, -> { it.pluck(:states).flatten }
end

Now we can query States directly.

e.g.

Data::State.where(country_id: 'AU')
# =>
# [#<data Data::State id="ACT", name="Australian Capital Territory", country_id="AU">,
#  #<data Data::State id="NSW", name="New South Wales", country_id="AU">,
#  #<data Data::State id="NT", name="Northern Territory", country_id="AU">,
#  #<data Data::State id="QLD", name="Queensland", country_id="AU">,
#  #<data Data::State id="SA", name="South Australia", country_id="AU">,
#  #<data Data::State id="TAS", name="Tasmania", country_id="AU">,
#  #<data Data::State id="VIC", name="Victoria", country_id="AU">,
#  #<data Data::State id="WA", name="Western Australia", country_id="AU">]

Data::Country.find('US').states == Data::State.where(country_id: 'US')
# => true

Data::State.find_by(name: 'Missouri', country_id: 'US')
# => #<data Data::State id="MO", name="Missouri", country_id="US">

_.in? Data::Country.find('US').states
# => true

Primary Keys

Important

If your data model does not have an id member, you need to provide an alternative primary_key

e.g.

Data::Book = Data.define(:name, :author, :isbn) do
  include ConfigFor::DataModel
  config :books

  self.primary_key = :isbn
end

Installation

Add this line to your application's Gemfile:

gem "config_for-data_model"

And then execute:

$ bundle

Or install it yourself as:

$ gem install config_for-data_model

Contributing

Contribution directions go here.

License

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