config/settings - approach to set default values and collections in a Rails application. Good for storing business logic default values, collections, texts

config_for docs

alternatively you can use gem config

create /config/settings.yml:

production:
  url: http://127.0.0.1:8080
  namespace: my_app_production

development:
  url: http://localhost:3001
  namespace: my_app_development

shared:
  foo:
    bar:
      baz: 1
  languages:
    en: english
    de: german
    fr: french

create /config/programming.yml:

shared:
  languages:
    ruby: Ruby
    python: Python
  seniority_levels:
    junior: Junior
    middle: Middle
    senior: Senior

getting values in the rails console:

Rails.application.config_for(:settings).dig(:languages).to_h.invert.to_a
=> [["english", :en], ["german", :de], ["french", :fr]] 

Rails.application.config_for(:settings).dig(:languages)
=> {:en=>"english", :de=>"german", :fr=>"french"} 

Rails.application.config_for(:settings).dig(:namespace)
=> "my_app_development" 

Rails.application.config_for(:programming).dig(:languages)
=> {:ruby=>"Ruby", :python=>"Python"}

use as select in a form:

<%= form.select :language, Rails.application.config_for(:settings).dig(:languages) %>
=> select from [en, de, fr], save to database [english, german, french]
<%= form.select :language, Rails.application.config_for(:settings).dig(:languages).to_h.invert.to_a %>
=> select from [english, german, french], save to database [en, de, fr]