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Reactive record logo
Logo design: Kelly Rauwerdink, @missingdink, Dribbble.

Gem Version

Generates ActiveRecord models to fit a pre-existing Postgres database. Now you can use Rails with the db schema you always wanted. It's your convention over configuration.


  1. Your app is specific to Postgres and proud of it. You use the mature declarative data validation that only a real database can provide.
  2. You have inherited a database or are more comfortable creating one yourself.
  3. You're a grown-ass DBA who doesn't want to speak ORM baby-talk.


  • Fully automatic. It just works.
  • Creates a model for every table.
  • Creates a comprehensive initial migration.
  • Declares key-, uniqueness-, and presence-constraints.
  • Creates associations.
  • Adds custom validation methods for CHECK constraints.


Already familiar with Rails?

  • Set up a postgres db normally
  • Set config.active_record.schema_format = :sql to use a SQL schema.rb
  • After you have migrated up a table, use rails generate reactive_record:install
  • Go examine your generated models

Want more details?

First Include the reactive_record gem in your project's Gemfile. Oh by the way, you'll have to use postgres in your project. Setting up Rails for use with postgres is a bit outside the scope of this document. Please see [Configuring a Database] ( for what you need to do.

gem 'reactive_record'

Bundle to include the library

$ bundle

Next Tell ActiveRecord to go into beast-mode. Edit your config/application.rb, adding this line to use sql as the schema format:

module YourApp
  class Application < Rails::Application
    # other configuration bric-a-brac...
    config.active_record.schema_format = :sql

Next Create the database(s) just like you normally would:

rake db:create

Next Generate a migration that will create the initial table:

$ rails generate migration create_employees

Use your SQL powers to craft some DDL, perhaps the "Hello, World!" of DB applications, employees?

class CreateEmployees < ActiveRecord::Migration
  def up
    execute <<-SQL
      CREATE TABLE employees (
        id         SERIAL,
        name       VARCHAR(255) NOT NULL,
        email      VARCHAR(255) NOT NULL UNIQUE,
        start_date DATE NOT NULL,

        PRIMARY KEY (id),
        CONSTRAINT company_email CHECK (email LIKE '')

  def down
    drop_table :employees

Lastly Deploy the reactive_record generator:

$ rails generate reactive_record:install

Go look at the generated file:

class Employees < ActiveRecord::Base
  set_table_name 'employees'
  set_primary_key :id
  validate :id, :name, :email, :start_date, presence: true
  validate :email, uniqueness: true
  validate { errors.add(:email, "Expected TODO") unless email =~ /.* }

Reactive record does not currently attempt to generate any kind of reasonable error message (I'm working on it) :)



Firstly, thank you, contributors!

Also a special thanks to Joe Nelson, @begriffs, for contributions and inspiration; Reactive Record would not exist without his efforts. Thanks to Bendyworks for the 20% time to work on this project!

And, of course, a huge thank you to Kelly Rauwerdink for her amazing ability to make "an art" even when all I can do is sorta half-articulate what I'm talking about. Thanks!