reactive_record from Chris Wilson is a nifty library that generates ActiveRecord models to fit a pre-existing PostgreSQL database.

You just use typical DDL to define your PostgreSQL tables, run the reactive_record generator, and voilĂ : it will create a model file for each of your tables, define validations using key/uniqueness/presence constraints, and even set up your associations for you.

Here’s an example employees table from the README:

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 '%@example.com')
      );
    SQL
  end

  def down
    drop_table :employees
  end
end

And the generated model:

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 =~ /.*@example.com/ }
end

Pretty cool. As Chris says, it’s your convention over configuration. Get the gem or check out the source on GitHub.


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