Automatic validation based on your database schema column types and limits. Keep your code DRY by inferring column validations from table properties!

Say you had a table setup like this:

create_table "widgets", :force => true do |t|
  t.integer  "quantity", :limit => 2
  t.decimal  "thickness", :precision => 4, :scale => 4
  t.string   "color", :null => false
end

Then these validations are inferred when you add validates_by_schema to your model:

validates :quantity, numericality: { allow_nil: true,
  greater_than: -32768, less_than: 32768}
validates :thickness, numericality: {allow_nil: true, 
  less_than_or_equal_to: 0.999, greater_than_or_equal_to: -0.999}
validates :color, presence: true, length: {allow_nil: false, maximum: 255}

1. Add it to your Gemfile:

gem "validates_by_schema"

2. Then bundle

3. Call it from your ActiveRecord model:

class Widget < ActiveRecord::Base
  validates_by_schema
end

You can also whitelist or blacklist columns with :only or :except options, respectively:

validates_by_schema only: [:body, :description]

validates_by_schema except: [:name, :title]

Column properties are inferred by your database adapter (like pg, mysql2, sqlite3), and does not depend on migration files or schema.rb. As such, you could use this on projects where the database where Rails is not in control of the database configuration.

This has been tested with mysql, postgresql, and sqlite3. It should work with any other database that has reliable adapter.