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Automatically creates validations basing on the database schema.

branch: master


SchemaValidations is an ActiveRecord extension that keeps your model class definitions simpler and more DRY, by automatically defining validations based on the database schema.

Gem Version Build Status Dependency Status


One of the great things about Rails (ActiveRecord, in particular) is that it inspects the database and automatically defines accessors for all your columns, keeping your model class definitions simple and DRY. That's great for simple data columns, but where it falls down is when your table contains constraints.

create_table :users do |t|
  t.string :email, :null => false, :limit => 30
  t.boolean :confirmed, :null => false

In that case :null => false, :limit => 30 and :boolean must be covered on the model level.

class User < ActiveRecord::Base
  validates :email, :presence => true, :length => 30
  validates :confirmed, :presence => true, :inclusion => { :in => [true, false] }

...which isn't the most DRY approach.

SchemaValidations aims to cover that and does boring work for you. It inspect the database and automatically creates validations basing on the schema. After installing it your model is as simple as it can be.

class User < ActiveRecord::Base

Validations are there but they are created by schema_validations under the hood.


Simply add schema_validations to your Gemfile.

gem "schema_validations"

What if I want something special?

SchemaValidations is highly customizable. You can configure behavior globally via SchemaValidations.setup or per-model via SchemaValidations::ActiveRecord::schema_validations, such as:

class User < ActiveRecord::Base
  schema_validations :except => :email
  validates :email, :presence => true, :length => { :in => 5..30 }

See SchemaValidations::Config for the available options.

This seems cool, but I'm worried about too much automagic

You can globally turn off automatic creation in config/initializers/schema_validations.rb:

SchemaValidations.setup do |config|
  config.auto_create = false

Then in any model where you want automatic validations, just do

class Post < ActiveRecord::Base

You can also pass options as per above.

Which validations are covered?


Constraint Validation
:null => false validates ... :presence => true
:limit => 100 validates ... :length => { :maximum => 100 }
:unique => true validates ... :uniqueness => true

Data types:

Type Validation
:boolean :validates ... :inclusion => { :in => [true, false] }
:float :validates ... :numericality => true
:integer :validates ... :numericality => { :only_integer => true }


SchemaValidations uses the schema_plus gem for its schema queries. That gem will by default auto-create foreign key constraints that you probably want -- but if you don't want them, you can disable them using schema_plus's config.


SchemaValidations supports all combinations of:

  • rails 3.2 or 4.0
  • MRI ruby 1.9.3 or 2.0.0

How do I know what it did?

If you're curious (or dubious) about what validations SchemaValidations defines, you can check the log file. For every assocation that SchemaValidations defines, it generates an info entry such as

[schema_validations] Article.validates_length_of :title, :allow_nil=>true, :maximum=>50

which shows the exact validation definition call.

SchemaValidations defines the validations lazily for each class, only creating them when they are needed (to validate a record of the class, or in response to introspection on the class). So you may need to search through the log file for "schema_validations" to find all the validations, and some classes' validations may not be defined at all if they were never needed for the logged use case.

Release Notes


  • Works with Rails 4.0. Thanks to @davll
  • No longer support Rails < 3.2 or Ruby < 1.9.3



  • New feature: ActiveRecord#validators and ActiveRecord#validators_on now ensure schema_validations are loaded


  • SchemaValidations is derived from the "Red Hill On Rails" plugin schema_validations originally created by harukizaemon (

  • SchemaValidations was created in 2011 by Michał Łomnicki and Ronen Barzel


SchemaValidations is tested using rspec, sqlite3, and rvm, with some hackery to test against multiple versions of rails and ruby. To run the full combo of tests, after you've forked & cloned:

$ cd schema_validations
$ ./runspecs --install  # do this once to install gem dependencies for all versions (slow)
$ ./runspecs # as many times as you like

See ./runspecs --help for other options. You can also pick a specific version of rails and ruby to use, such as: $ rvm use 1.9.2 $ export BUNDLE_GEMFILE=gemfiles/Gemfile.rails-3.1 $ rake spec

If you're running ruby 1.9, code coverage results will be in coverage/index.html -- it should be at 100% coverage.


This gem is released under the MIT license.

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