Parameter whitelisting for Sinatra. Provides validation, defaults, and post-processing.

An object that works with form_for that encapsulates validations and data management, leaving the business logic up to your testable old self.

Make ActiveRecord defer/postpone saving the records you add to an habtm (has_and_belongs_to_many) association until you call model.save, allowing validation in the style of normal attributes.

Validation for Dutch bank account numbers, Citizen Service Numbers (BSN) and Payment reference

A captcha verification approach for Rails apps, directly integrated into ActiveRecord’s validation mechanism and providing helpers for ActionController and ActionView.

It validates request params outside your controller logic in order to get a clean and nice code, and also helping with the documentation of the operations.

A library for setting up model validations, such as in ActiveRecord.

This gem helps to create wizard like interfaces in terminal applications, has support for nesting and value validation

This gem can parse values, validations, documentation, types, groups and conditions of parameters from your puppet modules

BibleReferenceParser can parse scriptures passages, such as 'Gen. 1:15-18, 21' to the individual books, chapters and verses in the passage. It also provides validation for invalid book names, chapters, and verses.

Combine email validation and transformations to produce canonical email addresses.

Europe is a simple library for retrieving EU government data such as VAT information, VAT validation, currency exchange rates and country information.

Used to validate ContentData objects.

RUT/RUN Chilean validator for Rails models

Rails Devs For Data Integrity catches unique key and foreign key violations coming from the MySQLdatabase and converts them into an error on the ActiveRecord object similar to validation errors

ActiveModel validations for domains (including TLDs), ip addresses and email addresses with fully localization support.

Built for Developers. Ideal for MVPs, product ideation and validation.

AddressValidate is a ruby wrapper for integrating with the USPS address validation api.

MiniTest matchers for ActiveModel::Validations

DataValidator has almost active_recorde validation methods.