dry-validation

Data validation library based on predicate logic and rule composition.

Overview

Unlike other, well known, validation solutions in Ruby, dry-validation takes a different approach and focuses a lot on explicitness, clarity and preciseness of validation logic. It is designed to work with any data input, whether it's a simple hash, an array or a complex object with deeply nested data.

It is based on an idea that each validation is encapsulated by a simple, stateless predicate, that receives some input and returns either true or false.

Those predicates are encapsulated by rules which can be composed together using predicate logic. This means you can use the common logic operators to build up a validation schema.

Validations can be described with great precision, dry-validation eliminates ambigious concepts like presence validation where we can't really say whether some attribute or key is missing or it's just that the value is nil.

In dry-validation type-safety is a first-class feature, something that's completely missing in other validation libraries, and it's an important and useful feature. It means you can compose a validation that does rely on the type of a given value. In example it makes no sense to validate each element of an array when it turns out to be an empty string.

The DSL

The core of dry-validation is rule composition and predicate logic. The DSL is a simple front-end for that. It only allows you to define the rules by using predicate identifiers. There are no magical options, conditionals and custom validation blocks known from other libraries. The focus is on pure validation logic expressed in a concise way.

The DSL is very abstract, it builds a rule AST which is compiled into an array of rule objects. This means alternative interfaces could be easily build.

When To Use?

Always and everywhere. This is a general-purpose validation library that can be used for many things and it's multiple times faster than ActiveRecord/ActiveModel::Validations and strong-parameters.

Possible use-cases include validation of:

Form params
"GET" params
JSON documents
YAML documents
Application configuration (ie stored in ENV)
Replacement for ActiveRecord/ActiveModel::Validations
Replacement for strong-parameters
etc.

Synopsis

Please refer to the wiki for full usage documentation.

class UserSchema < Dry::Validation::Schema
  key(:name) { |name| name.filled? }
  
  key(:email) { |email| email.filled? & email.format?(EMAIL_REGEX) }
  
  key(:age) { |age| age.none? | age.int? }
  
  key(:address) do |address|
   address.key(:street, &:filled?)
   address.key(:city, &:filled?)
   address.key(:zipcode, &:filled?)
  end
end

Status and Roadmap

This library is in an early stage of development but you are encauraged to try it out and provide feedback.

For planned features check out the issues.

License

See LICENSE file.