Veto

Veto provides lightweight validation for plain old ruby objects, using a familiar DSL.

Tested on the following Rubies: MRI 2.0.0, 1.9.3

Installation

Add this line to your application's Gemfile:

gem 'veto'

And then execute:

$ bundle

Or install it yourself as:

$ gem install veto

Usage

# Create a validator
class PersonValidator
    include Veto.validator

    validates :name, :presence => true
    validates :age, :inclusion => 0..100
end

# Create an entity
class Person
    attr_reader :name, :age, :errors
end

person = Person.new 

# Validate entity

validator = PersonValidator.new
validator.valid?(person) # => false
validator.validate!(person) # => # => Veto::InvalidEntity, ["name is not present", "..."]  
validator.errors.full_messages # => ["first name is not present", "..."]

# If entity has errors attr_accessor, errors will be passed to the entity

person.errors # => nil
validator = PersonValidator.new
validator.valid?(person) # => false
person.errors.full_messages # => ["first name is not present", "..."]

Validation Helpers

Presence

Likely the most used validation helper, the presence helper will check that the specified object attribute is not blank. Object attributes that are nil, or respond to empty? and return true, are considered blank. All other values will be considered present. This means that presence helper is safe to use for boolean attributes, where you need to ensure that the attribute value can be true or false, but not nil.

class PersonValidator
    include Veto.validator

    validates :first_name, :presence => true
end

Not Null

Similar to the presence helper, the not_null helper will strictly check that the specified attribute is not null/nil. Any attribute where nil? returns true is considered null. Other values, including blank strings and empty arrays, are all considered not-null and will pass.

class PersonValidator
    include Veto.validator

    validates :first_name, :not_null => true
end

Format

The format helper ensures that the string value of an attribute matches the specified regular expression. It's useful for ensuring that email addresses, URLs, UPC codes, ISBN codes, and the like, are in a specific format. It can also be used to check that only certain characters are used in the string.

class PersonValidator
    include Veto.validator

    validates :email, :format => /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i

        # OR

    validates :email, :format => { :with => /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i }

end

Inclusion

This helper ensures that an attribute is included in a specified set, or range of values.

class PersonValidator
    include Veto.validator

    validates :role, :inclusion => [:webmaster, :admin, :user]

        # OR

    validates :role, :inclusion => { :in => [:webmaster, :admin, :user] }
end

Integer

This helper checks that the specified attribute can be a valid integer. For example, the values 123 and '123' will both pass, but 123.4 and '123.4' will both fail.

class PersonValidator
    include Veto.validator

    validates :age, :integer => true    
end

Numeric

This helper checks that the specified attribute can be a valid float. For example, the values 123.4 and '123.4' will both pass.

class PersonValidator
    include Veto.validator

    validates :height, :numeric => true    
end

Greater Than

This helper checks that the specified attribute can be a valid float which is greater than a specified value.

class PersonValidator
    include Veto.validator

    validates :age, :greater_than => 12    
end

Greater Than Or Equal To

This helper checks that the specified attribute can be a valid float which is greater than or equal to a specified value.

class PersonValidator
    include Veto.validator

    validates :age, :greater_than_or_equal_to => 12    
end

Less Than

This helper checks that the specified attribute can be a valid float which is less than a specified value.

class PersonValidator
    include Veto.validator

    validates :age, :less_than => 11   
end

Less Than Or Equal To

This helper checks that the specified attribute can be a valid float which is less than or equal to a specified value.

class PersonValidator
    include Veto.validator

    validates :age, :less_than_or_equal_to => 11   
end

Exact Length

This helper checks that an attribute is an exact length in characters.

class BookValidator
    include Veto.validator

    validates :isbn, :exact_length => 17

        # OR

    validates :isbn, :exact_length => { :with => 17 }
end

Max Length

This helper checks that an attribute does not exceed a given maximum character length.

class PersonValidator
    include Veto.validator

    validates :first_name, :max_length => 10

        # OR

    validates :first_name, :max_length => { :with => 10 }
end

Min Length

This helper checks that an attribute is longer than a given minimum character length.

class PersonValidator
    include Veto.validator

    validates :first_name, :min_length => 3

        # OR

    validates :first_name, :min_length => { :with => 3 }
end

Length Range

This helper checks that the length of an attribute falls within a given range, or other object that responds to include?

class PersonValidator
    include Veto.validator

    validates :first_name, :length_range => 3..10

        # OR

    validates :first_name, :length_range => { :in => 3..10 } 
end

Common Validation Options

message

The :message option allows you to specify the error message that will be added to the errors object when validation fails.

class PersonValidator
    include Veto.validator

    validates :first_name, :presence => {:message => "has not been set"}
end

on

The :on options allows you to specify which attribute name a given validation error should be applied to.

class PersonValidator
    include Veto.validator

    validates :first_name, :presence => {:on => :last_name}
end

person = Person.new
validator = PersonValidator.new
validator.validate!(person) # => Veto::InvalidEntity, ["last_name is not present"]

Conditional Validation

You may want a validation to run only when a specified condition is satisfied. To accomplish this, you can pass :if and :unless options to the validators. Passing an :if condition to a validator will ensure that the validation is only run if the condition returns true. Passing an :unless condition to a validator will ensure that the validation is always run unless the condition returns true.

Using a symbol with :if and :unless

Passing a symbol to the :if or :unless option will call the corresponding validator method upon validation.

class PersonValidator
    include Veto.validator

    validates :last_name, :presence => true, :if => :first_name_set?

    def first_name_set?
        entity.first_name
    end
end

Using a proc with :if and :unless

A Proc object passed to an :if or :unless condition will be run during validation. The Proc object will receive the entity being validated as an argument.

class PersonValidator
    include Veto.validator

    validates :last_name, :presence => true, :unless => Proc.new{|person| person.first_name.nil? }
end

Using a string with :if and :unless

A string passed to the :if or :unless option will be evaluated in the context of the entity being validated.

class PersonValidator
    include Veto.validator

    validates :last_name, :presence => true, :unless => "first_name.nil?"
end

Grouping Conditional Validations

To conditionally run a block of validations, nest them inside a with_options method.

class PersonValidator
    include Veto.validator

    with_options :if => :person_is_admin? do
        validates :admin_secret_code. :presence => true
        validates :admin_level, :inclusion => [3,4,5]
    end

    def person_is_admin?
        entity.is_admin
    end
end

Combining Conditional Statements

You can use multiple :if and :unless statements together simultaneously in an array. The condition will pass only if all :if conditionals return true, and no :unless statements return true.

class PersonValidator
    include Veto.validator

    validates :first_name, :presence => true, 
                           :if => [:person_has_name?, Proc.new{|person| person.is_human?}], 
                           :unless => ["nameless?", :skip_name_validation?]
end

Conditional Locations

Conditional statements can be assigned as an options hash to the with_options method, the validates method, or an an options hash for an individual validator in the validates method.

class PersonValidator
    include Veto.validator

    with_options :if => :my_condition_1
        validates :first_name. :presence => true, :min_length => 3, :if => :my_condition_2
        validates :last_name, :presence => {:unless => :my_condition_3}, :min_length => 3
    end
end

Custom Validation

Veto provides a few ways to create your own validators and validation methods, when your needs are too complex for the built-in validation syntax.

Custom Methods

You can use a method to check the current state of the entity, and add custom error messages to the errors object if the entity is invalid. Register these methods using the validate method. Multiple validation methods can be assigned at once, as well as a hash of condition options included as the last method argument.

class PersonValidator
    include Veto.validator

    validate :supervisor_must_have_supervisor_code, :admins_have_last_names

    def supervisor_must_have_supervisor_code
        if entity.is_admin? && entity.employees.size > 0 && supervisor_code.nil?
            errors.add(:supervisor_code, "can't be blank")
        end
    end

    def admins_have_last_names
        if entity.is_admin? && entity.last_name
            errors.add(:last_name, "can't be blank")
        end
    end
end

Custom Attribute Validator

Much like the built-in presence, max_length, and format attribute validators, you can create your own custom validator, and refer to it using the validates method. Custom attribute validators must extend the Veto::AttributeValidator class, implement a validate method which receives 5 arguments: entity, attribute, value, errors, and options.

class PersonValidator
    include Veto.validator

    class EmailValidator < ::Veto::AttributeValidator
        def validate(entity, attribute, value, errors, options={})
            unless value.to_s =~ /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i
                errors.add(attribute, "is not a valid email address")
            end
        end
    end

    validates :electronic_address, :email => true
end

Configuration

Call the Veto configure method to yield the configuration object.

Veto.configure do |c|
    ...
end

Messages

The message configuration object, allows you to change the default error message produced by each attribute validator. The message must be in the form of a lambda or Proc, and may or may not receive an argument. Use the example below for reference when customizing messages.

Veto.configure do |c|
    c.message.set(:exact_length, lambda{|exact| "is not #{exact} characters"})
    c.message.set(:format, lambda{"is not valid"})
    c.message.set(:inclusion, lambda{|set| "is not in set: #{set.inspect}"})
    c.message.set(:integer, lambda{"is not a number"})
    c.message.set(:length_range, lambda{"is too short or too long"})
    c.message.set(:max_length, lambda{|max| "is longer than #{max} characters"})
    c.message.set(:min_length, lambda{|min| "is shorter than #{min} characters"})
    c.message.set(:not_null, lambda{"is not present"})
    c.message.set(:numeric, lambda{"is not a number"})
    c.message.set(:presence, lambda{"is not present"})
end

If you would like to change the default message produced by a specified validator, you can do so using through the configuration object.

Create a new validator by including the Veto validator module in your class.

class PersonValidator
    include Veto.validator
end

Working With Errors

Veto's simple errors object is a subclass of hash, with a few additional methods for inspecting the collection of error messages.

errors.add

Adds a method to the errors object.

errors.add(:first_name, "is not present")

errors.empty?

Returns a boolean value representing if the errors object is empty or not.

errors.empty? # => true
errors.add(:first_name, "is not present")
errors.empty? # => false

errors.count

Returns the number of errors present in the errors object.

errors.count # => 0
errors.add(:first_name, "is not present")
errors.count # => 1

errors.on

Returns a list of error message for a given attribute.

errors.on(:first_name) # => nil
errors.add(:first_name, "is not present")
errors.add(:first_name, "is too short")
errors.on(:first_name) # => ["is not present", "is too short"]

errors.full_messages

Returns a list of full error messages.

errors.add(:first_name, "is not present")
errors.add(:last_name, "is too short")
errors.full_messages # => ["first_name is not present", "last_name is too short"]

Veto Model

If your entities and validators have a strict 1-to-1 relationship (an entity will only ever be validated by a single validator, and a validator will only ever validate a single entity), it might make sense to embed the validator directly inside the entity.

The Veto Model extension does exactly this, associating your entity with a specified validator, and adding 3 additional methods to your entity: valid?, validate!, and errors

class Person
    include Veto.model(PersonValidator)
end

person.new
person.valid? # => false
person.errors.full_messages # => ["first name is not present", "last name is not present"]
person.validate! # => Veto::InvalidEntity, ["first name is not present", "..."]

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request