hydra-validations

Custom validators based on ActiveModel::Validations, developed for Hydra applications.

Dependencies

Ruby >= 1.9.3
ActiveModel 4.x

ActiveFedora 7.x is a run-time dependency of the UniquenessValidator only, and is not provided by this gem.

Installation

Include in your Gemfile:

gem 'hydra-validations'

and

bundle install

Why?

Metadata values are (often) arrays (XML or RDF).
ActiveModel validators don't distinguish between array values and scalar values.
We want validators that validate each member of an array value.

Example: PORO with ActiveModel::Validations

class Validatable
  include ActiveModel::Validations
  attr_accessor :type
  validates_inclusion_of :type, in: %w(text image audio video)
end

>> record = Validatable.new
>> record.type = "text"
>> record.valid?
=> true

>> record.type = ["text", "image"]
>> record.valid?
=> false # not what we want :(

# now let's add Hydra::Validations ...

class CorrectlyValidatable
  include ActiveModel::Validations
  include Hydra::Validations
  attr_accessor :type
  validates_inclusion_of :type, in: %w(text image audio video)
end

>> record = CorrectlyValidatable.new
>> record.type = ["text", "image"]
>> record.valid?
=> true # Yay!

>> record.type = ["text", "newspaper"]
>> record.valid?
=> false

# tailors error message to specific invalid array value
>> puts record.errors.full_messages
Type value "newspaper" is not included in the list

Example: ActiveTriples::Resource

class MyResource < ActiveTriples::Resource
  # ActiveTriples::Resource includes ActiveModel::Validations
  property :type, predicate: RDF::DC.type
  validates_inclusion_of :type, in: %w(text image audio video)
end

>> resource = MyResource.new
>> resource.type = "text"
>> resource.valid?
=> false # Huh? Oh yeah, resource.type is actually an array ...
>> resource.type
=> ["text"]

class YourResource < ActiveTriples::Resource
  include Hydra::Validations
  property :type, predicate: RDF::DC.type
  validates_inclusion_of :type, in: %w(text image audio video)
end

>> resource = YourResource.new
>> resource.type = "text"
=> "text"
>> resource.valid?
=> true # Yay!

>> resource.type << "newspapers"
>> resource.type
=> ["text", "newspapers"]
>> resource.valid?
=> false
>> puts resource.errors.full_messages
Type value "newspapers" is not included in the list

EnumerableBehavior Mixin

Hydra::Validations::EnumerableBehavior is a mixin for an ActiveModel::EachValidator that validates each member of an enumerable value. See the FormatValidator and InclusionValidator below for examples.

EnumerableBehavior overrides validate_each(record, attribute, value) calling super(record, attribute, member) for each member of an enumerable value (i.e., responds to :each). The module "fixes" any error messages to include the specific member that failed validation -- for example, "is invalid" becomes "value \"foo1\" is invalid", so the full message "Identifier is invalid" becomes "Identifer value \"foo1\" is invalid".

allow_nil, allow_blank, and allow_empty

With EnumerableBehavior, validation of non-enumerables is unchanged (validate_each simply returns super); however, the validator options allow_nil and allow_blank apply only to the original value (the enumerable) and not to its members. For example, the value [""] with the option allow_blank: true will not bypass validation. As a result, empty enumerables will fail validation unless allow_blank is true or the special enumerable option allow_empty is true (that option does not bypass validation for non-enumerables that respond to :empty?, e.g., empty strings).

Validators

See also the source code and spec tests.

FormatValidator

Extends ActiveModel::Validations::FormatValidator, adding EnumerableBehavior.

See ActiveModel::Validations::FormatValidator for usage and options.

class FormatValidatable
  include ActiveModel::Validations # required if not already included in class
  include Hydra::Validations
  attr_accessor :field
  validates :field, format: { with: /\A[[:alpha:]]+\Z/ }
  # ... or
  # validates_format_of :field, with: /\A[[:alpha:]]+\Z/
end

>> record = FormatValidatable.new
=> #<FormatValidatable:0x007fe3cc0ece70>
>> record.field = "foo"
=> "foo"
>> record.valid?
=> true
>> record.field = ["foo"]
=> ["foo"]
>> record.valid?
=> true
>> record.field = ["foo", "bar"]
=> ["foo", "bar"]
>> record.valid?
=> true
>> record.field = ["foo1", "bar2"]
=> ["foo1", "bar2"]
>> record.valid?
=> false
>> puts record.errors.full_messages
Field value "foo1" is invalid
Field value "bar2" is invalid

InclusionValidator

Extends ActiveModel::Validations::InclusionValidator, adding EnumerableBehavior.

See ActiveModel::Validations::InclusionValidator for usage and options.

class InclusionValidatable
  include ActiveModel::Validations # required if not already included in class
  include Hydra::Validations
  attr_accessor :field
  validates :field, inclusion: { in: ["foo", "bar", "baz"] }
  # or using helper method ...
  # validates_inclusion_of :field, in: ["foo", "bar", "baz"]
end

>> record = InclusionValidatable.new
=> #<InclusionValidatable:0x007fe3cbc40098>
>> record.field = "foo"
=> "foo"
>> record.valid?
=> true
>> record.field = "foo1"
=> "foo1"
>> record.valid?
=> false
>> record.field = ["foo"]
=> ["foo"]
>> record.valid?
=> true
>> record.field = ["foo", "bar"]
=> ["foo", "bar"]
>> record.valid?
=> true
>> record.field = ["foo", "bar1", "baz"]
=> ["foo", "bar1", "baz"]
>> record.valid?
=> false
>> puts record.errors.full_messages
Field value "bar1" is not included in the list

UniquenessValidator

Validates the uniqueness of an attribute based on a Solr index query.

Intended for ActiveFedora 7.x.

class UniquenessValidatable < ActiveFedora::Base
  include Hydra::Validations # ActiveFedora::Base includes ActiveModel::Validations
  has_metadata name: 'descMetadata', type: ActiveFedora::QualifiedDublinCoreDatastream
  has_attributes :title, datastream: 'descMetadata', multiple: false
  # Can use with multi-value attributes, but single cardinality is required.
  has_attributes :source, datastream: 'descMetadata', multiple: true
  validates :source, uniqueness: { solr_name: "source_ssim" }
  # ... or using helper method
  validates_uniqueness_of :title, solr_name: "title_ssi"
end

CardinalityValidator

Validates the cardinality of the attribute value.

CardinalityValidator extends ActiveModel::Validations::LengthValidator and "tokenizes" values with Array.wrap(value). The "cardinality" of the value is therefore the length the array. Accordingly,

nil and empty enumerables have cardinality 0
scalar values (including empty string) have cardinality 1.

CardinalityValidator customizes the :wrong_length, :too_short and :too_long messages of LengthValidator to use language appropriate to cardinality. You can also override these options.

class CardinalityValidatable
  include ActiveModel::Validations # required if not already included in class
  include Hydra::Validations
  attr_accessor :field
  validates :field, cardinality: { is: 1 }
  # or with helper method ...
  # validates_cardinality_of :field, is: 1
  # or, for single cardinality (same as above) ...
  # validates_single_cardinality_of :field
end

>> record = CardinalityValidatable.new
=> #<CardinalityValidatable:0x007fe3cbc632c8>
>> record.field = "foo"
=> "foo"
>> record.valid?
=> true
>> record.field = ["foo"]
=> ["foo"]
>> record.valid?
=> true
>> record.field = ["foo", "bar"]
=> ["foo", "bar"]
>> record.valid?
=> false
>> puts record.errors.full_messages
Field has the wrong cardinality (should have 1 value(s))

dchandekstark/hydra-validations