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Flexirest: Validation

You can create validations on your objects just like Rails' built in ActiveModel validations. For example:

class Person < Flexirest::Base
  validates :first_name, presence: true #ensures that the value is present and not blank
  validates :last_name, existence: true #ensures that the value is non-nil only
  validates :password, length: {within:6..12}, message: "Invalid password length, must be 6-12 characters"
  validates :post_code, length: {minimum:6, maximum:8}
  validates :salary, numericality: true, minimum: 20_000, maximum: 50_000
  validates :age, numericality: { minumum: 18, maximum: 65 }
  validates :suffix, inclusion: { in: %w{Dr. Mr. Mrs. Ms.}}

  validates :first_name do |object, name, value|
    object._errors[name] << "must be over 4 chars long" if value.length <= 4
  end

  get :index, '/'
end

Note: the block based validation is responsible for adding errors to object._errors[name] (and this will automatically be ready for << inserting into).

Validations are run when calling valid? or when calling any API on an instance (and then only if it is valid? will the API go on to be called).

full_error_messages returns an array of attributes with their associated error messages, i.e. ["age must be at least 18"]. Custom messages can be specified by passing a :message option to validates. This differs slightly from ActiveRecord in that it's an option to validates itself, not a part of a final hash of other options. This is because the author doesn't like the ActiveRecord format (but will accept pull requests that make both syntaxes valid). To make this clearer, an example may help:

# ActiveRecord
validates :name, presence: { message: "must be given please" }

# Flexirest
validates :name, :presence, message: "must be given please"

Permitting nil values

The default behavior for :length, :numericality and :inclusion validators is to fail when a nil value is encountered. You can prevent nil attribute values from triggering validation errors for attributes that may permit nil by adding the :allow_nil => true option. Adding this option with a true value to :length, :numericality and :inclusion validators will permit nil values and not trigger errors. Some examples are:

class Person < Flexirest::Base
  validates :first_name, presence: true
  validates :middle_name, length: { minimum: 2, maximum: 30 }, allow_nil: true
  validates :last_name, existence: true
  validates :nick_name, length: { minimum: 2, maximum: 30 }
  validates :alias, length: { minimum: 2, maximum: 30 }, allow_nil: false
  validates :password, length: { within: 6..12 }
  validates :post_code, length: { minimum: 6, maximum: 8 }
  validates :salary, numericality: true, minimum: 20_000, maximum: 50_000
  validates :age, numericality: { minimum: 18, maximum: 65 }
  validates :suffix, inclusion: { in: %w{Dr. Mr. Mrs. Ms.}}
  validates :golf_score, numericality: true, allow_nil: true
  validates :retirement_age, numericality: { minimum: 65 }, allow_nil: true
  validates :cars_owned, numericality: true
  validates :houses_owned, numericality: true, allow_nil: false
  validates :favorite_authors, inclusion: { in: ["George S. Klason", "Robert T. Kiyosaki", "Lee Child"] }, allow_nil: true
  validates :favorite_artists, inclusion: { in: ["Claude Monet", "Vincent Van Gogh", "Andy Warhol"] }
  validates :favorite_composers, inclusion: { in: ["Mozart", "Bach", "Pachelbel", "Beethoven"] }, allow_nil: false
end

In the example above, the following results would occur when calling valid? on an instance where all attributes have nil values:

  • :first_name must be present
  • :last_name must be not be nil
  • :nick_name must be not be nil
  • :alias must not be nil
  • :password must not be nil
  • :post_code must not be nil
  • :salary must not be nil
  • :age must not be nil
  • :suffix must not be nil
  • :cars_owned must not be nil
  • :houses_owned must not be nil
  • :favorite_artists must not be nil
  • :favorite_composers must not be nil

The following attributes will pass validation since they explicitly allow_nil:

  • :middle_name
  • :golf_score
  • :retirement_age
  • :favorite_authors

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