gem 'simple_validate'

require 'simple_validate'

class Person
  include SimpleValidate
  attr_accessor :name, :age
  
  validates_presence_of :name, :age
  validates_type_of :age, as: :integer
end

=> p = Person.new
=> #<Person:0x007f9431536408>
=> p.valid?
=> false
=> p.errors
=> #<SimpleValidate::Errors:0x007f94318b4df0
 @messages=
  {:age=>["can't be empty", "must be an integer"],
   :name=>["can't be empty"]}>

  validates_presence_of :attribute

  validates_type_of :attribute, as: :string

  validates_format_of :attribute, with: /[A-Z]+/

  validates_length_of :attribute, in: 6..9

  validates_inclusion_of :domain, in: [:net, :com]
  validates_exclusion_of :name, in: [:Bojack, :Horseman]

  validates_presence_of :attribute, message: 'attribute is required!'

  validates_presence_of :attribute, if: Proc.new { true }