program4_validation.rb

require 'active_model'

class Person
  include ActiveModel::Validations

  attr_accessor :name, :age

  def initialize(name: nil, age: nil)
    @name = name
    @age = age
  end

  validates :name, :age , presence: true
  validates :age, numericality: { greater_than: 0 }
end

puts 'Empty Person'
person = Person.new
p person.valid?
p person.errors.messages

puts ' with name'
person = Person.new name: 'Bruce Willis'
p person.name
p person.valid?
p person.errors.messages

puts 'With age equal 0'
person = Person.new name: 'Bruce Willis', age: 0
p person.age
p person.valid?
p person.errors.messages


puts 'With age greater than 0'
person = Person.new name: 'Bruce Willis', age: 56
p person.name
p person.age
p person.valid?
p person.errors.messages