Pattern match example (Ruby 2.7)

pattern_match_example.rb

require 'pry'

class Category
  def initialize(attributes)
    @id, @name = *attributes.values_at(:id, :name)
  end

  def valid?
    errors.empty?
  end

  def errors
    messages = []
    messages << "id is missing" if @id.to_s.empty?
    messages << "name is missing" if @name.to_s.empty?
    messages
  end
end

module CategoryMutator
  def self.create(attributes)
    category = Category.new(attributes)
    category.valid? ? [:ok, category] : [:error, category.errors]
  end
end

def example(category_attributes)
  case CategoryMutator.create(category_attributes)
  in :ok, result
    puts "Created category #{result.inspect}"
  in :error, reason
    puts "Error: #{reason.inspect}"
  end
end

example(id: 1, name: "Category 1") #=> Created category #<Category:0x00007fb7468b3d00 @id=1, @name="Category 1">
example(id: 2, name: "") #=> Error: ["name is missing"]