dry_monads_pm.rb

require 'dry/monads'
require 'dry/monads/right_biased'
require 'dry/monads/result'
require 'dry/monads/maybe'

module Dry
  module Monads
    module RightBiased
      module Right
        def deconstruct
          [value!]
        end
      end

      module Left
        def deconstruct
          [failure]
        end
      end
    end
  end
end


class Test
  include Dry::Monads::Result::Mixin
  include Dry::Monads::Maybe::Mixin

  def call
    matcher_method(Success([1, 2]))
    matcher_method(Success([0, 3]))
    matcher_method(Success(1))
    matcher_method(Success('test'))
    matcher_method(Failure(:not_found))
    matcher_method(Failure(:other_error))
    matcher_method(Maybe(1))
    matcher_method(Maybe('1'))
    matcher_method(Maybe(nil))
  end

  def matcher_method(monad)
    case monad
    in Success(0, x) then puts "X: #{x.inspect} in Success monad"
    in Success(x: String) then puts "String #{x.inspect} in Success monad"
    in Success(x) then puts "#{x.inspect} in Success monad"
    in Some(x: Integer) then puts "Integer in Some monad"
    in Some(x) then puts "#{x.inspect} in Some monad"
    in None then puts "None in Maybe monad"
    in Failure(:not_found) then puts "NOT FOUND in Failure monad"
    in Failure(x) then puts "#{x.inspect} in Failure monad"
    end
  end
end

Test.new.call

# OUTPUT

# [1, 2] in Success monad
# [0, 3] in Success monad
# 1 in Success monad
# "test" in Success monad
# NOT FOUND in Failure monad
# :other_error in Failure monad
# 1 in Some monad
# "1" in Some monad
# None in Maybe monad