A simple, idiomatic Ruby implementation of a response monad (Success or Failure) for handling success and failure states inspired by https://github.com/maxveldink/sorbet-result.
This is a very simple implementation kept on purpose to be less than 100 LOC (currently at 60) and with no other dependencies than zeitwerk.
Add this line to your application's Gemfile:
gem 'simple_result'The recommended usage is to use the Success and Failure helpers to create responses. You can also use the scoped classes 'SimpleResult::Success' and 'SimpleResult::Failure' if you want.
require 'simple_result'
class MyObject
include SimpleResult::Helpers
def initialize(value)
@value = value
end
def double
Success(@value * 2)
end
end
object = MyObject.new(5)
result = object.double
result.success? # => true
result.payload # => 10
result = object.double.and_then { |value| value + 1 }
result.success? # => true
result.payload # => 11require 'simple_result'
class MyObject
def initialize(value)
@value = value
end
def double
SimpleResult::Success.new(@value * 2)
end
end
object = MyObject.new(5)
result = object.double
result.success? # => true
result.payload # => 10
result = object.double.and_then { |value| value + 1 }
result.success? # => true
result.payload # => 11require 'simple_result'
include SimpleResult::Helpers
success = Success("Hello, World!")
success.success? # => true
success.payload # => "Hello, World!"
failure = Failure("Something went wrong")
failure.failure? # => true
failure.error # => "Something went wrong"
# Blank responses
Success() # => Success with nil payload
Failure() # => Failure with nil errorSuccess("hello")
.and_then { |value| value.upcase }
.and_then { |value| "#{value}!" }
# => "HELLO!"
# Failure short-circuiting
Failure("error")
.and_then { |value| value.upcase }
.and_then { |value| "#{value}!" }
# => Failure("error")def validate(value)
# validation
Success(value)
end
def transform(value)
transformed_value = value.upcase
Success(transformed_value)
end
def present(value)
presenter = "#{value}!!"
Success(presenter)
end
validate("hello")
.and_then { |value| transform(value) }
.and_then { |value| present(value) }
# => "HELLO!"
# Or since Ruby 3.4 you can also use the implicit `it` block parameter
validate("hello")
.and_then { transform(it) }
.and_then { present(it) }
# or if you prefer to write without paranthesis in a more DSL like style:
validate("hello")
.and_then { transform it }
.and_then { present it }# Handle errors only when they occur
Success("data").on_error { |error| puts "Error: #{error}" }
# => Success("data") - block not called
Failure("oops").on_error { |error| puts "Error: #{error}" }
# => Prints "Error: oops", returns Failure("oops")The fallback will be called only when the result is nil or an error.
Please be carefull when using blank Success and Failure values with payload_or_fallback because Success().payload_or_fallback will always return the fallback value.
# Use payload or fallback
Success("value").payload_or_fallback { "default" }
# => "value"
Success(nil).payload_or_fallback { "default" }
# => "default"
Failure("error").payload_or_fallback { "default" }
# => "default"Run tests:
ruby test/test_simple_result.rbRun RuboCop:
rubocopStart an interactive console:
bin/consoleThe gem is available as open source under the MIT License.