Created
June 29, 2016 16:21
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| module Result | |
| module Attempt | |
| def self.start(&failable) | |
| Success.new(nil).and_then(&failable) | |
| end | |
| end | |
| end |
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| module Result | |
| class Failure | |
| def initialize(error) | |
| @error = error | |
| end | |
| def and_then | |
| self | |
| end | |
| def finally(success: nil, failure: proc {}) | |
| failure.call(error) | |
| end | |
| private | |
| attr_reader :error | |
| end | |
| end |
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| describe "Result module" do | |
| let(:x) { 1 } | |
| class MyError < StandardError | |
| end | |
| class MyOtherError < StandardError | |
| end | |
| it "is explicitly started and concluded" do | |
| output = Result::Attempt.start { x + 1 }.finally(success: ->(y) { y }) | |
| expect(output).to eq(2) | |
| end | |
| it "chains with #and_then" do | |
| output = Result::Attempt.start { x + 1 }. | |
| and_then { |y| y + 1 }. | |
| and_then { |z| z + 1 }. | |
| finally(success: ->(z) { z }) | |
| expect(output).to eq(4) | |
| end | |
| it "uses Failure class to catch failures" do | |
| output = Result::Attempt.start do | |
| raise MyError | |
| end.finally(failure: ->(e) { e.to_s }) | |
| expect(output).to eq("MyError") | |
| end | |
| it "retains the first error" do | |
| output = Result::Attempt.start do | |
| raise MyError | |
| end. | |
| and_then { raise MyOtherError }. | |
| finally(failure: ->(e) { e.to_s }) | |
| expect(output).to eq("MyError") | |
| end | |
| end |
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| module Result | |
| class Success | |
| def initialize(arg) | |
| @arg = arg | |
| end | |
| def and_then(&failable) | |
| begin | |
| Success.new(failable.call(arg)) | |
| rescue StandardError => e | |
| Failure.new(e) | |
| end | |
| end | |
| def finally(success: proc {}, failure: nil) | |
| success.call(arg) | |
| end | |
| private | |
| attr_reader :arg | |
| end | |
| end |
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