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Was chatting with @mfeathers about retaining Ruby's chained Enumerable style, but finding a way to inject names that reflects the application domain (as opposed to just littering functional operations everywhere, which may be seen as a sort of Primitive Obsession)
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| module FunctionalQuery | |
| def initialize(collection) | |
| @collection = collection | |
| end | |
| def result | |
| @collection | |
| end | |
| def average_by_attr(attr) | |
| map {|key, value| [key, Wrapper.new(value).average(attr)] } | |
| end | |
| def average(attr) | |
| map {|el| el[attr]}.reduce(:+).to_f / size | |
| end | |
| def transform_keys | |
| @collection = {}.tap do |transformed| | |
| @collection.each_key do |key| | |
| transformed[yield(key)] = @collection[key] | |
| end | |
| end | |
| self | |
| end | |
| def method_missing(method, *args, &block) | |
| if @collection.respond_to?(method) | |
| response = @collection.send(method, *args, &block) | |
| if response.is_a? Enumerable | |
| @collection = response | |
| self | |
| else | |
| response | |
| end | |
| else | |
| super | |
| end | |
| end | |
| class Wrapper | |
| include FunctionalQuery | |
| end | |
| end |
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| # A little toy file demonstrating how to build chainable | |
| # data transformations that reveal some amount of intent | |
| # through named extracted methods. | |
| # | |
| # Kudos to @mfeathers for giving me the idea to try this | |
| # | |
| # Copyright Test Double, LLC, 2016. All Rights Reserved. | |
| require_relative "marketing_refinements" | |
| require_relative "marketing_query" | |
| require_relative "marketing_transform" | |
| class MarketResearch | |
| # Vanilla / Anonymous / Primitive approach to chaining | |
| def income_by_smoking(data) | |
| Hash[ | |
| data.reject {|p| p[:income] < 10_000 }. | |
| group_by { |p| p[:smoker] }. | |
| map { |(is_smoker, people)| | |
| [ | |
| is_smoker ? :smokers : :non_smokers, | |
| people.map {|p| p[:income]}.reduce(:+).to_f / people.size | |
| ] | |
| } | |
| ] | |
| end | |
| # Refined approach to tacking named domain abstractions onto Array/Hash | |
| using MarketingRefinements | |
| def income_by_smoking_fancy(data) | |
| data.exclude_incomes_under(10_000). | |
| separate_people_by(:smoker). | |
| average_income_by_smoking | |
| end | |
| #Wrap data and use method_missing to delegate to Array/Hash | |
| def income_by_smoking_query(data) | |
| MarketingQuery.new(data).exclude_incomes_under(10_000). | |
| separate_people_by(:smoker). | |
| average_income_by_smoking. | |
| result | |
| end | |
| #Declarative DSL style | |
| def income_by_smoking_transform(data) | |
| MarketingTransform.new(data).exclude_incomes_under(10_000). | |
| separate_people_by(:smoker). | |
| average_income_by_smoking. | |
| result | |
| end | |
| end | |
| DATA = [ | |
| {age: 19, smoker: false, income: 10_000, education: :high_school}, | |
| {age: 49, smoker: true, income: 120_000, education: :bachelors}, | |
| {age: 55, smoker: false, income: 400_000, education: :masters}, | |
| {age: 23, smoker: true, income: 10_000, education: :bachelors}, | |
| {age: 70, smoker: false, income: 70_000, education: :phd }, | |
| {age: 34, smoker: false, income: 90_000, education: :masters}, | |
| {age: 90, smoker: true, income: 0, education: :high_school}, | |
| ] | |
| original_result = MarketResearch.new.income_by_smoking(DATA) | |
| fancy_result = MarketResearch.new.income_by_smoking_fancy(DATA) | |
| query_result = MarketResearch.new.income_by_smoking_query(DATA) | |
| transform_result = MarketResearch.new.income_by_smoking_transform(DATA) | |
| puts <<-MSG | |
| Original result: #{original_result} | |
| Fancy result: #{fancy_result} | |
| Query result: #{query_result} | |
| Transform result: #{transform_result} | |
| MSG |
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| require_relative 'functional_query' | |
| class MarketingQuery | |
| include FunctionalQuery | |
| def exclude_incomes_under(min) | |
| reject {|p| p[:income] < min } | |
| end | |
| def separate_people_by(attribute) | |
| group_by { |p| p[attribute] } | |
| end | |
| def average_income_by_smoking | |
| transform_keys { |is_smoker| | |
| is_smoker ? :smokers : :non_smokers | |
| }.average_by_attr(:income).to_h | |
| end | |
| end |
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| module MarketingRefinements | |
| refine Array do | |
| # Domain-specific | |
| def exclude_incomes_under(min) | |
| reject {|p| p[:income] < min } | |
| end | |
| def separate_people_by(attribute) | |
| group_by { |p| p[attribute] } | |
| end | |
| # General-purpose | |
| def average(attr) | |
| map {|el| el[attr]}.reduce(:+).to_f / size | |
| end | |
| end | |
| refine Hash do | |
| # Domain-specific | |
| def average_income_by_smoking | |
| Hash[ | |
| transform_keys { |is_smoker| | |
| is_smoker ? :smokers : :non_smokers | |
| }.map {|key, people| | |
| [key, people.average(:income)] | |
| } | |
| ] | |
| end | |
| # General-purpose | |
| def transform_keys | |
| {}.tap do |result| | |
| self.each_key do |key| | |
| result[yield(key)] = self[key] | |
| end | |
| end | |
| end | |
| end | |
| end |
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| require_relative 'transformer' | |
| class MarketingTransform | |
| include Transformer | |
| transform :exclude_incomes_under, -> (min) { reject {|p| p[:income] < min } } | |
| transform :separate_people_by, -> (attribute) { group_by { |p| p[attribute] } } | |
| transform :average_income_by_smoking, -> do | |
| transform_keys { |is_smoker| is_smoker ? :smokers : :non_smokers }. | |
| average_by_attr(:income). | |
| to_h | |
| end | |
| end |
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| module Transformer | |
| def initialize(collection) | |
| @collection = collection | |
| end | |
| def self.included(cls) | |
| cls.extend Transforms | |
| end | |
| def result | |
| @collection | |
| end | |
| def average_by_attr(attr) | |
| map {|key, value| [key, Wrapper.new(value).average(attr)] } | |
| end | |
| def average(attr) | |
| map {|el| el[attr]}.reduce(:+).to_f / size | |
| end | |
| def transform_keys | |
| @collection = {}.tap do |transformed| | |
| @collection.each_key do |key| | |
| transformed[yield(key)] = @collection[key] | |
| end | |
| end | |
| self | |
| end | |
| def method_missing(method, *args, &block) | |
| if @collection.respond_to?(method) | |
| response = @collection.send(method, *args, &block) | |
| if response.is_a? Enumerable | |
| @collection = response | |
| self | |
| else | |
| response | |
| end | |
| else | |
| super | |
| end | |
| end | |
| module Transforms | |
| def transform(name, body) | |
| define_method(name) do |*args| | |
| instance_exec(*args, &body) | |
| end | |
| end | |
| end | |
| class Wrapper | |
| include Transformer | |
| end | |
| end |
MarketingTransform: Slight tweak to try declarative style...
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MarketingQuery: Attempt to wrap collection to avoid refinements. Original idea was a first-class collection, but it didn't feel like one by the end.