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Refactoring. Ruby edition. Anatoli Makarevich @makaroni4

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Who am I?

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Our projects look like

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In next 15 minutes we will • spice up our knowledge about refactoring • look at some common smells • get acquainted with automated code analysis • become ready to refactor

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Refactoring is but NOT writing tests changing code reducing complexity adding new features

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Refactoring != Moving backwards

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To grow fast you need to grow right.

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What refactoring does? Complexity Readability Maintainability Extensibility

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This is scientific! Martin Fowler, 1999

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Your desk books are:

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Code Smell Any symptom in the source code of a program that possibly indicates a deeper problem Kent Beck

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Let’s smell it!

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Code smells Long method Duplications Heavy class Stupid name Too many params Feature envy Ubercallback Complex conditions

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Refactoring cycle Check test coverage Write tests if needed Change code Ensure that tests pass Check overall complexity

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Find code smells Check test coverage Write tests if needed Change code Ensure that tests pass Check overall complexity

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Check test coverage Check test coverage Write tests if needed Change code Ensure that tests pass Check overall complexity

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Write new tests if needed Check test coverage Write tests if needed Change code Ensure that tests pass Check overall complexity

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reFACTOR Check test coverage Write tests if needed Change code Ensure that tests pass Check overall complexity

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Ensure that tests pass Check test coverage Write tests if needed Change code Ensure that tests pass Check overall complexity

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Automate tests! Check test coverage Write tests if needed Change code Ensure that tests pass Check overall complexity Travis CI Jenkins CI Gitlab CI

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Automate complexity analysis? Check test coverage Write tests if needed Change code Ensure that tests pass Check overall complexity

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Could complexity analysis be automated?

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? How can we process code?

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s(:class, :Sexp, s(:const, :Array), s(:defn, :sexp_type, s(:args), s(:call, nil, :first)), s(:defn, :sexp_body, s(:args), s(:call, nil, :[], s(:lit, 1..-1)))) S-expressions

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s(:class, :Sexp, s(:const, :Array), s(:defn, :sexp_type, s(:args), s(:call, nil, :first)), s(:defn, :sexp_body, s(:args), s(:call, nil, :[], s(:lit, 1..-1)))) Sexp operator

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s(:class, :Sexp, s(:const, :Array), s(:defn, :sexp_type, s(:args), s(:call, nil, :first)), s(:defn, :sexp_body, s(:args), s(:call, nil, :[], s(:lit, 1..-1)))) Sexp body

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Automated analysis • Long methods • Complex class • Stupid variable name

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Long method s(:class, :Sexp, s(:const, :Array), s(:defn, :sexp_type, s(:args), s(:call, nil, :first)), s(:defn, :sexp_body, s(:args), s(:call, nil, :[], s(:lit, 1..-1)))) Find method Sexp :defn

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Long method s(:class, :Sexp, s(:const, :Array), s(:defn, :sexp_type, s(:args), s(:call, nil, :first)), s(:defn, :sexp_body, s(:args), s(:call, nil, :[], s(:lit, 1..-1)))) Find method Sexp :defn Count sexp operators

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Complex class s(:class, :Sexp, s(:const, :Array), s(:defn, :sexp_type, s(:args), s(:call, nil, :first)), s(:defn, :sexp_body, s(:args), s(:call, nil, :[], s(:lit, 1..-1)))) Find method Sexp :class

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Complex class s(:class, :Sexp, s(:const, :Array), s(:defn, :sexp_type, s(:args), s(:call, nil, :first)), s(:defn, :sexp_body, s(:args), s(:call, nil, :[], s(:lit, 1..-1)))) Find method Sexp :class Cound weights of Sexp operators

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Stupid variable name s(:class, :HomerSimpson, s(:const, :BlahBlahBlah), s(:defn, :donuts, s(:args), s(:call, nil, :fist)), s(:defn, :beersnstuff, s(:args), s(:call, nil, :[], s(:lit, 1..-1))))

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Automated analysis

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Refactoring != Rehacktoring @katrinyx

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It is about perception We READ code, NOT COMPILE it.

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After this talk do: • gem install flog • gem install flay • gem install reek • flog PROJECT_PATH • flay PROJECT_PATH • reek PROJECT_PATH

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Let’s refactor! Anatoli Makarevich @makaroni4