The simplest gem you'll ever use

Transcript

1. The simplest gem you’ll ever
   use
   @arnvald, 2016
   

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2. The simplest (shortest) gems
   • activesupport-json_encoder (~200 LOC)
   • rails-patch-json-encode (~35 LOC)
   • oj_mimic_json (10 LOC - without comments would
   fit into a tweet)
   

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3. So I wrote a gem
   • gem ‘simple_operation’
   • version 0.1.2 - 33 LOC
   • version 1.0.0 - 42 LOC (2 new features!)
   • ok, ok, it’s not the simplest gem ever (but close!)
   

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4. Services / Actions /
   Operations
   • operation class is a class that performs a set of steps
   • it has input (parameters) and output (result)
   • it has one public method
   • its name is a verb
   • it does not keep any state
   

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5. Example - validate records
   class SelectValidRecords < SimpleOperation.new(:records)
   def call
   records.select {|r| valid?(r) }
   end
   private def valid?(record); …; end
   end
   ValidateRecords.([invalid, invalid2, valid])
   # => [valid]
   

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6. Example - validate records
   class ValidateRecords < SimpleOperation.new(:records)
   result :valid_records, :invalid_records
   def call
   split_records = records.group_by {|r| valid?(r)}
   result split_records[true], split_records[false]
   end
   private def valid?(record); …; end
   end
   ValidateRecords.([invalid, invalid2, valid])
   # => invalid_records=[invalid,invalid2]>
   

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7. Let’s see the code
   

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8. Ruby “tricks” used
   • overriding Class.new
   • using class_eval
   • using class name as a method name (in extension)
   • assigning class to a constant
   • using sugar syntax for call method
   

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9. Resources
   • http://trailblazer.to/gems/operation/
   • https://github.com/arnvald/simple_operation
   

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10. We’re hiring!
    http://bit.do/kaligo-dev
    

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11. Questions?
    

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12. The simplest gem you’ll ever
    use
    @arnvald, 2016
    

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