The simplest gem you'll ever use

Transcript

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

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)

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!)

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

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]

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]) # => <struct valid_records=[valid], invalid_records=[invalid,invalid2]>

7. Let’s see the code

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

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

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

11. Questions?

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