1. Improving Code Designwith
Automated Checks
AndyWaite
Engineering ManageratFinanceit
financeit.io/careers
1

2. RuboCop
Categories of rules:
» Linting
» Style
» Security
» Naming
» Metrics
@andyw8 2

3. ASimple PullRequest
class Product
...
+
+ def discounted_price
+ price * 0.5
+ end
end
tests are passing
@andyw8 3

4. RuboCopFailures
Offenses:
app/models/product.rb:1:1:
C: Metrics/ClassLength:
Class has too many lines. [101/100]
class Product < ApplicationRecord ...
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@andyw8 4

5. Configuration
# rubocop.yml
Metrics/ClassLength:
Enabled: false
@andyw8 5

6. 6

7. Code Smells
» Large Class
» Long Function
» Long Parameter List
@andyw8 7

8. Possible Refactorings
For a Large Class:
» Extract Class
» Replace Type Code With Subclass
@andyw8 8

9. RuboCopMetrics
» Metrics/ClassLength
» Large Class (default: 100 lines)
» Metrics/MethodLength
» Long Function (default: 10 lines)
» Metrics/ParameterLists (default: 5 params)
» Long Parameter List
@andyw8 9

10. RuboCopSays...
"Hmm, this class is getting quite large. I wonder if
we should refactor it?"
@andyw8 10

11. AutomatingtheWorkflow
» Aim is to run RuboCop against each pull request
» Tools: Code Climate, HoundCI, Pronto
» Review the warnings
» Choose to act or ignore
@andyw8 11

12. Summary
» Code Metrics can give valuable insights
» Make them part of your automated checks
» Use them to detect potential Code Smells
» Don't make changes only to satisfy RuboCop
» But refactor when it makes sense to you
» Continually evolve your application's design
@andyw8 12

13. Thanks
GitHub/Twitter: @andyw8
awaite@financeit.io
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