Adrift at sea, a GPS device will report your precise latitude and longitude, but if you don't know what those numbers mean, you're just as lost as before. Similarly, there are many tools that offer a wide variety of metrics about your code, but other than making you feel good, what are you supposed to do with this knowledge? Let's answer that question by exploring what the numbers mean, how static code analysis can add value to your development process, and how it can help us chart the unexplored seas of legacy code.

1. YOU CAN’T
MISS WHAT
YOU CAN’T
MEASURE

3. Y’uh can’ git the’uh fruhm he’uh
[You can’t get there from here]

11. RED ➭ GREEN ➭ REFACTOR

13. 1. Denial
2. Anger
3. Bargaining
4. Depression
5. Acceptance

14. 1. Depression
2. Bargaining
3. Anger
4. Acceptance
5. Denial

16. @customers =
Person.find_by_contents(@phrase, :columns =>
['first_name', 'last_name', 'business_name',
'email_address', 'phone1'], :include => { :contacts
=> :customer }, :limit => 50).collect { |person|
person.contacts.collect { |contact|
contact.customer } }.flatten

17. {10:51}[1.9.3]~/project:master ✓ ➭ git blame app/controllers/customers_...
...
cf2ee204 (Kerri Miller 2012-02-18 12:09:22 -0700 36)

19. TEST COVERAGE

20. TEST COVERAGE
C0 — % of lines of code that have been executed
C1 — % of branches that have been followed at least
once
C2 — % of unique paths through the source code that
have been followed

22. LINES OF CODE

23. LINES OF CODE
{20:32}[1.9.3]~/project:master ✓ ➭ rake stats
+----------------------+-------+-------+---------+---------+-----+-------+
| Name | Lines | LOC | Classes | Methods | M/C | LOC/M |
+----------------------+-------+-------+---------+---------+-----+-------+
| Controllers | 2297 | 1566 | 18 | 106 | 5 | 12 |
| Helpers | 177 | 137 | 0 | 18 | 0 | 5 |
| Models | 3948 | 2522 | 35 | 272 | 7 | 7 |
| Libraries | 164 | 92 | 4 | 12 | 3 | 5 |
| Model specs | 2863 | 2143 | 1 | 2 | 2 | 1069 |
| View specs | 5 | 3 | 0 | 0 | 0 | 0 |
| Controller specs | 4283 | 3632 | 0 | 0 | 0 | 0 |
| Helper specs | 152 | 108 | 0 | 0 | 0 | 0 |
| Library specs | 51 | 36 | 0 | 0 | 0 | 0 |
+----------------------+-------+-------+---------+---------+-----+-------+
| Total | 13940 | 10239 | 58 | 410 | 7 | 22 |
+----------------------+-------+-------+---------+---------+-----+-------+
Code LOC: 4317 Test LOC: 5922 Code to Test Ratio: 1:1.4

24. STATIC vs DYNAMIC

25. "Data is easy.
Information is hard."
-Dr Ying Li

26. COMPLEXITY

27. CYCLOMATIC

28. lin·e·ar·li

29. ASSIGNMENTS
BRANCHES
CONDITIONALS

30. FLOG
class Test
def blah
a = eval "1+1" # 1.2 (a=) + 6.0 (eval)
if a == 2 then # 1.2 (if) + 1.2(==) + 0.4 (fixnum)
puts "yay" # 1.2 (puts)
end
end
end # 11.2 total

31. • Extract Method
• Decompose Objects
• Rethink your domain model

32. CHURN

33. app/models/user.rb = 84
app/models/invoice.rb = 88

34. Wonderland Trail
Length:
47.2 miles

35. Wonderland Trail
Length:
47.2 miles

36. app/models/user.rb = 84
app/models/invoice.rb = 88

40. {10:54}[1.9.3]~/project:master ✓ ➭ git blame app/models/subscription.rb
...
c9ce82b4 (Kerri Miller 2012-05-18 10:19:47 -0700

41. {20:32}[1.9.3]~/project:master ✓ ➭ flog -a app/models/subscription.rb
1609.9: flog total
61.9: flog/method average
408.8: Subscription#update app/models/subscription.rb:472
323.2: Subscription#new app/models/subscription.rb:250
252.0: Subscription#reply app/models/subscription.rb:137
230.5: Subscription::send_notifications app/models/subscription.rb:78
33.6: Subscription#none
25.5: Subscription#can_expire? app/models/subscription.rb:155
11.7: Subscription::reject_no_ack app/models/subscription.rb:205
4.8: Subscription#initialize app/models/subscription.rb:64
4.4: Subscription#expire! app/models/subscription.rb:183
3.7: Subscription#unexpire! app/models/subscription.rb:194
3.4: Subscription#reason_text app/models/subscription.rb:172
2.2: Subscription#is_current? app/models/subscription.rb:178
2.0: Subscription#to_s app/models/subscription.rb:71

42. {20:33}[1.9.3]~/project:master ✓ ➭ flog -d app/models/subscription.rb
321.7: flog total
32.2: flog/method average
230.5: Subscription::send_notifications app/models/subscription.rb:78
47.8: branch
31.7: ticket
23.1: assignment
17.9: user
17.6: []
12.2: empty?
9.8: support_queue
8.1: deliver
8.0: class
7.6: email_address
7.0: ==

43. {08:16}[1.9.3]~/project:master ✓ ➭ flog -a app/models/subscription.rb
52.8: Subscription::send_notifications app/models/subscription.rb:80
28.8: Subscription#none
25.5: Subscription#can_expire? app/models/subscription.rb:119
10.2: Subscription::set_mail_options app/models/subscription.rb:221
9.8: Subscription::email_staff app/models/subscription.rb:268
8.5: Subscription::filter_subscriptions app/models/subscription.rb:17
7.9: Subscription::email_reviewers app/models/subscription.rb:258
7.3: Subscription::email_subscribers app/models/subscription.rb:169
6.3: Subscription::subscriber_emails app/models/subscription.rb:204
5.0: Subscription::log_rate_limited app/models/subscription.rb:239
4.8: Subscription#initialize app/models/subscription.rb:65
4.7: Subscription::extract_email_addresses app/models/subscription.rb
4.6: Subscription::filter_rate_limited app/models/subscription.rb:248
4.4: Subscription#expire! app/models/subscription.rb:147
4.0: Subscription::wants_notifications_on_own_posts? app/models/subsc
3.7: Subscription#unexpire! app/models/subscription.rb:158
3.4: Subscription#reason_text app/models/subscription.rb:136
3.2: Subscription::valid_recipient? app/models/subscription.rb:187
2.4: Subscription::ok_to_email? app/models/subscription.rb:183
2.2: Subscription#is_current? app/models/subscription.rb:142
2.0: Subscription#to_s app/models/subscription.rb:73
1.5: Subscription::find_reviewers app/models/subscription.rb:254
1.4: Subscription::mail_subject app/models/subscription.rb:217

44. {08:43}[1.9.3]~/project:master ✓ ➭ flog -a app/models/subscription.rb
27.9: Subscription#none
25.5: Subscription#can_expire? app/models/subscription.rb:78
4.8: Subscription#initialize app/models/subscription.rb:65
4.4: Subscription#expire! app/models/subscription.rb:106
3.7: Subscription#unexpire! app/models/subscription.rb:117
3.4: Subscription#reason_text app/models/subscription.rb:95
2.2: Subscription#is_current? app/models/subscription.rb:101
2.0: Subscription#to_s app/models/subscription.rb:73
{08:43}[1.9.3]~/project:master ✓ ➭ flog -a app/models/subscriber_notifier.rb
136.6: flog total
8.5: flog/method average
54.1: SubscriberNotifier::send_notifications app/models/subscriber_notif
12.0: SubscriberNotifier::email_subscribers app/models/subscriber_notifi
10.2: SubscriberNotifier::set_mail_options app/models/subscriber_notifie
9.8: SubscriberNotifier::email_staff app/models/subscriber_notifier.rb
8.5: SubscriberNotifier::filter_subscriptions app/models/subscriber_not
7.9: SubscriberNotifier::email_reviewers app/models/subscriber_notifier
6.3: SubscriberNotifier::subscriber_emails app/models/subscriber_notifi
5.0: SubscriberNotifier::log_rate_limited app/models/subscriber_notifie
4.7: SubscriberNotifier::extract_email_addresses app/models/subscriber_
4.6: SubscriberNotifier::filter_rate_limited app/models/subscriber_noti
4.0: SubscriberNotifier::wants_notifications_on_own_posts? app/models/s
3.2: SubscriberNotifier::valid_recipient? app/models/subscriber_notifie
2.4: SubscriberNotifier::ok_to_email? app/models/subscriber_notifier.rb

46. > gem install flay

47. BEST PRACTICES & STYLE
rails_best_practices
reek
roodi
pelusa
cane

50. THANKS!
★ @kerrizor
★ glass artist
★ vespa mechanic
★ lighting designer
★ professional poker player
★ Senior Developer @ Amazon,
Contour.com, Blue Box Group