2011 NOTE: Some links in this presentation are no longer valid. Sorry about that.
As a professional developer, especially one who works in Ruby, you hear about code quality all the time. You learn that testing your code and making it easy to maintain are the path to success. You know about TDD, BDD, TATFT and LMNOP. You learn to cycle from red to green to refactoring. We all do our best to write quality, maintainable, reusable code. We're all human, though; some of us slip, and some of us have had to work hard at preventing code smells. In this talk, I'll talk about how I learned to program, how going pro exposed flaws in my coding style, and how I'm working to improve my code quality, sharing some of my old stinky code, the better, refactored versions, and the lessons I've learned in honing my craft.
12. 10 TEXT:HOME
20 GOSUB 100
30 END
100 ?“YES I JUST GOSUBBED FOR
NO REASON WHATSOEVER”
110 RETURN
Friday, June 12, 2009
13. “It is practicaquot;y impossible to teach
good programming style to students
that have had prior exposure to
BASIC: as potential programmers
they are mentaquot;y mutilated beyond
hope of regeneration.”
– Edsger W. Dijkstra
Friday, June 12, 2009
18. C HAD ENOUGH YET?
PROGRAM UGLY
WRITE(UNIT=*, FMT=*) 'FORTRAN!'
END
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19. “[T]he infantile disorder”, by now
nearly 20 years old, is hopelessly
inadequate for whatever computer
application you have in mind
today: it is now too clumsy, too
risky, and too expensive to use.”
– Edsger W. Dijkstra
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26. Get it done. Put the fire out.
Then forget about it.
Friday, June 12, 2009
27. Short, quick scripts
#!/bin/sh
for year in 1996 1997 1998 1999 2000; do
rm -rf backups/${year}
done
echo quot;Sorry, all backups from the pretend Internet money
era have been purged.quot; | /usr/ucb/Mail -s quot;Your restore
requestquot; boss@example.com
Friday, June 12, 2009
85. Why RCov Helps
• To reach full coverage,
you write more tests.
• As you write more tests,
you fix more problems.
• As you fix more problems,
you write better code!
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86. Things To Look Out For
• RCov isn’t perfect.
• It will sometimes miss code that is
covered.
• It is easy to cheat.
• Just because it’s covered doesn’t mean the
code is awesome.
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87. Reek
gem install reek
http://github.com/kevinrutherford/reek
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88. Finds common smells
in your code.
quot;app/controllers/application_controller.rbquot; -- 3 warnings:
ApplicationController#username_for calls user.username multiple times (Duplication)
ApplicationController#username_for doesn't depend on instance state (Utility Function)
ApplicationController#username_for refers to user more than self (Feature Envy)
quot;app/controllers/groups_controller.rbquot; -- 5 warnings:
GroupsController#show calls params multiple times (Duplication)
GroupsController#show calls params[:page] multiple times (Duplication)
GroupsController#show calls params[:page].to_i multiple times (Duplication)
GroupsController#show has approx 6 statements (Long Method)
GroupsController#show/block/block is nested (Nested Iterators)
quot;app/controllers/sessions_controller.rbquot; -- 2 warnings:
SessionsController#create calls flash multiple times (Duplication)
SessionsController#create has approx 8 statements (Long Method)
quot;app/controllers/user_feeds_controller.rbquot; -- 3 warnings:
UserFeedsController#create calls logger multiple times (Duplication)
UserFeedsController#create has approx 6 statements (Long Method)
UserFeedsController#create has the variable name 'e' (Uncommunicative Name)
quot;app/helpers/application_helper.rbquot; -- 14 warnings:
ApplicationHelper::feed_date_for doesn't depend on instance state (Utility Function)
ApplicationHelper::feed_date_for refers to date more than self (Feature Envy)
ApplicationHelper::feedstitch_group_for doesn't depend on instance state (Utility Function)
ApplicationHelper::feedstitch_group_for refers to user more than self (Feature Envy)
ApplicationHelper::link_to_group_feed has 4 parameters (Long Parameter List)
Friday, June 12, 2009 ApplicationHelper::name_for doesn't depend on instance state (Utility Function)
89. Why Reek Helps
• Reek finds common
anti-patterns.
• Anti-patterns are bad habits
that are worth breaking.
• Fewer bad habits ==
better code!
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90. Things To Look Out For
• Reek also isn’t perfect.
• It false-positives often.
• It can only make suggestions.
• It doesn’t catch all possible code smells.
Friday, June 12, 2009
91. Let’s Talk About
How My Code Smells
Or, The Part Of The Presentation That Is Potentiaquot;y
Very Embarrassing To The Presenter
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92. MVC
Learn it. Know it. Live it.
Friday, June 12, 2009
94. Do As I Say,
Not As I Did
Actual client project, 2007 (I am not making this up):
• One controller
• One method
• ~130 LOC
• Actual comment:
# OPTIMIZE: this is ugly
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96. Why???
• Didn’t understand the domain.
• Not thinking in object-oriented
paradigm.
• Not thinking in MVC.
• Not pairing.
• Lousy tests.
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97. What Really Goes
In A Controller?
• Code you need to respond to a
web request and render the result
• Not business logic
• Not complex operations on
objects
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98. Controller Liposuction
• Everything in its right place.
• When you see yourself doing
business logic, move it to the model!
• When you see yourself defining
view logic, move it to the view/
helper!
Friday, June 12, 2009
100. Finding Big Methods
• Too much stuff happening; too
many concerns
• Too many LOC to comprehend
in a glance
• Logic inside logic
Friday, June 12, 2009
101. def response
if @response.nil?
@final_response = false
current = source
path = source.query.nil? ? source.path : quot;#{source.path}?#{source.query}quot;
until @final_response
Net::HTTP.start(current.host, current.port) do |http|
@response = http.get(path, 'User-Agent' => user_agent)
if @response.header['location']
current = URI.parse(@response.header['location'])
path = current.query.nil? ? current.path : quot;#{current.path}?#{current.query}quot;
else
@final_response = true
end
end
end
end
@response
end
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103. Remember
UNIX?
Small tools doing one
job well ⇒ small
methods doing one
job well
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104. Name Methods To
Communicate Intent
thing.expires_at <
Time.now thing.expired?
user.has_accepted_terms &&
!user.suspended
user.can_sign_in?
Friday, June 12, 2009
105. Don’t Do Too Much
In A Method
• When you see a method getting too
long, break it into smaquot;er methods.
• Hint: look for excessive indentation
and nested ifs.
• Hint: a method shouldn’t come close
to filling your editor window.
Friday, June 12, 2009
106. def self.user_agent
quot;Awesome App Ruby/#{RUBY_VERSION}quot;
end
def self.maximum_redirects
4
end
def initialize(url)
@url = url
end
def endpoint_for(uri)
endpoint = uri.path.sub(/^/?$/, '/')
endpoint += quot;?#{uri.query}quot; unless uri.query.blank?
endpoint
end
def fetch(url, redirects_remaining)
return if redirects_remaining == 0
begin
uri = URI.parse(url)
response = Net::HTTP.start(uri.host, uri.port) do |http|
http.get(endpoint_for(uri), {'User-Agent' => self.class.user_agent})
end
if response.is_a?(Net::HTTPRedirection)
response = fetch(response['location'], redirects_remaining - 1)
end
rescue URI::InvalidURIError
RAILS_DEFAULT_LOGGER.warn quot;Error parsing URL: '#{url}'quot;
end
response
end
def response
@response ||= fetch(@url, self.class.maximum_redirects)
end
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107. Self-Review
• Don’t check it in if the tests fail.
• Use continuous integration to keep
yourself honest. (more on this later)
• Look over all your changes before you
commit.
• If you miss something and you’re using
Git, fix it and git commit --amend
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108. Peer Review
• Pair-program whenever you can. Pair
programming comes with built-in peer
review.
• Do regular code reviews with your peers.
During active development, weekly is
good.
• Listen to criticism. Don’t take it personaquot;y.
No one’s perfect.
Friday, June 12, 2009
109. Quality Takes
Time
By law, straight bourbon
must be aged in new, charred
oak barrels for at least two
years. Anything less yields
just whiskey, not bourbon.
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134. Put it all together and
you will write better code.
Friday, June 12, 2009
135. The End.
This has been “Code Stinkers Anonymous”
by Mark Cornick. Thank you!
http://objectsinmirrors.com/
http://twitter.com/mcornick
Please rate this talk on SpeakerRate!
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Friday, June 12, 2009