LittleBIGRuby

This was my presentation about what video games can teach us about code reading. I gave it at MountainWest RubyConf 2009.

Transcript

2. Code Reading 101
3. TWO THINGS TO KNOW ABOUT ME
4. TWO THINGS TO KNOW ABOUT ME I wrote the TextMate book
5. TWO THINGS TO KNOW ABOUT ME I wrote the TextMate book My name is Jim Weirich
6. JAMES EDWARD GRAY II
7. JAMES EDWARD GRAY II I wrote two books for the Pragmatic Programmers: Best of Ruby Quiz and TextMate: Power Editing for the Mac
8. JAMES EDWARD GRAY II I wrote two books for the Pragmatic Programmers: Best of Ruby Quiz and TextMate: Power Editing for the Mac I’ve contributed documentation and patches for some standard libraries, which I now help to maintain
9. JAMES EDWARD GRAY II I wrote two books for the Pragmatic Programmers: Best of Ruby Quiz and TextMate: Power Editing for the Mac I’ve contributed documentation and patches for some standard libraries, which I now help to maintain I built FasterCSV (now CSV), HighLine (with Greg), Elif, and a few other libraries people don’t use
10. JAMES EDWARD GRAY II I wrote two books for the Pragmatic Programmers: Best of Ruby Quiz and TextMate: Power Editing for the Mac I’ve contributed documentation and patches for some standard libraries, which I now help to maintain I built FasterCSV (now CSV), HighLine (with Greg), Elif, and a few other libraries people don’t use I created the Ruby Quiz and ran it for the first three years
15. HI. I’M JAMES AND I READ CODE.
16. HOW MUCH SHOULD YOU READ?
17. HOW MUCH SHOULD YOU READ? My opinion based on the Dreyfus Model of Skill Acquisition.
18. WHY IS CODE READING IMPORTANT?
19. WHY IS CODE READING IMPORTANT? It can show you common idioms
20. WHY IS CODE READING IMPORTANT? It can show you common idioms It’s good to practice breaking down possibly challenging code, because you will always have to work with other’s code
21. WHY IS CODE READING IMPORTANT? It can show you common idioms It’s good to practice breaking down possibly challenging code, because you will always have to work with other’s code Understanding how something works gives you insight into any limitations it has
22. WHY IS CODE READING IMPORTANT? It can show you common idioms It’s good to practice breaking down possibly challenging code, because you will always have to work with other’s code Understanding how something works gives you insight into any limitations it has Seeing bad code helps you write better code
23. WHY IS CODE READING IMPORTANT? It can show you common idioms It’s good to practice breaking down possibly challenging code, because you will always have to work with other’s code Understanding how something works gives you insight into any limitations it has Seeing bad code helps you write better code Knowledge workers always need more ideas
26. INTRODUCING RESTCLIENT
27. WHAT IS RESTCLIENT?
28. WHAT IS RESTCLIENT? Sinatra’s sister library (sometimes called “reverse Sinatra”)
29. WHAT IS RESTCLIENT? Sinatra’s sister library (sometimes called “reverse Sinatra”) It provides a very clean interface to RESTful web services
30. WHAT IS RESTCLIENT? Sinatra’s sister library (sometimes called “reverse Sinatra”) It provides a very clean interface to RESTful web services Simple well-written code (around 500 lines of clear code for the core functionality)
31. WHAT IS RESTCLIENT? Sinatra’s sister library (sometimes called “reverse Sinatra”) It provides a very clean interface to RESTful web services Simple well-written code (around 500 lines of clear code for the core functionality) Plus a couple of exciting features
32. BASIC GET Reading tweets with Twitter’s API
33. BASIC GET Reading tweets with Twitter’s API require "rubygems" require "rest_client" require "json" ! twitter = RestClient::Resource.new( "http://twitter.com/statuses", :user => "JEG2", :password => "secret" ) ! json = twitter["friends_timeline.json"].get tweets = JSON.parse(json) tweets.each do |tweet| # ... end
34. BASIC GET Reading tweets with Twitter’s API require "rubygems" require "rest_client" require "json" ! twitter = RestClient::Resource.new( "http://twitter.com/statuses", :user => "JEG2", :password => "secret" ) ! json = twitter["friends_timeline.json"].get tweets = JSON.parse(json) tweets.each do |tweet| # ... end
35. BASIC POST Posting a tweet with Twitter’s API
36. BASIC POST Posting a tweet with Twitter’s API require "rubygems" require "rest_client" require "json" ! twitter = RestClient::Resource.new( "http://twitter.com/statuses", :user => "JEG2", :password => "secret" ) ! json = twitter["update.json"].post(:status => "Hello from #mwrc!") tweet = JSON.parse(json) # ...
37. BASIC POST Posting a tweet with Twitter’s API require "rubygems" require "rest_client" require "json" ! twitter = RestClient::Resource.new( "http://twitter.com/statuses", :user => "JEG2", :password => "secret" ) ! json = twitter["update.json"].post(:status => "Hello from #mwrc!") tweet = JSON.parse(json) # ...
38. NETWORKING CODE DONE RIGHT
40. def process_result(res) if res.code =~ /\A2\d{2}\z/ decode res['content-encoding'], res.body if res.body elsif %w(301 302 303).include? res.code url = res.header['Location'] ! if url !~ /^http/ uri = URI.parse(@url) uri.path = "/#{url}".squeeze('/') url = uri.to_s end ! raise Redirect, url elsif res.code == "304" raise NotModified, res elsif res.code == "401" raise Unauthorized, res elsif res.code == "404" raise ResourceNotFound, res else raise RequestFailed, res end end def transmit(uri, req, payload) setup_credentials(req) ! net = net_http_class.new(uri.host, uri.port) net.use_ssl = uri.is_a?(URI::HTTPS) net.verify_mode = OpenSSL::SSL::VERIFY_NONE net.read_timeout = @timeout if @timeout net.open_timeout = @open_timeout if @open_timeout ! display_log request_log ! net.start do |http| res = http.request(req, payload) display_log response_log(res) string = process_result(res) ! if string or @method == :head Response.new(string, res) else nil end end rescue EOFError raise RestClient::ServerBrokeConnection rescue Timeout::Error raise RestClient::RequestTimeout end def decode(content_encoding, body) if content_encoding == 'gzip' and not body.empty? Zlib::GzipReader.new(StringIO.new(body)).read elsif content_encoding == 'deflate' Zlib::Inflate.new.inflate(body) else body end end
41. A RESTFUL SHELL (IN 90 LOC)
42. CURL-ISH REQUESTS Fetching the latest tweet from Twitter’s API
43. CURL-ISH REQUESTS Fetching the latest tweet from Twitter’s API $ restclient \ > get http://twitter.com/statuses/friends_timeline.json?count=1 \ > JEG2 secret [{"text":"Sent out first round of Twitter client betas…", "user":{"name":"Jeremy McAnally","screen_name":"jeremymcanally",…}, …}]
44. RESTFUL IRB Interacting with the Twitter API
45. RESTFUL IRB Interacting with the Twitter API $ restclient http://twitter.com/statuses JEG2 secret >> post "update.json", :status => "The RestClient shell is fun." => "{\"text\":\"The RestClient shell is fun.\",…}" >> get "friends_timeline.json?count=1" => "[{\"text\":\"The RestClient shell is fun.\",…}]"
46. RESTFUL IRB Interacting with the Twitter API $ restclient http://twitter.com/statuses JEG2 secret >> post "update.json", :status => "The RestClient shell is fun." => "{\"text\":\"The RestClient shell is fun.\",…}" >> get "friends_timeline.json?count=1" => "[{\"text\":\"The RestClient shell is fun.\",…}]"
47. RESTFUL IRB Interacting with the Twitter API $ restclient http://twitter.com/statuses JEG2 secret >> post "update.json", :status => "The RestClient shell is fun." => "{\"text\":\"The RestClient shell is fun.\",…}" >> get "friends_timeline.json?count=1" => "[{\"text\":\"The RestClient shell is fun.\",…}]"
48. LOGGING IN RUBY
49. GENERATING RUBY Interactively building a RESTful Ruby script
50. GENERATING RUBY Interactively building a RESTful Ruby script $ RESTCLIENT_LOG=twitter_fun.rb restclient … >> post "update.json", :status => "The RestClient shell is fun." => … >> get "friends_timeline.json?count=1" => …
51. GENERATING RUBY Interactively building a RESTful Ruby script $ RESTCLIENT_LOG=twitter_fun.rb restclient … >> post "update.json", :status => "The RestClient shell is fun." => … >> get "friends_timeline.json?count=1" => …
52. GENERATING RUBY Interactively building a RESTful Ruby script $ RESTCLIENT_LOG=twitter_fun.rb restclient … >> post "update.json", :status => "The RestClient shell is fun." => … >> get "friends_timeline.json?count=1" => … # twitter_fun.rb RestClient.post "http://twitter.com/statuses/update.json", "status=The%20RestClient%20shell%20is%20fun.", :content_type=>"application/x-www-form-urlencoded" # => 200 OK | application/json 379 bytes RestClient.get "http://twitter.com/statuses/friends_timeline.json?count=1" # => 200 OK | application/json 381 bytes
55. FASTERCSV IS THE NEW CSV
56. THE LESS BORING PARTS OF CSV
57. THE LESS BORING PARTS OF CSV Tricky data structures are needed
58. THE LESS BORING PARTS OF CSV Tricky data structures are needed Rows need ordered access for their columns
59. THE LESS BORING PARTS OF CSV Tricky data structures are needed Rows need ordered access for their columns Users also like to work with them by header name
60. THE LESS BORING PARTS OF CSV Tricky data structures are needed Rows need ordered access for their columns Users also like to work with them by header name Column names often repeat
61. THE LESS BORING PARTS OF CSV Tricky data structures are needed Rows need ordered access for their columns Users also like to work with them by header name Column names often repeat Now that we have m17n, CSV parses in the encoding of your data (no transcoding is done on your data)
62. THE ARRAY-HASH- WITH-DUPLICATES DATA THING
63. CSV::ROW The various ways to refer to data
64. CSV::ROW The various ways to refer to data require "csv" # using Ruby 1.9 ! data = <<END_DATA Console,Units Sold 2007,Percent,Units Sold 2008,Percent Wii,"719,141",49.4%,"1,184,651",49.6% XBox 360,"333,084",22.9%,"743,976",31.1% PlayStation 3,"404,900",27.8%,"459,777",19.3% END_DATA ps3 = CSV.parse(data, :headers => true, :header_converters => :symbol)[-1] ! ps3[0] # => "PlayStation 3" ps3[:percent] # => "27.8%" ps3[:percent, 3] # => "19.3%" ps3[:percent, ps3.index(:units_sold_2008)] # => "19.3%"
65. CSV::ROW The various ways to refer to data require "csv" # using Ruby 1.9 ! data = <<END_DATA Console,Units Sold 2007,Percent,Units Sold 2008,Percent Wii,"719,141",49.4%,"1,184,651",49.6% XBox 360,"333,084",22.9%,"743,976",31.1% PlayStation 3,"404,900",27.8%,"459,777",19.3% END_DATA ps3 = CSV.parse(data, :headers => true, :header_converters => :symbol)[-1] ! ps3[0] # => "PlayStation 3" ps3[:percent] # => "27.8%" ps3[:percent, 3] # => "19.3%" ps3[:percent, ps3.index(:units_sold_2008)] # => "19.3%"
66. M17N IN ACTION
68. @io = if data.is_a? String then StringIO.new(data) else data end @encoding = if @io.respond_to? :internal_encoding @io.internal_encoding || @io.external_encoding elsif @io.is_a? StringIO @io.string.encoding end @encoding ||= Encoding.default_internal || Encoding.default_external
69. @io = if data.is_a? String then StringIO.new(data) else data end @encoding = if @io.respond_to? :internal_encoding @io.internal_encoding || @io.external_encoding elsif @io.is_a? StringIO @io.string.encoding end @encoding ||= Encoding.default_internal || Encoding.default_external
70. @io = if data.is_a? String then StringIO.new(data) else data end @encoding = if @io.respond_to? :internal_encoding @io.internal_encoding || @io.external_encoding elsif @io.is_a? StringIO @io.string.encoding end @encoding ||= Encoding.default_internal || Encoding.default_external def encode_re(*chunks) Regexp.new(encode_str(*chunks)) end ! def encode_str(*chunks) chunks.map { |chunk| chunk.encode(@encoding.name) }.join end
71. @io = if data.is_a? String then StringIO.new(data) else data end @encoding = if @io.respond_to? :internal_encoding @io.internal_encoding || @io.external_encoding elsif @io.is_a? StringIO @io.string.encoding end @encoding ||= Encoding.default_internal || Encoding.default_external def encode_re(*chunks) Regexp.new(encode_str(*chunks)) end ! def encode_str(*chunks) chunks.map { |chunk| chunk.encode(@encoding.name) }.join end
72. @io = if data.is_a? String then StringIO.new(data) else data end @encoding = if @io.respond_to? :internal_encoding @io.internal_encoding || @io.external_encoding elsif @io.is_a? StringIO @io.string.encoding end @encoding ||= Encoding.default_internal || Encoding.default_external sample = read_to_char(1024) sample += read_to_char(1) if sample[-1..-1] == encode_str("\r") and not @io.eof? ! if sample =~ encode_re("\r\n?|\n") @row_sep = $& break end def encode_re(*chunks) Regexp.new(encode_str(*chunks)) end ! def encode_str(*chunks) chunks.map { |chunk| chunk.encode(@encoding.name) }.join end
73. @io = if data.is_a? String then StringIO.new(data) else data end @encoding = if @io.respond_to? :internal_encoding @io.internal_encoding || @io.external_encoding elsif @io.is_a? StringIO @io.string.encoding end @encoding ||= Encoding.default_internal || Encoding.default_external sample = read_to_char(1024) sample += read_to_char(1) if sample[-1..-1] == encode_str("\r") and not @io.eof? ! if sample =~ encode_re("\r\n?|\n") @row_sep = $& break end def encode_re(*chunks) Regexp.new(encode_str(*chunks)) end ! def encode_str(*chunks) chunks.map { |chunk| chunk.encode(@encoding.name) }.join end
74. OTHER POINTS OF INTEREST
75. OTHER POINTS OF INTEREST The parser
76. OTHER POINTS OF INTEREST The parser Ruby 1.9’s CSV library uses primarily one ugly regular expression from Master Regular Expressions
77. OTHER POINTS OF INTEREST The parser Ruby 1.9’s CSV library uses primarily one ugly regular expression from Master Regular Expressions The old FasterCSV has switched to a non-regex parser to dodge some regex engine weaknesses
78. OTHER POINTS OF INTEREST The parser Ruby 1.9’s CSV library uses primarily one ugly regular expression from Master Regular Expressions The old FasterCSV has switched to a non-regex parser to dodge some regex engine weaknesses FasterCSV::Table is another interesting data structure that can work in columns or rows
81. BJ, SLAVE, AND TERMINATOR
82. WHY THESE LIBRARIES?
83. WHY THESE LIBRARIES? They teach how to build multiprocessing Unix software
84. WHY THESE LIBRARIES? They teach how to build multiprocessing Unix software Covers Thread and fork(), apart and together
85. WHY THESE LIBRARIES? They teach how to build multiprocessing Unix software Covers Thread and fork(), apart and together Using pipes
86. WHY THESE LIBRARIES? They teach how to build multiprocessing Unix software Covers Thread and fork(), apart and together Using pipes Signal handling
87. WHY THESE LIBRARIES? They teach how to build multiprocessing Unix software Covers Thread and fork(), apart and together Using pipes Signal handling And much more
88. WHY THESE LIBRARIES? They teach how to build multiprocessing Unix software Covers Thread and fork(), apart and together Using pipes Signal handling And much more Robust code written by an expert
89. HOW TO ASK YOUR CHILD TO KILL YOU
91. def terminate options = {}, &block options = { :seconds => Float(options).to_i } unless Hash === options ! seconds = getopt :seconds, options trap = getopt :trap, options, lambda{ eval("raise(::Terminator::Error, '#{ seconds }s')", block) } ! handler = Signal.trap(signal, &trap) ! plot_to_kill pid, :in => seconds, :with => signal ! begin block.call ensure Signal.trap(signal, handler) end end
92. def terminate options = {}, &block options = { :seconds => Float(options).to_i } unless Hash === options ! seconds = getopt :seconds, options trap = getopt :trap, options, lambda{ eval("raise(::Terminator::Error, '#{ seconds }s')", block) } ! handler = Signal.trap(signal, &trap) ! plot_to_kill pid, :in => seconds, :with => signal ! begin block.call ensure Signal.trap(signal, handler) end end
94. def plot_to_kill pid, options = {} seconds = getopt :in, options signal = getopt :with, options process.puts [pid, seconds, signal].join(' ') process.flush end
95. def plot_to_kill pid, options = {} seconds = getopt :in, options signal = getopt :with, options process.puts [pid, seconds, signal].join(' ') process.flush end
96. def plot_to_kill pid, options = {} seconds = getopt :in, options signal = getopt :with, options process.puts [pid, seconds, signal].join(' ') process.flush end fattr :process do process = IO.popen "#{ ruby } #{ program.inspect }", 'w+' at_exit do begin Process.kill -9, process.pid rescue Object end end process.sync = true process end
97. def plot_to_kill pid, options = {} seconds = getopt :in, options signal = getopt :with, options process.puts [pid, seconds, signal].join(' ') process.flush end fattr :process do process = IO.popen "#{ ruby } #{ program.inspect }", 'w+' at_exit do begin Process.kill -9, process.pid rescue Object end end process.sync = true process end
99. fattr :program do code = <<-code while(( line = STDIN.gets )) pid, seconds, signal, *ignored = line.strip.split ! pid = Float(pid).to_i seconds = Float(seconds) signal = Float(signal).to_i rescue String(signal) ! sleep seconds ! begin Process.kill signal, pid rescue Object end end code tmp = Tempfile.new "#{ ppid }-#{ pid }-#{ rand }" tmp.write code tmp.close tmp.path end
100. fattr :program do code = <<-code while(( line = STDIN.gets )) pid, seconds, signal, *ignored = line.strip.split ! pid = Float(pid).to_i seconds = Float(seconds) signal = Float(signal).to_i rescue String(signal) ! sleep seconds ! begin Process.kill signal, pid rescue Object end end code tmp = Tempfile.new "#{ ppid }-#{ pid }-#{ rand }" tmp.write code tmp.close tmp.path end
101. fattr :program do code = <<-code while(( line = STDIN.gets )) pid, seconds, signal, *ignored = line.strip.split ! pid = Float(pid).to_i seconds = Float(seconds) signal = Float(signal).to_i rescue String(signal) ! sleep seconds ! begin Process.kill signal, pid rescue Object end end code tmp = Tempfile.new "#{ ppid }-#{ pid }-#{ rand }" tmp.write code tmp.close tmp.path end
102. fattr :program do code = <<-code while(( line = STDIN.gets )) pid, seconds, signal, *ignored = line.strip.split ! pid = Float(pid).to_i seconds = Float(seconds) signal = Float(signal).to_i rescue String(signal) ! sleep seconds ! begin Process.kill signal, pid rescue Object end end code tmp = Tempfile.new "#{ ppid }-#{ pid }-#{ rand }" tmp.write code tmp.close tmp.path end
103. fattr :program do code = <<-code while(( line = STDIN.gets )) pid, seconds, signal, *ignored = line.strip.split ! pid = Float(pid).to_i seconds = Float(seconds) signal = Float(signal).to_i rescue String(signal) ! sleep seconds ! begin Process.kill signal, pid rescue Object end end code tmp = Tempfile.new "#{ ppid }-#{ pid }-#{ rand }" tmp.write code tmp.close tmp.path end
104. fattr :program do code = <<-code while(( line = STDIN.gets )) pid, seconds, signal, *ignored = line.strip.split ! pid = Float(pid).to_i seconds = Float(seconds) signal = Float(signal).to_i rescue String(signal) ! sleep seconds ! begin Process.kill signal, pid rescue Object end end code tmp = Tempfile.new "#{ ppid }-#{ pid }-#{ rand }" tmp.write code tmp.close tmp.path end
105. fattr :program do code = <<-code while(( line = STDIN.gets )) pid, seconds, signal, *ignored = line.strip.split ! pid = Float(pid).to_i seconds = Float(seconds) signal = Float(signal).to_i rescue String(signal) ! sleep seconds ! begin Process.kill signal, pid rescue Object end end code tmp = Tempfile.new "#{ ppid }-#{ pid }-#{ rand }" tmp.write code tmp.close tmp.path end
106. OTHER POINTS OF INTEREST
107. OTHER POINTS OF INTEREST bj – A robust background priority queue for Rails
108. OTHER POINTS OF INTEREST bj – A robust background priority queue for Rails Noticing changes from the outside world via signals
109. OTHER POINTS OF INTEREST bj – A robust background priority queue for Rails Noticing changes from the outside world via signals Managing and monitoring an external job
110. OTHER POINTS OF INTEREST bj – A robust background priority queue for Rails Noticing changes from the outside world via signals Managing and monitoring an external job slave – Trivial multiprocessing with built-in IPC
111. OTHER POINTS OF INTEREST bj – A robust background priority queue for Rails Noticing changes from the outside world via signals Managing and monitoring an external job slave – Trivial multiprocessing with built-in IPC How to set up a “heartbeat” between processes
112. OTHER POINTS OF INTEREST bj – A robust background priority queue for Rails Noticing changes from the outside world via signals Managing and monitoring an external job slave – Trivial multiprocessing with built-in IPC How to set up a “heartbeat” between processes How to run DRb over Unix domain sockets
115. THE ART OF CODE READING
116. PROCESS TIPS
117. PROCESS TIPS Take a deep breath and relax
118. PROCESS TIPS Take a deep breath and relax Not all code sucks
119. PROCESS TIPS Take a deep breath and relax Not all code sucks Don’t start with Rails
120. PROCESS TIPS Take a deep breath and relax Not all code sucks Don’t start with Rails There’s a ton of great stuff in there
121. PROCESS TIPS Take a deep breath and relax Not all code sucks Don’t start with Rails There’s a ton of great stuff in there But it’s a big and complex beast
122. PROCESS TIPS Take a deep breath and relax Not all code sucks Don’t start with Rails There’s a ton of great stuff in there But it’s a big and complex beast Have a goal
123. GETTING THE CODE
124. GETTING THE CODE gem unpack GEM_NAME
125. GETTING THE CODE gem unpack GEM_NAME Use anonymous VCS access to pull a local copy of the code
126. GETTING THE CODE gem unpack GEM_NAME Use anonymous VCS access to pull a local copy of the code Open it in your standard environment as you would if you were going to edit it
127. FINDING THINGS
128. FINDING THINGS Try the conventions first
129. FINDING THINGS Try the conventions first Executables are probably in the bin/ directory
130. FINDING THINGS Try the conventions first Executables are probably in the bin/ directory Look for MyModule::MyClass in lib/my_module/ my_class.rb
131. FINDING THINGS Try the conventions first Executables are probably in the bin/ directory Look for MyModule::MyClass in lib/my_module/ my_class.rb Look for methods in super classes and mixed in modules
132. FINDING THINGS Try the conventions first Executables are probably in the bin/ directory Look for MyModule::MyClass in lib/my_module/ my_class.rb Look for methods in super classes and mixed in modules But remember Ruby is quite dynamic
133. FINDING THINGS Try the conventions first Executables are probably in the bin/ directory Look for MyModule::MyClass in lib/my_module/ my_class.rb Look for methods in super classes and mixed in modules But remember Ruby is quite dynamic Hunt for some “core extensions”
134. UNDERSTANDING THE CODE
135. UNDERSTANDING THE CODE Start with the tests/specs if there are any
136. UNDERSTANDING THE CODE Start with the tests/specs if there are any Check for an “examples/” directory
137. UNDERSTANDING THE CODE Start with the tests/specs if there are any Check for an “examples/” directory Try to load and play with certain classes in isolation
138. UNDERSTANDING THE CODE Start with the tests/specs if there are any Check for an “examples/” directory Try to load and play with certain classes in isolation irb -r a_class_to_play_with
139. UNDERSTANDING THE CODE Start with the tests/specs if there are any Check for an “examples/” directory Try to load and play with certain classes in isolation irb -r a_class_to_play_with Remember Ruby’s reflection methods, like methods()
140. QUESTIONS? About code or other important topics…