Just when you thought you couldn’t refactor any more…

Deck for an upcoming talk…

Transcript

1. Just when you thought you couldn’t refactor any more…
2. What’s in a YouTube URL?
3. The problem parse 'youtube.com/watch?v=Cx6aGMC6MjU' => {type: :video, id: 'Cx6aGMC6MjU'} parse 'not-a-youtube-url' => {type: :unknown} parse 'youtube.com/abc' => {type: :channel, name: 'abc'} Correct Complete Clear Compact
4. Step 1: parsing the type parse 'youtube.com/watch?v=Cx6aGMC6MjU' => {type: :video, id: 'Cx6aGMC6MjU'} parse 'not-a-youtube-url' => {type: :unknown} parse 'youtube.com/abc' => {type: :channel, name: 'abc'}
5. String#start_with?
6. String#start_with?([prefixes]+) → true or false # Introduced in Ruby 1.8.7 # Returns true if str starts with one of the prefixes given. 'hello'.start_with? 'hell' # => true # Returns true if one of the prefixes matches. 'hello'.start_with? 'heaven', 'hell' # => true 'hello'.start_with? 'heaven', 'paradise' # => false
7. Using String#start_with? if text.start_with? 'youtube.com/watch?v=' {type: :video} elsif text.start_with? 'youtube.com/' {type: :channel} else {type: :unknown} end Correct Complete Clear Compact ✖ ✖ ✔ ✖
8. The problem parse 'youtube.com/watch?v=(11 letters, digits, _ or -)' => {type: :video, id: …} parse '(anything else)' => {type: :unknown} parse 'youtube.com/(at least 1 letter, digit, _ or -)' => {type: :channel, name: …}
9. String#match?
10. String#match?(pattern) → true or false # Introduced in Ruby 2.4 # Converts pattern to a Regexp (if it isn’t already one), then returns a true or false indicating whether the regexp is matched without updating $~ and other related variables. 'Ruby'.match? %r{P...} # => false 'Ruby'.match? %r{R...} # => true $~ # => nil
11. Using String#match? if text.match? %r{youtube\.com/watch\?v=[\w-]{11}} {type: :video} elsif text.match? %r{youtube\.com/[\w-]+} {type: :channel} else {type: :unknown} end Correct Complete Clear Compact ✔ ✖ ✔ ✖
12. Regexp#===
13. rxp === str → true or false # Following a regular expression literal with the === operator allows you to compare against a String. # Case Equality — Used in case statements. %r{^[a-z]*$} === 'HELLO' # => false %r{^[A-Z]*$} === 'HELLO' # => true case 'HELLO' when %r{^[a-z]*$} then 'Lower case' when %r{^[A-Z]*$} then 'Upper case' end # =>'Upper case'
14. Using String#match? if text.match? %r{youtube\.com/watch\?v=[\w-]{11}} {type: :video} elsif text.match? %r{youtube\.com/[\w-]+} {type: :channel} else {type: :unknown} end Correct Complete Clear Compact ✔ ✖ ✔ ✖
15. Using Regexp#=== and case statement case text when %r{youtube\.com/watch\?v=[\w-]{11}} {type: :video} when %r{youtube\.com/[\w-]+} {type: :channel} else {type: :unknown} end Correct Complete Clear Compact ✔ ✖ ✔ ✔
16. Step 2: parsing everything else parse 'youtube.com/watch?v=Cx6aGMC6MjU' => {type: :video, id: 'Cx6aGMC6MjU'} parse 'not-a-youtube-url' => {type: :unknown} parse 'youtube.com/abc' => {type: :channel, name: 'abc'}
17. Using Regexp#=== and case statement case text when %r{youtube\.com/watch\?v=[\w-]{11}} {type: :video} when %r{youtube\.com/[\w-]+} {type: :channel} else {type: :unknown} end How can we capture and name these matches?
18. Regexp captures
19. Regexp captures # Introduced in Ruby 1.9 # Parentheses can be used for capturing. Capture groups can be referred to by name when defined with the (?<name>) or (?'name') constructs. %r{\$(?<dollars>\d+)\.(?<cents>\d+)}.match '$3.67' # => #<MatchData "$3.67" dollars:"3" cents:"67"> $~['dollars'] # => "3" $~['cents'] # => "67"
20. Using Regexp captures case text when %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} {type: :video, id: $~['id']} when %r{youtube\.com/(?<name>[\w-]+)} {type: :channel, name: $~['name']} else {type: :unknown} end Correct Complete Clear Compact ✔ ✔ ≈ ✖
21. MatchData#named_captures
22. MatchData#named_captures → hash # Introduced in 2.4 # Returns a Hash using named capture. A key of the hash is a name of the named captures. A value of the hash is a string of last successful capture of corresponding group. %r{\$(?<dollars>\d+)\.(?<cents>\d+)}.match '$3.67' # => #<MatchData "$3.67" dollars:"3" cents:"67"> $~.named_captures # => {"dollars" => "3", "cents"=> "67"}
23. Using MatchData#named_captures case text when %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} $~.named_captures.merge type: :video when %r{youtube\.com/(?<name>[\w-]+)} $~.named_captures.merge type: :channel else {type: :unknown} end Correct Complete Clear Compact ✔ ✔ ≈ ≈
24. Using MatchData#named_captures case text when %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} $~.named_captures.merge type: :video when %r{youtu\.be/(?<id>[\w-]{11})} $~.named_captures.merge type: :video when %r{youtube\.com/(?<name>[\w-]+)} $~.named_captures.merge type: :channel else {type: :unknown} end Correct Complete Clear Compact ✔ ✔ ≈ ≈
25. Using MatchData#named_captures case text when %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} $~.named_captures.merge type: :video when %r{youtu\.be/v/(?<id>[\w-]{11})} $~.named_captures.merge type: :video when %r{youtube\.com/channel/UC(?<id>[\w-]{22})} $~.named_captures.merge type: :channel when %r{youtube\.com/(?<name>[\w-]+)} $~.named_captures.merge type: :channel else {type: :unknown} end Correct Complete Clear Compact ✔ ✔ ≈ ✖
26. Enumerable#find
27. Enumerable#find(ifnone = nil) {|obj| block} → obj or nil # Passes each entry in enum to block. Returns the first for which block is not false. If no object matches, calls ifnone and returns its result when it is specified, or nil otherwise. (1..90).find {|i| i % 5 == 0 and i % 7 == 0} # => 35 (1..10).find {|i| i % 5 == 0 and i % 7 == 0} # => nil (1..10).find(-> {0}) do |i| i % 5 == 0 and i % 7 == 0 end # => 0
28. Using Enumerable#find PATTERNS = { %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} => :video, %r{youtube\.com/(?<name>[\w-]+)} => :channel, } PATTERNS.find do |regex, type| if text.match(regex) …return the Regexp captures and the matched type… end end
29. break statement
30. break statement # Introduced before Ruby 1.8.7 # Use break to leave a block early. break accepts a value that supplies the result of the expression it is "breaking" out of: (1..10).each{|value| break if value.even?} # => nil (1..10).each do |value| break(value * 2) if value.even? end # => 4
31. Using Enumerable#find and break PATTERNS = { %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} => :video, %r{youtube\.com/(?<name>[\w-]+)} => :channel, } PATTERNS.find do |regex, type| if text.match(regex) …return the Regexp captures and the matched type… end end
32. Using Enumerable#find and break PATTERNS = { %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} => :video, %r{youtube\.com/(?<name>[\w-]+)} => :channel, } PATTERNS.find do |regex, type| if text.match(regex) break $~.named_captures.merge(type: type) end end
33. Using Enumerable#find and break PATTERNS = { %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} => :video, %r{youtube\.com/(?<name>[\w-]+)} => :channel, } PATTERNS.find(-> { {type: :unknown} }) do |regex, type| if text.match(regex) break $~.named_captures.merge(type: type) end end
34. Using Enumerable#find and break PATTERNS = { %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} => :video, %r{youtube\.com/(?<name>[\w-]+)} => :channel, } PATTERNS.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match(regex) end Correct Complete Clear Compact ✔ ✔ ✔ ≈
35. Using Enumerable#find and break PATTERNS = { %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} => :video, %r{youtu\.be/(?<id>[\w-]{11})} => :video, %r{youtube\.com/(?<name>[\w-]+)} => :channel, } PATTERNS.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match(regex) end Correct Complete Clear Compact ✔ ✔ ✔ ≈
36. Using Enumerable#find and break PATTERNS = { %r{youtube\.com/watch\?v=(?<id>[\w-]{11})} => :video, %r{youtu\.be/(?<id>[\w-]{11})} => :video, %r{youtube\.com/channel/(?<id>UC[\w-]{22})} => :channel, %r{youtube\.com/(?<name>[\w-]+)} => :channel, } PATTERNS.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match(regex) end Correct Complete Clear Compact ✔ ✔ ≈ ≈
37. Using Enumerable#find and break VIDEO_PATTERNS = [ %r{youtube\.com/watch\?v=(?<id>[\w-]{11})}, %r{youtu\.be/(?<id>[\w-]{11})}] CHANNEL_PATTERNS = [ %r{youtube\.com/channel/(?<id>UC[\w-]{22})}, %r{youtube\.com/(?<name>[\w-]+)}] patterns = …first iterate through video patterns, then channel patterns… patterns.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match(regex) end Correct Complete Clear Compact ✔ ✔ ≈ ≈
38. Enumerator.new
39. Enumerator.new # Creates a new Enumerator object, which can be used as an Enumerable. Iteration is defined by the given block, in which a "yielder" object, given as block parameter, can be used to yield a value by calling the yield method (aliased as <<): fib = Enumerator.new do |y| a = b = 1 loop{ y << a; a, b = b, a + b } end fib.take(10) # => [1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
40. Using Enumerable#find and break VIDEO_PATTERNS = [ %r{youtube\.com/watch\?v=(?<id>[\w-]{11})}, %r{youtu\.be/(?<id>[\w-]{11})}] CHANNEL_PATTERNS = [ %r{youtube\.com/channel/(?<id>UC[\w-]{22})}, %r{youtube\.com/(?<name>[\w-]+)}] patterns = Enumerator.new do |patterns| VIDEO_PATTERNS.each {|re| patterns << [re, :video]} CHANNEL_PATTERNS.each {|re| patterns << [re, :channel]} end patterns.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match(regex) end
41. Using Enumerable#find and break VIDEO_PATTERNS = [%r{youtube\.com/watch\?v=(?<id>[\w-]{11})}, %r{youtu\.be/(?<id>[\w-]{11})}] CHANNEL_PATTERNS = [%r{youtube\.com/channel/(?<id>UC[\w-]{22})}, %r{youtube\.com/(?<name>[\w-]+)}] patterns = Enumerator.new do |patterns| VIDEO_PATTERNS.each {|re| patterns << [re, :video]} CHANNEL_PATTERNS.each {|re| patterns << [re, :channel]} end patterns.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match regex end Correct Complete Clear Compact ✔ ✔ ✔ ✔
42. What’s in a YouTube URL?
43. Using Enumerable#find and break VIDEO_PATTERNS = [%r{youtube\.com/watch\?v=(?<id>[\w-]{11})}, %r{youtu\.be/(?<id>[\w-]{11})}] CHANNEL_PATTERNS = [%r{youtube\.com/channel/(?<id>UC[\w-]{22})}, %r{youtube\.com/(?<name>[\w-]+)}] patterns = Enumerator.new do |patterns| VIDEO_PATTERNS.each {|re| patterns << [re, :video]} CHANNEL_PATTERNS.each {|re| patterns << [re, :channel]} end patterns.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match %r{\A(?:https?://)?(?:www\.)?#{regex}\Z} end Correct Complete Clear Compact ✔ ≈ ✔ ✔
44. Using Enumerable#find and break VIDEO_PATTERNS = [%r{youtube\.com/watch\?v=(?<id>[\w-]{11})}, %r{youtu\.be/(?<id>[\w-]{11})}] PLAYLIST_PATTERNS = [%r{youtube\.com/playlist/?\?list=(?<id>UC[\w-]+)}] CHANNEL_PATTERNS = [%r{youtube\.com/channel/(?<id>UC[\w-]{22})}, %r{youtube\.com/(?<name>[\w-]+)}] patterns = Enumerator.new do |patterns| VIDEO_PATTERNS.each {|re| patterns << [re, :video]} PLAYLIST_PATTERNS.each {|re| patterns << [re, :playlist]} CHANNEL_PATTERNS.each {|re| patterns << [re, :channel]} end patterns.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match %r{\A(?:https?://)?(?:www\.)?#{regex}\Z} end Correct Complete Clear Compact ✔ ✔ ✔ ✔
45. The final result VIDEO_PATTERNS = [%r{youtube\.com/watch\?v=(?<id>[\w-]{11})}, %r{youtu\.be/(?<id>[\w-]{11})}] PLAYLIST_PATTERNS = [%r{youtube\.com/playlist/?\?list=(?<id>UC[\w-]+)}] CHANNEL_PATTERNS = [%r{youtube\.com/channel/(?<id>UC[\w-]{22})}, %r{youtube\.com/(?<name>[\w-]+)}] patterns = Enumerator.new do |patterns| VIDEO_PATTERNS.each {|re| patterns << [re, :video]} PLAYLIST_PATTERNS.each {|re| patterns << [re, :playlist]} CHANNEL_PATTERNS.each {|re| patterns << [re, :channel]} end patterns.find(-> { {type: :unknown} }) do |regex, type| break $~.named_captures.merge(type: type) if text.match %r{\A(?:https?://)?(?:www\.)?#{regex}\Z} end $~ MatchData#named_captures break Enumerable#find String#match Optional captures \A … \Z << Enumerator.new %r Captures \w Quantifiers
46. Thanks!