Everyday Scripting with Ruby 讀書筆記(3)

[size=small]---
利器在手，正則表達式
Our Friend, the Regular Expression
---[/size]

[color=indigo][b]each: 返回初始數組, collect: 收集代碼塊執行值返回新數組..[/b][/color]
irb(main):045:0> [1, 2, 3].each do | ele |
irb(main):046:1* ele * 100
irb(main):047:1> end
=> [1, 2, 3]
irb(main):048:0> [1, 2, 3].collect do | ele |
irb(main):049:1* ele * 100
irb(main):050:1> end
=> [100, 200, 300]

[color=indigo][b]特殊字符+: 匹配字符一次或多次..[/b][/color]
irb(main):054:0> /o+/ =~ "google"
=> 1

[color=indigo][b]特殊字符*: 匹配字符零次或多次..[/b][/color]
irb(main):078:0> /go*gle/ =~ "google"
=> 0

[color=indigo][b]\d: 匹配數字..[/b][/color]
irb(main):055:0> /\d yuan/ =~ "20 yuan"
=> 1

[color=indigo][b]\w: 匹配單詞字符(包括字母, 數字, 下劃線)..[/b][/color]
irb(main):079:0> /\w+/ =~ "google"
=> 0
irb(main):080:0> /\w+/ =~ "12345"
=> 0
irb(main):081:0> /\w+/ =~ "@"
=> nil

[color=indigo][b]match消息: 若存在匹配返回MatchData對象, 它的第零個元素爲第一個匹配的子串..[/b][/color]
irb(main):057:0> match = /\d yuan/.match("I have 20 yuan")
=> #<MatchData:0xdd363ac>
irb(main):058:0> match[0]
=> "0 yuan"
irb(main):059:0> match[1]
=> nil

[color=indigo][b]圓括號: 括住部分爲分組, 通過MatchData對象訪問..[/b][/color]
irb(main):061:0> match = /have (\d+) yuan/.match("I have 20 yuan")
=> #<MatchData:0xdd2af20>
irb(main):062:0> match[0]
=> "have 20 yuan"
irb(main):063:0> match[1]
=> "20"
irb(main):064:0> match[2]
=> nil

[color=indigo][b]sort方法: 默認按升序排列..[/b][/color]
irb(main):067:0> [2, 3, 1].sort
=> [1, 2, 3]
irb(main):068:0> ['dog', 'cat', 'tiger', 'fox'].sort
=> ["cat", "dog", "fox", "tiger"]

[color=indigo][b]太空船操作符<=>: 如果已按正確次序排列返回-1, 否則返回1, 這裏代碼塊進行求反操作以實現降序排列..[/b][/color]
irb(main):069:0> [2, 3, 1].sort do | one, another |
irb(main):070:1* - (one <=> another)
irb(main):071:1> end
=> [3, 2, 1]

# Exercises

def rearrange(england_name)
  has_middlename = /(\w+), (\w+) (\w+)/.match(england_name)
  hasnot_middlename = /(\w+), (\w+)/.match(england_name)

  if(has_middlename)
    lastname = has_middlename[1]
    firstname = has_middlename[2]
    middlename = has_middlename[3]
    "#{firstname} #{middlename[0,1]}. #{lastname}"
  elsif(hasnot_middlename)
    lastname = hasnot_middlename[1]
    firstname = hasnot_middlename[2]
    "#{firstname} #{lastname}" 
  end
end

#---
# Excerpted from "Everyday Scripting in Ruby"
# We make no guarantees that this code is fit for any purpose. 
# Visit http://www.pragmaticprogrammer.com/titles/bmsft for more book information.
#---
require 'test/unit'
require 'myexercise'

class RearrangeTests < Test::Unit::TestCase

  def test_rearrange_with_middle_name
    assert_equal("Dawn E. Marick", rearrange("Marick, Dawn Elaine"))
  end

  def test_rearrange_without_middle_name
    assert_equal("Paul Marick", rearrange("Marick, Paul"))
  end

end

[color=blue][b]** 運行結果 **[/b][/color]
>ruby exercise-4-tests.rb
Loaded suite exercise-4-tests
Started
..
Finished in 0.015 seconds.

2 tests, 2 assertions, 0 failures, 0 errors
>Exit code: 0
[color=blue][b]** **[/b][/color]

# Exercises 另一種寫法

def rearrange(england_name)
  has_or_hasnot_middlename = /(\w+), (\w+)( \w+)?/.match(england_name)

  lastname = has_or_hasnot_middlename[1]
  firstname = has_or_hasnot_middlename[2]

  if(has_or_hasnot_middlename[3])
    middlename = has_or_hasnot_middlename[3]
    middlename_output = middlename[1,1] + '. '  # middlename的首字符是空格
  else
    middlename_output = ''
  end

  "#{firstname} #{middlename_output}#{lastname}"
end