Rails中的簡單正則表達式問題

Question

好的。這很晚了，我很累。

我想匹配字符串中的字符。具體來說就是'a'的出現。就像「一個半」一樣。

如果我有一個全是小寫的字符串。

"one and a half is always good" # what a dumb example. No idea how I thought of that. 

我呼籲它

"one and a half is always good".titleize #=> "One And A Half Is Always Good" 

titleize這是錯誤的，因爲 '和' 和 'A' 應該是小寫。明顯。

所以，我能做的

"One and a Half Is always Good".titleize.tr('And', 'and') #=> "One and a Half Is always Good" 

我的問題：我該如何使「A」的「一」，也沒有留下「始終」到「永遠」？

Answer 1

該做的：

require 'active_support/all' 
str = "one and a half is always good" #=> "one and a half is always good" 

str.titleize.gsub(%r{\b(A|And|Is)\b}i){ |w| w.downcase } #=> "One and a Half is Always Good" 

或

str.titleize.gsub(%r{\b(A(nd)?|Is)\b}i){ |w| w.downcase } #=> "One and a Half is Always Good" 

把你任的最後兩行的選擇。正則表達式模式可以在其他地方創建並作爲變量傳入，用於維護或代碼清潔。

Answer 2

我喜歡格雷格的雙線（先標題化，然後用正則表達式來表達選定的單詞。）FWIW，這是我在項目中使用的函數。經過良好測試，雖然更詳細。你會注意到，我重寫titleize中的ActiveSupport：

class String 
    # 
    # A better titleize that creates a usable 
    # title according to English grammar rules. 
    # 
    def titleize 
    count = 0 
    result = [] 

    for w in self.downcase.split 
     count += 1 
     if count == 1 
     # Always capitalize the first word. 
     result << w.capitalize 
     else 
     unless ['a','an','and','by','for','in','is','of','not','on','or','over','the','to','under'].include? w 
      result << w.capitalize 
     else 
      result << w 
     end 
     end 
    end 

    return result.join(' ') 
    end 
end