正則表達式結尾處的「i」是什麼意思？

Question

%r{\.(gif|jpg|png)$}i 

i在行尾是什麼意思？我知道%r是指正則表達式，但這裏的「我」是什麼？

我試着先在Google上搜索，但是很難找到關於這個小東西的信息。

Answer 1

i修飾符表示正則表達式在匹配文本時會忽略大小寫。你可以閱讀更多關於其他正則修飾符here。

# with i modifier 
%r{.(gif|jpg|png)$}i === ".JpG" #=> true 
%r{.(gif|jpg|png)$}i === ".jpg" #=> true 

# without i modifier 
%r{.(gif|jpg|png)$} === ".JpG" #=> false 
%r{.(gif|jpg|png)$} === ".jpg" #=> true 

注：.在你的正則表達式的意思是「任何單個字符除換行符」，而不是「點字符」。如果您需要匹配點字符，用反斜槓進行轉義：\.

%r{.(gif|jpg|png)$} === "ajpg" # => true 
%r{\.(gif|jpg|png)$} === "ajpg" # => false 
%r{\.(gif|jpg|png)$} === ".jpg" # => true 

Answer 2

Ruby有ri這是您的本地Ruby的文件的副本。

打開終端窗口或控制檯，然後輸入ri Regexp，您將獲得Regexp的文檔。通讀它，你會發現：

 
== Options 

The end delimiter for a regexp can be followed by one or more single-letter 
options which control how the pattern can match. 

* /pat/i - Ignore case 
* /pat/m - Treat a newline as a character matched by . 
* /pat/x - Ignore whitespace and comments in the pattern 
* /pat/o - Perform #{} interpolation only once 

i, m, and x can also be applied on the subexpression level with the 
(?on-off) construct, which enables options on, and disables 
options off for the expression enclosed by the parentheses. 

     /a(?i:b)c/.match('aBc') #=> # 
     /a(?i:b)c/.match('abc') #=> #