问题描述
分解下面的代码以了解我的正则表达式和gsub理解:
Breaking up the below code to understand my regex and gsub understanding:
str = "abc/def/ghi.rb"
str = str.gsub(/^.*\//, '')
#str = ghi.rb
^:字符串的开头
\/:/
^.*\/:从字符串中/开始到最后出现的所有内容
^.*\/ : everything from beginning to the last occurrence of / in the string
我对表达的理解正确吗?
Is my understanding of the expression right?
.*如何正常工作?
推荐答案
您的一般理解是正确的.整个正则表达式将匹配abc/def/，而String#gsub会将其替换为空字符串.
Your general understanding is correct. The entire regex will match abc/def/ and String#gsub will replace it with empty string.
但是，请注意 String#gsub 不会在适当位置更改字符串.这意味着str将在替换后包含原始值("abc/def/ghi.rb").要在适当位置进行更改，可以使用 .
关于
.*的工作方式-正则表达式引擎使用的算法称为回溯.由于.*是贪婪的(将尝试匹配尽可能多的字符)，因此您可以认为会发生以下情况:However, note that String#gsub doesn't change the string in place. This means that str will contain the original value("abc/def/ghi.rb") after the substitution. To change it in place, you can use String#gsub!.
As to how
.* works - the algorithm the regex engine uses is called backtracking. Since .* is greedy (will try to match as many characters as possible), you can think that something like this will happen: 这篇关于如何理解gsub(/^.*\//，'')或正则表达式的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！