正则表达式中的字符串替换

Question

我正在尝试使用正则表达式替换字符串中的文本。我使用相同的模式在 c# 中完成了它，但在 swift 中它没有按需要工作。

这是我的代码：

var pattern = "\d(\()*[x]"

let oldString = "2x + 3 + x2 +2(x)"

let newString = oldString.stringByReplacingOccurrencesOfString(pattern, withString:"*" as String, options:NSStringCompareOptions.RegularExpressionSearch, range:nil)


print(newString)

替换后我想要的是：

"2*x + 3 +x2 + 2*(x)"

我得到的是：

"* + 3 + x2 +*)"

Answer 1

Try this:

(?<=\d)(?=x)|(?<=\d)(?=\()

This pattern matches not any characters in the given string, but zero width positions in between characters.

For example, (?<=\d)(?=x) This matches a position in between a digit and 'x'

(?<= is look behind assertion (?= is look ahead.

(?<=\d)(?=\()    This matches the position between a digit and '('

So the pattern before escaping:

(?<=\d)(?=x)|(?<=\d)(?=\()

Pattern, after escaping the parentheses and '\'

\(?<=\d\)\(?=x\)|\(?<=\d\)\(?=\\(\)

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