Ruby：使用gsub在String中进行条件替换

Question

Given an input string:

<m>1</m>
<m>2</m>
<m>10</m>
<m>11</m>

I would like to replace all values that are not equal to 1 with 5 .
So the output String should look like:

<m>1</m>
<m>5</m>
<m>5</m>
<m>5</m>

I tried using:

gsub(/(<m>)([^1])(<\/m>)/, '\15\3')

But this will not replace 10 and 11 .

Answer 1

#gsub可以选择一个块，并替换为该块的结果：

subject.gsub(/\d+/) { |m| m == '1' ? m : '5' }

Answer 2

没有正则表达式只是因为它是可能的

"1 2 10 11".split.map{|n| n=='1' ? n : '5'}.join(' ')

Answer 3

result = subject.gsub(/\b(?!1\b)\d+/, '5')

Explanation:

\b    # match at a word boundary (in this case, at the start of a number)
(?!   # assert that it's not possible to match
 1    # 1
 \b   # if followed by a word boundary (= end of the number)
)     # end of lookahead assertion
\d+   # match any (integer) number

Edit:

If you just wish to replace numbers that are surrounded by <m> and </m> then you can use

result = subject.gsub(/<m>(?!1\b)\d+<\/m>/, '<m>5</m>')