如何获取字符串中所有出现模式的索引

Question

string = "Jack and Jill went up the hill to fetch a pail of water. Jack fell down and broke his crown. And Jill came tumbling after. "
d = string.match(/(jack|jill)/i) # -> MatchData "Jill" 1:"Jill"
d.size # -> 1

这仅与看起来第一次出现的情况匹配。

string.scan

完成了部分工作，但它没有告诉任何有关匹配模式的索引的信息。

如何获取模式的所有匹配实例及其索引（位置）的列表？

Answer 1

你可以使用

.scan

和

$`

全局变量，这意味着最后一次成功匹配左边的字符串，但它在平常的

.scan

中不起作用，所以你需要这个hack（偷来的）来自这个答案）：

string = "Jack and Jill went up the hill to fetch a pail of water. Jack fell down and broke his crown. And Jill came tumbling after. "  
string.to_enum(:scan, /(jack|jill)/i).map do |m,|
  p [$`.size, m]
end

输出：

[0, "Jack"]
[9, "Jill"]
[57, "Jack"]
[97, "Jill"]

更新：

注意 Lookbehind 的行为 – 您将获得真正匹配部分的索引，而不是 look 的索引：

irb> "ab".to_enum(:scan, /ab/     ).map{ |m,| [$`.size, $~.begin(0), m] }
=> [[0, 0, "ab"]]
irb> "ab".to_enum(:scan, /(?<=a)b/).map{ |m,| [$`.size, $~.begin(0), m] }
=> [[1, 1, "b"]]

Answer 2

如果您只想将“Jack”的位置放入数组中，这里是对 Nakilon 答案的修改

location_array = Array.new

string = "Jack and Jack went up the hill to fetch a pail of Jack..."  
string.to_enum(:scan,/(jack)/i).map do |m,|
    location_array.push [$`.size]
end