ruby – 如何获取字符串中所有出现的模式的索引

发布时间：2020-12-16 21:51:44 所属栏目：百科来源：网络整理

导读：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 这只是第一次出现的情况. string

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

这只是第一次出现的情况.
string.scan可以部分地完成这项工作,但它并没有告诉任何关于匹配模式的索引.

我如何获取模式的所有匹配实例及其索引(位置)的列表？

解决方法

您可以使用.scan和$`全局变量,这意味着最后一次成功匹配的左侧的字符串,但在通常的.scan中不起作用,所以您需要这个hack(从 this answer偷来)：

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"]

UPD：

注意lookbehind的行为 – 你得到真正匹配的部分的索引,而不是外观：

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

（编辑：李大同）

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