How to Simulate Named Capturing Groups in Go Regular Expressions?

How to Emulate Capturing Groups in Go Regular Expressions

In contrast to Ruby and Java, which employ PCRE-compatible regular expressions that support capturing groups, Go employs Google's RE2 library, which does not natively provide this functionality. This article explores how to achieve a similar effect in Go.

Consider the following Ruby regular expression with capturing groups:

(?<Year>\d{4})-(?<Month>\d{2})-(?<Day>\d{2})

This pattern matches date strings like "2001-01-20" and captures the year, month, and day values into named groups accessible via their names, such as ["Year"].

To emulate this behavior in Go, the "P" prefix must be added to capture group names:

(?P<Year>\d{4})-(?P<Month>\d{2})-(?P<Day>\d{2})

For example, the following Go code demonstrates how to utilize this modified pattern:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    r := regexp.MustCompile(`(?P<Year>\d{4})-(?P<Month>\d{2})-(?P<Day>\d{2})`)
    fmt.Printf("%#v\n", r.FindStringSubmatch(`2015-05-27`))
    fmt.Printf("%#v\n", r.SubexpNames())
}

The FindStringSubmatch function returns the captured groups, while SubexpNames provides the names of the capturing groups, allowing you to access their values.

By adding the "P" prefix to capture group names and leveraging the SubexpNames function, it is possible to emulate the functionality of capturing groups in Ruby regular expressions when working with Go's RE2 library.

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