Focus on the replacement operation in the regexp package

In the Go language, the regexp package provides support for regular expressions. Regular expression is a tool for describing string patterns by defining a series of rules to match and manipulate strings. In this article, we will focus on the replacement operation in the regexp package.

The replacement operation in the regexp package mainly uses the two functions ReplaceAllString and ReplaceAllFunc. They can all replace the specified string and return the new string after replacement.

The following is the basic syntax of the ReplaceAllString function:

func ReplaceAllString(src, pattern, replace string) string

Among them, src represents the string to be replaced, pattern is the regular expression for search, and replace is the string to be replaced. The example is as follows:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    src := "Hello, world! Today is 2021-06-30."
    pattern := `\d{4}-\d{2}-\d{2}`
    replace := "tomorrow"
    
    newStr := regexp.MustCompile(pattern).ReplaceAllString(src, replace)
    fmt.Println(newStr)
}

The running result is:

Hello, world! Today is tomorrow.

In the above example, we used \d{4}-\d{2}-\d{2}As a regular expression for search, this regular expression represents a string matching the date format, such as 2021-06-30. Call the ReplaceAllString function to replace the part that matches the regular expression with "tomorrow".

In addition to the ReplaceAllString function, there is also a more powerful function ReplaceAllFunc, which can use a function as a replacement value. This function can generate a replaced string based on the matched content. The following is the basic syntax of the ReplaceAllFunc function:

func ReplaceAllFunc(src string, re *Regexp, repl func([]byte) []byte) string

Among them, src represents the string to be replaced, re is a compiled regular expression, and repl is a function used to generate the replacement string. This function receives a []byte type parameter, which represents the matched content, and returns a []byte type result, which represents the replaced content.

The following is a sample code that shows the function of using ReplaceAllFunc to implement replacement:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    src := "Hello, world! Today is 2021-06-30."
    pattern := `\d{4}-\d{2}-\d{2}`
    
    newStr := regexp.MustCompile(pattern).ReplaceAllFunc([]byte(src), func(matched []byte) []byte {
        // 匹配到的内容为matched
        return []byte("tomorrow")
    })
    
    fmt.Println(string(newStr))
}

The running result is also:

Hello, world! Today is tomorrow.

In the above code, we will match the content It is passed to the repl function as a function parameter, and the return value is used as the replacement result. Here our function directly returns the fixed string "tomorrow".

When replacing, sometimes you need some advanced functions, such as retaining the original case when replacing, extracting the substring contained in the matching result when replacing, etc. The regexp package provides related functions and structures to flexibly implement different replacement requirements.

In short, the regexp package provides us with powerful regular expression support, in which replacement operations are one of the most commonly used functions. Through the introduction of this article, I believe that readers have mastered the basic methods of replacement operations in the regexp package, and can use them flexibly according to actual needs.

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