How to Extract String Matches Enclosed in Curly Braces Using Go's `regexp` Package?

Retrieve String Matches with Regular Expressions in Go

In Go, the regexp package offers the capability to search for matches within strings based on regular expressions. This guide illustrates how to extract an array of matches from a given string that contain specific segments enclosed by curly braces.

Problem:

You have a string containing the following pattern:

{city}, {state} {zip}

Your goal is to obtain an array holding all substrings that appear between the curly braces. Despite using the regexp package, you're encountering difficulties in achieving the desired output.

Solution:

To address this issue, consider the following steps:

1. Eliminate Regex Delimiters: Remove the forward slashes wrapping the regular expression.
2. Use Raw String Literals: Define the regular expression using raw string literals, denoted by backticks ``, which allows you to escape regex metacharacters with a single backslash.
3. Remove Capturing Group: For this case, the capturing group {([^{}]*)} is unnecessary because you only need the strings between the curly braces. Therefore, you can use the simplified pattern {[^}]*}.

To retrieve all matches, use FindAllString:

r := regexp.MustCompile(`{[^{}]*}`)
matches := r.FindAllString("{city}, {state} {zip}", -1)

To capture only the parts between the curly braces, employ FindAllStringSubmatch with a pattern containing capturing parentheses:

r := regexp.MustCompile(`{([^{}]*)}`)
matches := r.FindAllStringSubmatch("{city}, {state} {zip}", -1)
for _, v := range matches {
    fmt.Println(v[1])
}

Regex Breakdown:

• { - Matches a literal open curly brace.
• {[^{}]*} - Captures all characters except for curly braces and stores them in a group.
• ([^{}]*) - Similar to above, but the captured portion is assigned to group 1.
• } - Matches a literal close curly brace.

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