如何在iOS Swift中的单词和下划线之间添加空格

import Foundation

extension String {
    func addSpacesBetweenWordsAndUnderscores() -> String {
        let pattern = "([a-z])([A-Z])|_"
        let regex = try! NSRegularExpression(pattern: pattern, options: [])
        let range = NSRange(location: 0, length: self.count)
        
        return regex.stringByReplacingMatches(in: self, options: [], range: range, withTemplate: "$1 $2")
    }
}

let input = "helloWorld_this_is_a_test"
let output = input.addSpacesBetweenWordsAndUnderscores()
print(output)