NSAttributedString: turn (multiple) #username[userid] mentions into clickable #username links - swift

Question

I am in the process of writing code to display mentions within an NSAttributedString, which need to link out to a user profile. The format of the mentions is #username[userid], which would need to be displayed as simply #username, which is tappable.
I have the code working so far that the username becomes clickable, but I now need to remove the [userid] part, which of course modifies the length of the string so that ranges don't match anymore, etc. Not sure how I can solve this.
import Foundation
import UIKit
let comment = "Hello #kevin[1], #john and #andrew[2]!"
let wholeRange = NSRange(comment.startIndex..<comment.endIndex, in: comment)
let regex = try NSRegularExpression(pattern: #"(#[\w.-#]+)\[(\d+)\]"#)
let attributedString = NSMutableAttributedString(string: comment)
regex.enumerateMatches(in: comment, options: [], range: wholeRange) { match, _, _ in
guard let match = match else {
return
}
let userIdRange = Range(match.range(at: 2), in: comment)!
let userId = comment[userIdRange]
let usernameRange = match.range(at: 1)
attributedString.addAttribute(NSAttributedString.Key.link, value: URL(string: "test://profile/\(userId)")!, range: usernameRange)
}
print(attributedString)
The result right now can be represented like this, when printed:
Hello {
}#kevin{
NSLink = "test://profile/1";
}[1], #john and {
}#andrew{
NSLink = "test://profile/2";
}[2]!{
}
So #kevin and #andrew are links, #john is not (which is expected!), but the user ids are still visible. Surely this is a problem that has been solved before but I can't find any examples, not sure what keywords to search for. There are plenty of questions about detecting usernames/mentions in strings, and even more about making links in NSAttributedString, but that's not the problem I am trying to solve.
How would I turn the #username[userid] mentions into clickable #username links, so that the [userid] part is hidden?

Answer 1

You just need to get all the matching ranges, iterate them in reverse order, add the link to it and then replace the whole range with the name. Something like:
let comment = "Hello #kevin[1], #john and #andrew[2]!"
let attributedString = NSMutableAttributedString(string: comment)
let regex = try NSRegularExpression(pattern: #"(#[\w.-#]+)\[(\d+)\]"#)
var ranges: [(NSRange,NSRange,NSRange)] = []
regex.enumerateMatches(in: comment, range: NSRange(comment.startIndex..., in: comment)) { match, _, _ in
guard let match = match else {
return
}
ranges.append((match.range(at: 0),
match.range(at: 1),
match.range(at: 2)))
}
ranges.reversed().forEach {
let userId = attributedString.attributedSubstring(from: $0.2).string
let username = attributedString.attributedSubstring(from: $0.1).string
attributedString.addAttribute(.link, value: URL(string: "test://profile/\(userId)")!, range: $0.0)
attributedString.replaceCharacters(in: $0.0, with: username)
}
print(attributedString)
This will print
Hello {
}#kevin{
NSLink = "test://profile/1";
}, #john and {
}#andrew{
NSLink = "test://profile/2";
}!{
}

Answer 2

Quickly done:
let comment = "Hello #kevin[1], #john and #andrew[2]!"
let attributedString = NSMutableAttributedString(string: comment)
let wholeRange = NSRange(attributedString.string.startIndex..<attributedString.string.endIndex, in: attributedString.string)
let regex = try NSRegularExpression(pattern: #"(#[\w.-#]+)\[(\d+)\]"#)
let matches = regex.matches(in: attributedString.string, options: [], range: wholeRange)
matches.reversed().forEach { aResult in
let fullMatchRange = Range(aResult.range(at: 0), in: attributedString.string)! //#kevin[1]
let replacementRange = Range(aResult.range(at: 1), in: attributedString.string)! //#kevin
let userIdRange = Range(aResult.range(at: 2), in: attributedString.string)! // 1
let atAuthor = String(attributedString.string[replacementRange])
attributedString.addAttribute(.link,
value: URL(string: "test://profile/\(attributedString.string[userIdRange])")!,
range: NSRange(fullMatchRange, in: attributedString.string))
attributedString.replaceCharacters(in: NSRange(fullMatchRange, in: attributedString.string),
with: atAuthor)
}
print(attributedString)
Output:
Hello {
}#kevin{
NSLink = "test://profile/1";
}, #john and {
}#andrew{
NSLink = "test://profile/2";
}!{
}
What's to see:
I changed the pattern, for easy captures. See the sample in comment in the forEach().
I used matches in reverse order, else the ranges won't be accurate anymore!
I kept playing with attributedString.string instead of comment in case it's "unsync".