In Swift how do you simply "make a variable" a RegexComponent?

May 17, 2023

I have code like this …

func blah() {
  if let r = someString.firstMatch(of: /([abc])(\d{2})$/) {
    blah blah .. String(r.1), String(r.2)
  }
}

Normally with a regex, i’d just keep the regex-guts as a variable.

Hence, something like this:

let RX: RegexComponent = /([abc])(\d{2})$/

func blah() {
  if let r = someString.firstMatch(of: RX) { ..
}

I have completely and absolutely failed to be able to do this, and have searched for hours.

some suggest you need any RegexComponent

let RX: any RegexComponent = /([abc])(\d{2})$/

func blah() {
  if let r = someString.firstMatch(of: RX) { ..
}

But it simply doesn’t work.

the argument of firstMatch#of is undoubtedly a RegexComponent.

How the heck can I make/set a variable that is a RegexComponent ??

>Solution :

This should do the trick:

let RX = /([abc])(\d{2})$/

Now, since it works, you can Alt+click on the var name (RX), and the type inference (ie, type of the variable "deduced" by the compiler) should tell you it’s a Regex<Substring>

So you can write also:

let RX: Regex<Substring> = /([abc])(\d{2})$/

I don’t have the full explanation, since I haven’t played with the new Regex, but I guess it’s because RegexComponent is protocol, so there is no really an init, and there must be something with "literals" (or assimilated).