swiftcharacter-set

How to print a content of the CharacterSet.decimalDigits?

I tried to print a content of the CharacterSet.decimalDigits with:

print(CharacterSet.decimalDigits)

output: CFCharacterSet Predefined DecimalDigit Set

But my expectation was something like this:

[1, 2, 3, 4 ...]

So my question is: How to print content of the CharacterSet.decimalDigits?

Solution

  • This is not easy. Character sets are not made to be iterated, they are made to check whether a character is inside them or not. They don't contain the characters themselves and the ranges cannot be accessed.

    The only thing you can do is to iterate over all characters and check every one of them against the character set, e.g.:

    let set = CharacterSet.decimalDigits
let allCharacters = UInt32.min ... UInt32.max

allCharacters
    .lazy
    .compactMap { UnicodeScalar($0) }
    .filter { set.contains($0) }
    .map { String($0) }
    .forEach { print($0) }

    However, note that such a thing takes significant time and shouldn't be used inside a production application.