Generating dummy string with random characters in Swift

String.swift

import Foundation

extension String {
	
	static func random(in length: UInt, characterSource: [Int]? = nil) -> String {
		let charcodes: [Int]
		if let characterSource {
			charcodes = characterSource
		}
		else {
			let numbers = Array(0x0030...0x0039)
			let alphabet = Array(0x0041...0x005A) + Array(0x0061...0x007A)
			charcodes = numbers + alphabet
		}
		
		let dummyLetters = charcodes.compactMap {
			if let scalar = UnicodeScalar($0) {
				return String(scalar)
			}
			return nil
		}
		
		var dummyString = ""
		for _ in 0..<length {
			dummyString += String(dummyLetters.randomElement() ?? "")
		}
		
		return dummyString
}

let numbers = Array(0x0030...0x0039)
let alphabet = Array(0x0041...0x005A) + Array(0x0061...0x007A)
let katakana = Array(0x30A1...0x30FC)
let characters = numbers + alphabet + katakana

let randomString = String.random(in: 10, characterSource: characters)

ソ1ッk2ヘlPナc
SPポtpチシJヰM
shルァヒヅネズHビ
ゴHツセMエSーUイ
iァホォナベャーシ7
プバロゥーNォヨベゴ