Поиск подстроки в строке (текст поиск подстрока строка find string sub subString text) - Swift 5

if let range = mystring.range(of: "this") {

let startPos = mystring.distance(from: mystring.startIndex, to: range.lowerBound)
let endPos = mystring.distance(from: mystring.startIndex, to: range.upperBound)

print(startPos, endPos)
}
// 2й вариант применения
let mystring = "hi this is my name"
if let range = mystring.range(of: "this") {
print("Find success!")
}
// 3й вариант применения
let mystring = "hi this is my name"
if (mystring?.range(of: "true")) != nil {
print("Отправлено!")
}