Swift中带字符串的整型求和

let str = "123"
if let num = Int(str) {
    let sum = num + 456
    print(sum)
} else {
    print("无法将字符串转换为整数")
}

let str = "123 456"
let scanner = Scanner(string: str)
var sum = 0
while scanner.scanInt() != nil {
    sum += scanner.scanInt() ?? 0
}
print(sum)

import Foundation

let str = "123 456"
let regex = try! NSRegularExpression(pattern: "\\d+")
let matches = regex.matches(in: str, range: NSRange(str.startIndex..., in: str))
var sum = 0
for match in matches {
    if let range = Range(match.range, in: str), let num = Int(str[range]) {
        sum += num
    }
}
print(sum)