如何在Swift 4中过滤字符串中的字符

Question

在下面的Swift 3代码中,我从字符串中提取所有数字,但我无法弄清楚如何在Swift 4中做同样的事情.

var myString = "ABC26FS464"

let myNumbers = String(myString.characters.filter { "01234567890".characters.contains($0)})

print(myNumbers) // outputs 26464

如何从Swift 4中的字符串中提取所有数字？

Answer 1

Swift 4使它更简单一些.只需删除.characters并使用

let myNumbers = myString.filter { "0123456789".contains($0) }

但要真正做到这一点,你可以使用decimalDigits字符集......

let digitSet = CharacterSet.decimalDigits
let myNumbers = String(myString.unicodeScalars.filter { digitSet.contains($0) })

Answer 2

最简单：

由于“Character”几乎具有所有最常用的带有“.isXY”计算属性的字符检查，因此您可以使用此模式，这似乎是进行字符串过滤的最方便、最快捷的方法。

/// Line by line explanation.
let str = "Stri1ng wi2th 3numb4ers".filter(\.isNumber) // "1234"
let int = Int(str)                                     // Optional<Int>(1234)
let unwrappedInt = int!                                // 1234

/// Solution.
extension String {

    /// Numbers in the string as Int.
    /// 
    /// If doesn't have any numbers, then 0.
    var numbers: Int {
        Int(filter(\.isNumber)) ?? 0
    }

    /// Numbers in the string as Int.
    ///
    /// If doesn't have any numbers, then nil.
    var optionalNumbers: Int? {
        Int(filter(\.isNumber))
    }
}