对于Swift中的字符，isDigit（）的替换是什么？

Question

如this post中所述，在Xcode 6 Beta 4之前，可以使用c.isDigit()和c.isAlpha()来查找c : Character是数字还是数字。帖子提到这被删除，因为它只对ASCII字符有效。

我的问题是，什么是替代品？如果没有使用带有字母数字选项的switch语句设置函数，我该如何在数字上测试一个字符？

Answer 1

＆＃34;问题＆＃34;是Swift字符不直接对应Unicode 代码点，但代表一个＆＃34;扩展的字形集群＆＃34;哪个可以包括 多个Unicode标量。例如

let c : Character = "" // REGIONAL INDICATOR SYMBOL LETTERS US

实际上是一系列两个 Unicode标量。

如果我们忽略这个事实，那么你可以检索的初始 Unicode标量 字符（比较How can I get the Unicode code point(s) of a Character?）并在字符集中测试其成员资格：

let c : Character = "5"

let s = String(c).unicodeScalars
let uni = s[s.startIndex]

let digits = NSCharacterSet.decimalDigitCharacterSet()
let isADigit = digits.longCharacterIsMember(uni.value)

这会返回＆＃34; true＆＃34;对于角色＆＃34; 0＆＃34; ......＆＃34; 9＆＃34;，但实际上是所有 "decimal digit category"的Unicode标量，例如：

let c1 : Character = "৯" // BENGALI DIGIT NINE U+09EF
let c2 : Character = "" // MATHEMATICAL DOUBLE-STRUCK DIGIT ONE U+1D7D9

如果您只关心（ASCII）数字＆＃34; 0＆＃34; ...＆＃34; 9＆＃34;，那么最简单的方法可能是：

if c >= "0" && c <= "9" { }

或使用范围：

if "0"..."9" ~= c { }

Answer 2

Swift 3似乎更容易一些：

let str = "abcdef12345"
let digitSet = CharacterSet.decimalDigits

for ch in str.unicodeScalars {
    if digitSet.contains(ch) {
        // is digit!
    }
}

Answer 3

关于 Swift 3 ：

根据伟大的马丁R答案，对于谁有新的快速问题：

取代：

let digits = NSCharacterSet.decimalDigits as NSCharacterSet

使用：

{{1}}

Answer 4

对于单个角色：

CharacterSet.decimalDigits.contains(string.unicodeScalars.first!)

Answer 5

使用Swift 5，您可以根据需要选择以下方式之一来解决您的问题。

---

＃1。使用Character的{​​{3}}属性

字符具有一个名为isNumber的属性。 isNumber具有以下声明：

var isNumber: Bool { get }

  

一个布尔值，指示此字符是否代表数字。

下面的Playground示例代码显示了如何使用isNumber检查字符是否代表数字：

let character: Character = "9"
print(character.isNumber) // true

let character: Character = "½"
print(character.isNumber) // true

let character: Character = "④"
print(character.isNumber) // true

let character: Character = "1⃣"
print(character.isNumber) // true

let character: Character = "1️⃣"
print(character.isNumber) // true

let character: Character = "৯"
print(character.isNumber) // true

let character: Character = ""
print(character.isNumber) // true

let character: Character = "F"
print(character.isNumber) // false

---

＃2。使用Character的{​​{3}}属性

如果要检查字符是否代表整数，可以使用Character的{​​{1}}属性：

isWholeNumber

let character: Character = "9"
print(character.isWholeNumber) // true

let character: Character = "½"
print(character.isWholeNumber) // false

let character: Character = "④"
print(character.isWholeNumber) // true

let character: Character = "1⃣"
print(character.isWholeNumber) // false

let character: Character = "1️⃣"
print(character.isWholeNumber) // false

let character: Character = "৯"
print(character.isWholeNumber) // true

let character: Character = ""
print(character.isWholeNumber) // true

---

＃3。使用let character: Character = "F" print(character.isWholeNumber) // false 的{​​{3}}属性和Unicode.Scalar.Properties

下面的Playground示例代码显示了如何使用Unicode.GeneralCategory.decimalNumber和generalCategory检查字符的第一个Unicode标量是否为十进制数字：

Unicode.GeneralCategory.decimalNumber

let character: Character = "9"
let scalar = character.unicodeScalars.first! // DIGIT NINE
print(scalar.properties.generalCategory == .decimalNumber) // true

let character: Character = "½"
let scalar = character.unicodeScalars.first! // VULGAR FRACTION ONE HALF
print(scalar.properties.generalCategory == .decimalNumber) // false

let character: Character = "④"
let scalar = character.unicodeScalars.first! // CIRCLED DIGIT FOUR
print(scalar.properties.generalCategory == .decimalNumber) // false

let character: Character = "1⃣"
let scalar = character.unicodeScalars.first! // DIGIT ONE
print(scalar.properties.generalCategory == .decimalNumber) // true

let character: Character = "1️⃣"
let scalar = character.unicodeScalars.first! // DIGIT ONE
print(scalar.properties.generalCategory == .decimalNumber) // true

let character: Character = "৯"
let scalar = character.unicodeScalars.first! // BENGALI DIGIT NINE
print(scalar.properties.generalCategory == .decimalNumber) // true

let character: Character = ""
let scalar = character.unicodeScalars.first! // MATHEMATICAL DOUBLE-STRUCK DIGIT ONE
print(scalar.properties.generalCategory == .decimalNumber) // true

---

＃4。使用let character: Character = "F" let scalar = character.unicodeScalars.first! // LATIN CAPITAL LETTER F print(scalar.properties.generalCategory == .decimalNumber) // false 的{​​{3}}属性和Unicode.Scalar.Properties

类似地，您可以使用Unicode.GeneralCategory.otherNumber和generalCategory检查字符的第一个Unicode标量与Unicode标准中的类别 Other_Number 相对应：

Unicode.GeneralCategory.otherNumber

let character: Character = "9"
let scalar = character.unicodeScalars.first!
print(scalar.properties.generalCategory == .otherNumber) // false

let character: Character = "½"
let scalar = character.unicodeScalars.first!
print(scalar.properties.generalCategory == .otherNumber) // true

let character: Character = "④"
let scalar = character.unicodeScalars.first!
print(scalar.properties.generalCategory == .otherNumber) // true

let character: Character = "1⃣"
let scalar = character.unicodeScalars.first!
print(scalar.properties.generalCategory == .otherNumber) // false

let character: Character = "1️⃣"
let scalar = character.unicodeScalars.first!
print(scalar.properties.generalCategory == .otherNumber) // false

let character: Character = "৯"
let scalar = character.unicodeScalars.first!
print(scalar.properties.generalCategory == .otherNumber) // false

let character: Character = ""
let scalar = character.unicodeScalars.first!
print(scalar.properties.generalCategory == .otherNumber) // false

---

＃5。使用let character: Character = "F" let scalar = character.unicodeScalars.first! print(scalar.properties.generalCategory == .otherNumber) // false 的{​​{3}}属性

或者，您可以导入Foundation并检查CharacterSet是否包含字符的第一个Unicode标量：

CharacterSet.decimalDigits

import Foundation

let character: Character = "9"
let scalar = character.unicodeScalars.first!
print(CharacterSet.decimalDigits.contains(scalar)) // true

import Foundation

let character: Character = "½"
let scalar = character.unicodeScalars.first!
print(CharacterSet.decimalDigits.contains(scalar)) // false

import Foundation

let character: Character = "④"
let scalar = character.unicodeScalars.first!
print(CharacterSet.decimalDigits.contains(scalar)) // false

import Foundation

let character: Character = "1⃣"
let scalar = character.unicodeScalars.first!
print(CharacterSet.decimalDigits.contains(scalar)) // true

import Foundation

let character: Character = "1️⃣"
let scalar = character.unicodeScalars.first!
print(CharacterSet.decimalDigits.contains(scalar)) // true

import Foundation

let character: Character = "৯"
let scalar = character.unicodeScalars.first!
print(CharacterSet.decimalDigits.contains(scalar)) // true

import Foundation

let character: Character = ""
let scalar = character.unicodeScalars.first!
print(CharacterSet.decimalDigits.contains(scalar)) // true

---

＃6。使用import Foundation let character: Character = "F" let scalar = character.unicodeScalars.first! print(CharacterSet.decimalDigits.contains(scalar)) // false 的{​​{3}}

Apple文档中关于Unicode.Scalar.Properties的声明：

  

对于表示数字的标量，numericType是标量的数字类型。对于所有其他标量，此属性为numericType。

以下示例代码显示给定字符的第一个标量的可能数字类型（nil，decimal或digit）：

numeric

let character: Character = "9"
let scalar = character.unicodeScalars.first!
print(scalar.properties.numericType) // Optional(Swift.Unicode.NumericType.decimal)

let character: Character = "½"
let scalar = character.unicodeScalars.first!
print(scalar.properties.numericType) // Optional(Swift.Unicode.NumericType.numeric)

let character: Character = "④"
let scalar = character.unicodeScalars.first!
print(scalar.properties.numericType) // Optional(Swift.Unicode.NumericType.digit)

let character: Character = "1⃣"
let scalar = character.unicodeScalars.first!
print(scalar.properties.numericType) // Optional(Swift.Unicode.NumericType.decimal)

let character: Character = "1️⃣"
let scalar = character.unicodeScalars.first!
print(scalar.properties.numericType) // Optional(Swift.Unicode.NumericType.decimal)

let character: Character = "৯"
let scalar = character.unicodeScalars.first!
print(scalar.properties.numericType) // Optional(Swift.Unicode.NumericType.decimal)

let character: Character = ""
let scalar = character.unicodeScalars.first!
print(scalar.properties.numericType) // Optional(Swift.Unicode.NumericType.decimal)

Answer 6

我创建了我的var来检查字符是否为数字。

var isNumber : Bool {
    get{
        return !self.isEmpty && self.rangeOfCharacter(from: CharacterSet.decimalDigits.inverted) == nil
    }
}

//使用

var initial = "1"
if let isNum = initial.isNumber, isNum { // true
    initial = "#"
}