对于Swift中的字符,isDigit()的替换是什么？

Question

正如提到的这个帖子,之前的Xcode 6 Beta 4的,可以使用c.isDigit(),并c.isAlpha()找到,如果c : Character是一个数字或字母.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？如果没有使用用于字母数字选项的switch语句设置函数,我该如何测试其数字上的字符？

Answer 1

"问题"是Swift字符不直接对应于Unicode代码点,而是表示"扩展字形集群",它可以包含多个Unicode标量.例如

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

实际上是两个 Unicode标量的序列.

如果我们忽略这个事实,那么你可以检索字符的初始 Unicode标量(比较如何获得字符的Unicode代码点？)并测试其在字符集中的成员资格:

let c : Character = "5"

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

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

这对于字符"0"..."9"返回"true",但实际上对于"十进制数字类别"的所有 Unicode标量,例如:

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

如果你只关心(ASCII)数字"0"..."9",那么最简单的方法可能是:

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

或者,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

使用Swift 5，您可以根据需要选择以下方式之一来解决问题。

＃1。使用Character的isNumber属性

角色具有称为的属性isNumber。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以下方法检查字符是否代表数字isNumber：

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

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

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

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

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

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

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

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

＃2。使用Character的isWholeNumber属性

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

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

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

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

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

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

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

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

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

＃3。使用Unicode.Scalar.Properties的generalCategory属性和Unicode.GeneralCategory.decimalNumber

下图显示了样品游乐场代码如何检查如果一个字符的第一个Unicode标是使用十进制数generalCategory和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 = "?"
let scalar = character.unicodeScalars.first! // CIRCLED DIGIT FOUR
print(scalar.properties.generalCategory == .decimalNumber) // false

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

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

let character: Character = "?"
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

let character: Character = "F"
let scalar = character.unicodeScalars.first! // LATIN CAPITAL LETTER F
print(scalar.properties.generalCategory == .decimalNumber) // false

＃4。使用Unicode.Scalar.Properties的generalCategory属性和Unicode.GeneralCategory.otherNumber

同样，你可以检查一个字符对应的第一个Unicode标到类别Other_Number Unicode标准使用generalCategory和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 = "?"
let scalar = character.unicodeScalars.first!
print(scalar.properties.generalCategory == .otherNumber) // true

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

let character: Character = "1??"
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

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

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

＃5。使用CharacterSet的decimalDigits属性

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

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

import Foundation

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

import Foundation

let character: Character = "1??"
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

import Foundation

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

import Foundation

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

＃6。使用Unicode.Scalar.Properties的numericType

Apple文档指出numericType：

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nil。

以下示例代码示出了可能的数值类型（decimal，digit或numeric对于给定字符的第一个标量）：

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

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

let character: Character = "1??"
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)

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

let character: Character = "F"
let scalar = character.unicodeScalars.first!
print(scalar.properties.numericType) // nil