如何使用swift识别字符串中的大写和小写字符?

Question

这是我目前所做的(用于测试目的):

let string = "The quick BroWn fOX jumpS Over tHe lazY DOg"
for chr in string {
    if isupper(String(chr)) {
        print(String(chr).lowercaseString)
        continue
    }
    print(chr)
}

如何测试大写和小写字符?

我知道我可以从swift调用C函数，但这似乎不适合我。我怎么能做到这一点与swift只?

Answer 1

我不确定你试图避免使用C函数是什么意思。我希望这不会包括在开发应用程序时避开OS X和iOS提供的框架和基础库，例如，ncharacter set类，它提供了你在Unicode兼容实现中所需要的东西。

扩展Matt的回答，让它更接近你问题的要求:

import UIKit
let testString = "Åke röstet un café in Владивосток!"
let lowerCase = NSCharacterSet.lowercaseLetterCharacterSet()
let upperCase = NSCharacterSet.uppercaseLetterCharacterSet()
for currentCharacter in testString.utf16 {
  if lowerCase.characterIsMember(currentCharacter) {
    println("Character code (currentCharacter) is lowercase.")
  } else if upperCase.characterIsMember(currentCharacter) {
    println("Character code (currentCharacter) is UPPERCASE.")
  } else {
    println("Character code (currentCharacter) is neither upper- nor lowercase.")
  }
}

迅速

3

let testString = "Åke röstet un café in Владивосток!"
let lowerCase = CharacterSet.lowercaseLetters
let upperCase = CharacterSet.uppercaseLetters
for currentCharacter in testString.unicodeScalars {
    if lowerCase.contains(currentCharacter) {
        print("Character code (currentCharacter) is lowercase.")
    } else if upperCase.contains(currentCharacter) {
        print("Character code (currentCharacter) is UPPERCASE.")
    } else {
        print("Character code (currentCharacter) is neither upper- nor lowercase.")
    }
}

Answer 2

在Swift 5中，我们现在可以根据Unicode标准检查字符属性。

对于你的问题，chr.isUppercase和chr.isLowercase是答案。

Answer 3

您总是可以看到小写表示是否与当前值不同;

let string = "The quick BroWn fOX jumpS Over tHe lazY DOg"
var output = ""
for chr in string {
    var str = String(chr)
    if str.lowercaseString != str {
        output += str
    }
}
print(output)
>>> TBWOXSOHYDO

Answer 4

通过扩展String和Character，我认为我已经达到了一个相当灵活的解决方案，完全(?)Unicode意识。下面的语法适用于Swift 3.0。虽然在Swift 2.x中没有什么是不可能的

extension String {
    func isUppercased(at: Index) -> Bool {
        let range = at..<self.index(after: at)
        return self.rangeOfCharacter(from: .uppercaseLetters, options: [], range: range) != nil
    }
}
extension Character {
    var isUppercase: Bool {
      let str = String(self)
      return str.isUppercased(at: str.startIndex)
    }
}
let str = "AaÀàΓγ!2😂🇺🇸"
let uppercase = str.characters.filter({ $0.isUppercase }) // ["A", "À", "Γ"]
for char in str.characters {
    "(char): (char.isUppercase)"
}
// A: true
// a: false
// À: true
// à: false
// Γ: true
// γ: false
// !: false
// 2: false
// 😂: false
// 🇺🇸: false

这些扩展的TODO是在Character上重构isUppercase以不转换为String。

Answer 5

在Swift 3中，我做了这样的事情

import UIKit
...
let ch = "A".unicodeScalars.first!
let is_ch_upperCase = CharacterSet.uppercaseLetters.contains(ch)

Answer 6

SWIFT 4:

你可以简单地不需要所有其他花哨的东西，除非你要检查数字或unicode标量等:

extension String {
   var isLowercase: Bool {
       return self == self.lowercased()
   }
   var isUppercase: Bool {
       return self == self.uppercased()
   }
}

Answer 7

更简洁，但可能比循环慢:

let str = "The quick BroWn fOX jumpS Over tHe lazY DOg"
let nonUpperCase = NSCharacterSet.uppercaseLetterCharacterSet().invertedSet
let letters = str.componentsSeparatedByCharactersInSet(nonUpperCase)
"".join(letters) // "TBWOXSOHYDO"

Answer 8

在Bob Prystaneks函数的基础上展开，你可以扩展Swift的"Character"类。只需将以下扩展名放在代码中的任何位置，现在您可以询问任何字符是否大写。

extension Character
{
    public func isUpper() -> Bool
    {
        let characterString = String(self)
        return (characterString == characterString.uppercaseString) && (characterString != characterString.lowercaseString)
    }
}

Answer 9

简单扩展接受任何CharacterSet检查:

extension String {
    func hasCharacter(in characterSet: CharacterSet) -> Bool {
        return rangeOfCharacter(from: characterSet) != nil
    }
}

用法:

"aBc".hasCharacter(in: .lowercaseLetters)
"aBc".hasCharacter(in: .uppercaseLetters)
"aBc".hasCharacter(in: <#AnyOtherCharacterSetYouWant#>)

Answer 10

添加这个Swift扩展，这样字符类的所有实例都有两个新函数:isUpperCase()测试字符是否是大写的，isLowerCase()测试字符是否是小写的。该实现只是检查字符实例是否在所需的集合中。

extension Character {
        func isUpperCase() -> Bool {
            return CharacterSet.uppercaseLetters.contains(self.unicodeScalars.first!)
        }
        func isLowerCase() -> Bool {
            return CharacterSet.lowercaseLetters.contains(self.unicodeScalars.first!)
        }
  }

Answer 11

let string = "The quick BroWn fOX jumpS Over tHe lazY DOg"
for (_,ch) in string.enumerated() {
    if ch.isUppercase {
         //uppercase
   } else {
        //lowercase: ch.isLowercase
   }
}

迅速4枚举一个字符串并获取字符的ascii码，然后进行比较。

的ascii码

→97 b ->98…

→65 B ->66…

let string = "The quick BroWn fOX jumpS Over tHe lazY DOg"
for (_,ch) in string.enumerated() {
    let chValue = String(ch).unicodeScalars
    let asciiValue = chValue[chValue.startIndex].value
    if asciiValue >= 97 {
           //lowercase
    } else {
           //uppercase
    }
}

Answer 12

正如其他人所评论的那样，仅使用uppercaseString或lowercaseString不会考虑"非alpha"字符。

这就是我实现isupper的方式。只有当一个字符不等于它的小写字母时，它才是大写字母。

func isupper(c:Character) -> Bool
{
    let cs = String(c)
    return (cs == cs.uppercaseString) && (cs != cs.lowercaseString)
}

Answer 13

创建并使用这个扩展:

extension Character {
    var isUppercase: Bool {
        guard self.asciiValue != nil else {
            return false
        }
        return self.asciiValue! >= Character("A").asciiValue! &&
                self.asciiValue! <= Character("Z").asciiValue!
    }
    var asciiValue: UInt32? {
        return String(self).unicodeScalars.first?.value
    }
}

Answer 14

每个字符都可以表示一个UTF或Unicode值(8/16/21 Bit):

例如:

UTF-8 "Dog!": 68, 111, 103, 33
Unicode (Dog Face): U+1F436

如果你想检查大小写，你可以匹配UTF范围

(PS:注意不同的UTF-XX/Unicode格式)

Answer 15

创建并使用这个扩展:

extension Character {
        var isUppercase: Bool {
            return (String(self).unicodeScalars.filter {
                $0.value >= "A".unicodeScalars.first!.value &&
                $0.value <= "Z".unicodeScalars.first!.value
            }).count != 0
        }
    }

Answer 16

Swift 3:

var str = "Hello"
let upperChars = str.unicodeScalars.flatMap({ char in
    CharacterSet.uppercaseLetters.contains(char) ? char : nil
})
let lowerChars = str.unicodeScalars.flatMap({ char in
    CharacterSet.lowercaseLetters.contains(char) ? char : nil
})
// upperChars -> ["H"]
// lowerChars -> ["e", "l", "l", "o"]

Answer 17

Simple Swifty extension:

extension String {
    var isLower: Bool {
        return String(self.filter { String($0) == String($0).lowercased() }) == self
    }
}

Answer 18

检查字符串是否包含大写，小写或特殊字符:

let lowerCase = CharacterSet.lowercaseLetters
let upperCase = CharacterSet.uppercaseLetters
let numbers = CharacterSet.decimalDigits
let containsNumbers = text.unicodeScalars.contains(where: { numbers.contains($0) })
let containsLowerCase = text.unicodeScalars.contains(where: { lowerCase.contains($0) })
let containsUpperCase = text.unicodeScalars.contains(where: { upperCase.contains($0) })
let containsSpecial = text.unicodeScalars.contains(where: { !lowerCase.contains($0) && !upperCase.contains($0) && !numbers.contains($0) })