swift - 奇怪的 String.unicodeScalars 和 CharacterSet 行为

Question

我正在尝试使用 Swift 3 CharacterSet 从 String 中过滤出字符，但我很早就陷入困境。 CharacterSet 有一个名为 contains

的方法

func contains(_ member: UnicodeScalar) -> Bool
Test for membership of a particular UnicodeScalar in the CharacterSet.

但是测试它不会产生预期的行为。

let characterSet = CharacterSet.capitalizedLetters

let capitalAString = "A"

if let capitalA = capitalAString.unicodeScalars.first {
    print("Capital A is \(characterSet.contains(capitalA) ? "" : "not ")in the group of capital letters")
} else {
    print("Couldn't get the first element of capitalAString's unicode scalars")
}

我得到 Capital A is not in the group of capital letters 但我期望相反。

非常感谢。

Answer 1

CharacterSet.capitalizedLetters返回一个字符集，其中包含 Unicode 通用类别 Lt 中的字符，又名“Letter, titlecase”。那是“包含大写字母后跟小写字母的连字(例如 Dž、Lj、Nj 和 Dz)”(比较 Wikipedia: Unicode character property 或 Unicode® Standard Annex #44 – Table 12. General_Category Values ).

您可以在此处找到列表:Unicode Characters in the 'Letter, Titlecase' Category .

您还可以使用来自 NSArray from NSCharacterset转储字符的内容设置:

extension CharacterSet {
    func allCharacters() -> [Character] {
        var result: [Character] = []
        for plane: UInt8 in 0...16 where self.hasMember(inPlane: plane) {
            for unicode in UInt32(plane) << 16 ..< UInt32(plane + 1) << 16 {
                if let uniChar = UnicodeScalar(unicode), self.contains(uniChar) {
                    result.append(Character(uniChar))
                }
            }
        }
        return result
    }
}

let characterSet = CharacterSet.capitalizedLetters
print(characterSet.allCharacters())

// ["Dž", "Lj", "Nj", "Dz", "ᾈ", "ᾉ", "ᾊ", "ᾋ", "ᾌ", "ᾍ", "ᾎ", "ᾏ", "ᾘ", "ᾙ", "ᾚ", "ᾛ", "ᾜ", "ᾝ", "ᾞ", "ᾟ", "ᾨ", "ᾩ", "ᾪ", "ᾫ", "ᾬ", "ᾭ", "ᾮ", "ᾯ", "ᾼ", "ῌ", "ῼ"]

您可能想要的是 CharacterSet.uppercaseLetters哪个

Returns a character set containing the characters in Unicode General Category Lu and Lt.