奇怪的String.unicodeScalars和CharacterSet行为

Question

我正在尝试使用Swift 3 CharacterSet来过滤字符,String但是我很早就陷入了困境.CharacterSet有一个名为的方法contains

func包含(_ member:UnicodeScalar) - > Bool
测试CharacterSet中特定UnicodeScalar的成员资格.

但测试这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")
}

我已经到了Capital A is not in the group of capital letters,我期待相反的事情.

非常感谢.

Answer 1

CharacterSet.capitalizedLetters 返回一个字符集,其中包含Unicode General Category Lt aka"Letter,titlecase"中的字符.这是"包含大写字母后跟小写字母的连字符(例如,Dž,Lj,Nj和Dz)"(比较 维基百科:Unicode字符属性或 Unicode®标准附件#44 - 表12. General_Category值).

你可以在这里找到一个列表:'Letter,Titlecase'类别中的Unicode字符.

您还可以使用来自NSCharacterset的NSArray中的代码 来转储字符集的内容:

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())

// ["?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?", "?"]

你可能想要的是CharacterSet.uppercaseLetters哪个

返回包含Unicode General Category Lu和Lt中字符的字符集.