将 UInt32 (UTF-32) 转换为 Swift 中的字符串

Question

我有一个 UInt32 值数组。我想将此数组转换为 String.

这行不通：

let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049]
let myString = String(myUInt32Array) // error
let myString = String(stringInterpolationSegment: myUInt32Array) // [72, 101, 108, 108, 111, 128049] (not what I want)

这些 SO 帖子显示 UTF8 和 UTF16：

How can I create a String from UTF8 in Swift?
Is there a way to create a String from utf16 array in swift?

Answer 1

UnicodeScalar 是 UInt32 的类型别名。因此，将您的 UInt32 值转换为 UnicodeScalar，然后将它们附加到 String.

let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049]

var myString: String = ""

for value in myUInt32Array {
    if let scalar = UnicodeScalar(value) {
        myString.append(Character(scalar))
    }
}

print(myString) // Hello

Answer 2

（答案已更新 Swift 4 及更高版本。）

使用 Swift 类型 Data 和 String 这可以像

let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049, 127465, 127466]
let data = Data(bytes: myUInt32Array, count: myUInt32Array.count * MemoryLayout<UInt32>.stride)
let myString = String(data: data, encoding: .utf32LittleEndian)!
print(myString) // Hello

此处使用强制解包，因为从 UTF-32 转换而来指向字符串的代码不能失败。

为了方便起见，您可以定义一个 String 扩展名

extension String {
    init(utf32chars:[UInt32]) {
        let data = Data(bytes: utf32chars, count: utf32chars.count * MemoryLayout<UInt32>.stride)
        self = String(data: data, encoding: .utf32LittleEndian)!
    }
}

并将其用作

let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049, 127465, 127466]
let myString = String(utf32chars: myUInt32Array)
print(myString) // Hello

为了完整起见，通用转换器来自

extension String {
    init?<C : UnicodeCodec>(codeUnits:[C.CodeUnit], codec : C) {
        var codec = codec
        var str = ""
        var generator = codeUnits.makeIterator()
        var done = false
        while !done {
            let r = codec.decode(&generator)
            switch (r) {
            case .emptyInput:
                done = true
            case .scalarValue(let val):
                str.unicodeScalars.append(val)
            case .error:
                return nil
            }
        }
        self = str
    }
}

可用于 UTF-8、UTF-16 和 UTF-32 输入。在你的情况下它将是

let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049, 127465, 127466]
let myString = String(codeUnits: myUInt32Array, codec : UTF32())!
print(myString) // Hello

将 UInt32 (UTF-32) 转换为 Swift 中的字符串

Convert UInt32 (UTF-32) to String in Swift

string

uint32

ios

swift