Swift 中字符串基本知识（一）- Character

Character 是什么？

Apple 官方文档定义：

A single extended grapheme cluster that approximates a user-perceived character.

单一扩展字符群，用来表示用户可以感知的字符。

简单的说就是用来表示单个字符的结构体。

具体实现代码如下（省略了一些代码和修饰符）：

public struct Character {
    /// Creates a character containing the given Unicode scalar value.
    public init(_ content: Unicode.Scalar)

    /// Creates a character from a single-character string.
    public init(_ s: String)

    /// The ASCII encoding value of this character, if it is an ASCII character.
    public var asciiValue: UInt8? { get }
}

怎么使用？

怎么初始化一个字符 Character？

1. 使用 Unicode 标量值

let airplane = Unicode.Scalar(9992)!
let character = Character(airplane)
print(character)
// ✈

2. 使用单个字符的字符串

let exclamationMark: Character = "!"
// or 
let exclamationMark = Character("!")

怎么和字符串 String 一起使用？

1. 字符串和字符数组如何相互转化

字符串转字符数组

let string = "Dog!🐶"
let characters = Array(string) // Array<Character>
print(characters)
// ["D", "o", "g", "!", "🐶"]

字符数组转字符串

let characters: [Character] = ["D", "o", "g", "!", "🐶"]
let string = String(characters)
print(string)
// "Dog!🐶"

2. 字符串如何遍历所有字符

let string = "Dog!🐶"
for character in string {
    print(character)
}
// D
// o
// g
// !
// 🐶

3. 如何得到字符串中指定 index 的字符？

func getChar(s: String, at offset: Int) -> Character {
    let index = s.index(s.startIndex, offsetBy: offset)
    return s[index]
}

参考链接

• Strings and Characters