1. 什么是字符？
字符(Character)就是一个简单的符号（字母:abc, 数组:123等）。在swift种使用如下方式定义字符类型，
let someCharacter: Character
1.1 怎样定义字符并赋值
为字符串赋值可以通过let aStr: String = " "，为字符赋值也是一样，let aCharacter: Character = " "但是一个字符变量只能包含一个空格。
所以，如果你定义的变量包含多个字符，则应该使用String，而不是Character。
1.1.1 举例1: 定义并赋值字符
let someCharacter: Character = "H"
let specialCharacter: Character = "@" // 特殊字符
print(someCharacter)
print(specialCharacter)
1.1.2 举例2: 定义字符，并赋值多个字符（报错）
如果尝试为一个字符变量赋值两个字符，则会报错，如下代码所示，
let fialableCharacter: Character = @"H@"
// 用String类型替代Character
let okString: String = @"H@"
1.2 使用unicode和转移字符创建Character
开发这可以使用unicode创建特殊的字符类型，例如创建emoji表情字符。创建一个unicode需要使用转移字符，例如\u{n}，n是十六进制的数字。如下代码所示，
let heartShape: Character = "\u{2655}"
print(heartShape)
// 输出：♥
在这个例子总，一个星形的字符使用U+2655 unicode创建。虽然"{2655}"包裹在双引号种，编译器并不会把它当作字符串，因为我们使用了“转移字符{u}”。一个转移字符并不代表它字面上的含义。
2. 字符常用扩展属性和方法
如下方法参考github的SwifterSwift项目，读者可查看了解更多的细节。
import UIKit
// MARK: - Properties
public extension Character {
/// Check if character is emoji
/// - example: Character("😊").isEmoji -> true
public var isEmoji: Bool {
let scalarValue = String(self).unicodeScalars.first!.value
switch scalarValue {
case 0x3030, 0x00AE, 0x00A9, // Special Character > 特殊字符
0x1D000...0x1F77F, // Emoticons > 情感符
0x2100...0x27BF, // Misc symbols and Dingbats >
0xFE00...0xFE0F, // Variation Selectors > 变异选择符
0x1F900...0x1F9FF: // Supplemental Symbols and Pictographs > 补充的符号和象形文字
return true
default:
return false
}
}
/// Check if character is number
/// - example: Character("1").isNummber
public var isNumber: Bool {
return Int(String(self)) != nil
}
/// Check if character is a letter(字母)
/// - example: (1) Character("4").isLetter -> false, (2) Character("a").isLetter -> True
public var isLetter: Bool {
return String(self).rangeOfCharacter(from: .letters, options: .numeric, range: nil) != nil
}
/// Check if character is lowercased
/// - example: (1) Character("a").isLowercased -> true, (2) Character("A").isLowercased -> false
public var isLowercased: Bool {
return String(self) == String(self).lowercased()
}
/// Check if character is uppercased
/// - example: (1) Character("a").isUppercased -> true, (2) Character("A").isUppercased -> true
public var isUppercased: Bool {
return String(self) == String(self).uppercased()
}
/// Check if character is white space(空格)
/// - example: (1) Character(" ").isWhiteSpace -> true, (2) Character("A").isWhiteSpace -> false
public var isWhiteSpace: Bool {
return String(self) == " "
}
/// Integer value from character (if applicable)
/// - example: (1) Character("1").int -> 1, (2) Character("A").int -> nil
public var int: Int? {
return Int(String(self))
}
// String value from character
public var string: String {
return String(self)
}
/// Return the character lowercased
public var lowercased: Character {
return String(self).lowercased().first!
}
/// Return the character uppercased
public var uppercased: Character {
return String(self).uppercased().first!
}
}
// MARK: - Methods
public extension Character {
/// Random character
// public static func randomAlphanumeric() -> Character {
// return "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".randomElement()!
// }
}
// MARK: - Operater
public extension Character {
/// Repeat character multiple times
/// - example: Character("=") * 10 -> "=========="
/// - Parameters:
/// - lhs: charater to repeat.
/// - rhs: number of times to repeat character.
/// - Returns: strign with charater repeated n times.
public static func * (lhs: Character, rhs: Int) -> String {
guard rhs > 0 else { return "" }
return String(repeating: String(lhs), count: rhs)
}
/// Repeat character mltiple tiems
/// - exmaple: 10 * Character("-") -> "----------"
/// - Parameter:
/// - lhs: number of times to repeat character.
/// - rhs: character to repeat
/// - Returns: string with character repeated n times
public static func * (lhs: Int, rhs: Character) -> String {
guard lhs > 0 else { return "" }
return String(repeating: String(rhs), count: lhs)
}
}
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