Swift 常用操作

1. Charcter 与 Int 互转

let num = strArray[index].asciiValue! - Character("0").asciiValue!
let char = Character(UnicodeScalar(num))

2. 大、小写字母转为小写字母

//  " " 空格的十进制为32，二进制为 0010 0000
"a" | " " = "a"
"A" | " " = "a"

// "_" 的十进制为95，二进制为0101 1111
"b" & "_" = "B"
"B" & "_" = "B"