Swift：格式化字符串宽度

我想要做的是在C/C++, Java和许多其他语言中非常简单.我想要做的就是能够指定字符串的宽度,类似于：

printf("%-15s", var);

这将创建15个字符的字段宽度.我做了很多谷歌搜索.我已经尝试过使用COpaquepointeras和String(格式：以各种方式没有运气.任何建议都会非常感激.我可能在谷歌搜索时遗漏了一些东西.

你最好自己动手

let str0 = "alpha"
let length = 20
// right justify
var str20r = String(count: (length - str0.characters.count), repeatedValue: Character(" "))
str20r.appendContentsOf(str0)
// "               alpha"

// left justify
var str20l = str0
str20l.appendContentsOf(String(count: (length - str0.characters.count), repeatedValue: Character(" ")))
// "alpha               "

如果你需要更“一般”的东西

func formatString(str: String, fixLenght: Int, spacer: Character = Character(" "), justifyToTheRigth: Bool = false)->String {
    let c = str.characters.count
    let start = str.characters.startIndex
    let end = str.characters.endIndex
    var str = str
    if c > fixLenght {
        switch justifyToTheRigth {
        case true:
            let range = start.advancedBy(c - fixLenght)..<end
            return String(str.characters[range])
        case false:
            let range = start..<end.advancedBy(fixLenght - c)
            return String(str.characters[range])
        }
    } else {
        var extraSpace = String(count: fixLenght - c, repeatedValue: spacer)
        if justifyToTheRigth {
            extraSpace.appendContentsOf(str)
            return extraSpace
        } else {
            str.appendContentsOf(extraSpace)
            return str
        }
    }
}

let str = "ABCDEFGH"
let s0 = formatString(str, fixLenght: 3)
let s1 = formatString(str, fixLenght: 3, justifyToTheRigth: true)
let s2 = formatString(str, fixLenght: 10, spacer: Character("-"))
let s3 = formatString(str, fixLenght: 10, spacer: Character("-"), justifyToTheRigth: true)

print(s0)
print(s1)
print(s2)
print(s3)

打印

ABC
FGH
ABCDEFGH--
--ABCDEFGH