如何在Swift中使用uppercaseString，lowercaseString

Question

我有Strings，我希望用uppercaseString转换为lowercaseString，only letters。

我的琴弦;

let uppers  = " Hello*im ; + Upper+String "
let lowers  = " Hello*im ; + Lower+String "
print(uppers)
print(lowers)

大写输出看起来像这样

HELLOIMUPPERSTRING 

谢谢！

Answer 1

您可以使用Set。

let uppers  = " Hello*im ; + Upper+String "
let lowers  = " Hello*im ; + Lower+String "
let allowChars : Set<Character> = Set("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLKMNOPQRSTUVWXYZ1234567890".characters)
let upperStr = String(uppers.characters.filter {allowChars.contains($0) }).uppercaseString
let lowerStr = String(lowers.characters.filter {allowChars.contains($0) }).lowercaseString
print(upperStr)
print(lowerStr)

修改：要允许空格，还要在Set字符内添加其他字符的空格

let allowChars : Set<Character> = Set("abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLKMNOPQRSTUVWXYZ1234567890".characters)

Answer 2

首先从非字母数字字符中删除字符串，然后转换为小写或大写。

let charactersToRemove = NSCharacterSet.alphanumericCharacterSet().invertedSet
let strippedReplacement = " ".join(myString.componentsSeparatedByCharactersInSet(charactersToRemove))
let resultUppercase = strippedReplacement.uppercaseString
let resultLowercase = strippedReplacement.lowercaseString