var str = "This is my string"

print(str.replacingOccurrences(of: " ", with: "+"))

输出是

This+is+my+string

很少发生在我身上，我只是想改变字符串中的(一个单词或字符)

所以我用了字典

  extension String{
    func replace(_ dictionary: [String: String]) -> String{
          var result = String()
          var i = -1
          for (of , with): (String, String)in dictionary{
              i += 1
              if i<1{
                  result = self.replacingOccurrences(of: of, with: with)
              }else{
                  result = result.replacingOccurrences(of: of, with: with)
              }
          }
        return result
     }
    }

使用

let mobile = "+1 (800) 444-9999"
let dictionary = ["+": "00", " ": "", "(": "", ")": "", "-": ""]
let mobileResult = mobile.replace(dictionary)
print(mobileResult) // 001800444999

基于Ramis回答的Swift 3解决方案:

extension String {
    func withReplacedCharacters(_ characters: String, by separator: String) -> String {
        let characterSet = CharacterSet(charactersIn: characters)
        return components(separatedBy: characterSet).joined(separator: separator)
    }
}

尝试根据Swift 3的命名约定，提出一个合适的函数名。

Swift 4和5已经更新了这个答案。如果你还在使用Swift 1、2或3，请查看修订历史。

你有两个选择。你可以像@jaumard建议的那样，使用replacingOccurrences()

let aString = "This is my string"
let newString = aString.replacingOccurrences(of: " ", with: "+", options: .literal, range: nil)

正如下面@cprcrack所指出的，选项和范围参数是可选的，所以如果您不想指定字符串比较选项或执行替换的范围，您只需要以下内容。

let aString = "This is my string"
let newString = aString.replacingOccurrences(of: " ", with: "+")

或者，如果数据是这样的特定格式，其中只是替换分隔符，则可以使用components()将字符串拆分为一个数组，然后可以使用join()函数将它们与指定的分隔符组合在一起。

let toArray = aString.components(separatedBy: " ")
let backToString = toArray.joined(separator: "+")

或者如果你正在寻找一个更Swifty的解决方案，不利用NSString的API，你可以使用这个。

let aString = "Some search text"

let replaced = String(aString.map {
    $0 == " " ? "+" : $0
})

下面是Swift 3的示例:

var stringToReplace = "This my string"
if let range = stringToReplace.range(of: "my") {
   stringToReplace?.replaceSubrange(range, with: "your")
} 

这在swift 4.2中很容易做到。只需使用replacingOccurrences(of: " "， with: "_")进行替换

var myStr = "This is my string"
let replaced = myStr.replacingOccurrences(of: " ", with: "_")
print(replaced)