修改现有可变字符串的类别:

extension String
{
    mutating func replace(originalString:String, withString newString:String)
    {
        let replacedString = self.stringByReplacingOccurrencesOfString(originalString, withString: newString, options: nil, range: nil)
        self = replacedString
    }
}

使用:

name.replace(" ", withString: "+")

你可以用这个:

let s = "This is my string"
let modified = s.replace(" ", withString:"+")    

如果你在你的代码中添加这个扩展方法:

extension String
{
    func replace(target: String, withString: String) -> String
    {
       return self.stringByReplacingOccurrencesOfString(target, withString: withString, options: NSStringCompareOptions.LiteralSearch, range: nil)
    }
}

斯威夫特3:

extension String
{
    func replace(target: String, withString: String) -> String
    {
        return self.replacingOccurrences(of: target, with: withString, options: NSString.CompareOptions.literal, range: nil)
    }
}

var str = "This is my string"
str = str.replacingOccurrences(of: " ", with: "+")
print(str)

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
})

你可以测试这个:

let newString = test。stringByReplacingOccurrencesOfString(" "， withString: "+"，选项:nil，范围:nil)

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