我认为Regex是最灵活和可靠的方法:

var str = "This is my string"
let regex = try! NSRegularExpression(pattern: " ", options: [])
let output = regex.stringByReplacingMatchesInString(
    str,
    options: [],
    range: NSRange(location: 0, length: str.characters.count),
    withTemplate: "+"
)
// output: "This+is+my+string"

斯威夫特5.5

但这在早期版本中可能有效。

我经常替换，因为我想用_或类似的东西替换“任何空白或-”。这个对字符串的扩展让我做到了。

extension String {
    func removingCharacters(_ characters:CharacterSet) -> Self {
        Self(self.unicodeScalars.filter {
            !characters.contains($0)
        })
    }
    func removingCharacters(in string:String) -> Self {
        Self(self.unicodeScalars.filter {
            !CharacterSet(charactersIn:string).contains($0)
        })
    }
    
    func replacingCharacters(_ characters:CharacterSet, with newChar:Character) -> Self {
        String(self.compactMap( {
            CharacterSet(charactersIn: "\($0.1)").isSubset(of: characters)
             ? newChar : $0.1
        }))
    }
    
    func replacingCharacters(in string:String, with newChar:Character) -> Self {
        String(self.compactMap( {
            CharacterSet(charactersIn: "\($0)").isSubset(of: CharacterSet(charactersIn:string))
             ? newChar : $0
        }))
    }
}

用法:

print("hello \n my name\t is Joe".removingCharacters(.whitespacesAndNewlines))
print("hello \n my name\t is Joe".removingCharacters(in: " \t\n"))

print("ban annan anann ana".replacingCharacters(.whitespacesAndNewlines, with: "_"))
print("ban-annan anann ana".replacingCharacters(in: " -", with: "_"))

显然，对于单个字符，. replacingoccurrences (of: " "， with: "+")更好。

我没有做过性能比较

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

风格做在Ramis的扩展。如果有人愿意，我会很感兴趣的。

参见替换表情符号:https://stackoverflow.com/a/63416058/5946596

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)

var str = "This is my string"

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

输出是

This+is+my+string

Xcode 11•Swift 5.1

StringProtocol replacingOccurrences的突变方法可以实现如下:

extension RangeReplaceableCollection where Self: StringProtocol {
    mutating func replaceOccurrences<Target: StringProtocol, Replacement: StringProtocol>(of target: Target, with replacement: Replacement, options: String.CompareOptions = [], range searchRange: Range<String.Index>? = nil) {
        self = .init(replacingOccurrences(of: target, with: replacement, options: options, range: searchRange))
    }
}

var name = "This is my string"
name.replaceOccurrences(of: " ", with: "+")
print(name) // "This+is+my+string\n"