How to remove multiple spaces in Strings with Swift 2

Until Swift 2 I used this extension to remove multiple whitespaces:

func condenseWhitespace() -> String {
        let components = self.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).filter({!Swift.isEmpty($0)})
        return " ".join(components)
}

but with Swift 2 now I get the error

Cannot invoke 'isEmpty' with an argument list of type '(String)'

How could I now remove multiple spaces with Swift 2? Thnx!

In Swift 2, join has become joinWithSeparator and you call it on the array.

In filter, isEmpty should be called on the current iteration item $0.

To replace whitespaces and newline characters with unique space characters as in your question:

extension String {
    func condenseWhitespace() -> String {
        let components = self.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())
        return components.filter { !$0.isEmpty }.joinWithSeparator(" ")
    }
}

let result = "Hello  World.\nHello!".condenseWhitespace()  // "Hello World. Hello!"

Because your function does not take any parameter you could make it a property instead:

extension String {
    var condensedWhitespace: String {
        let components = self.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet())
        return components.filter { !$0.isEmpty }.joinWithSeparator(" ")
    }
}

let result = "Hello  World.\nHello!".condensedWhitespace  // "Hello World. Hello!"

---

In Swift 3 there's even more changes.

Function:

extension String {
    func condenseWhitespace() -> String {
        let components = self.components(separatedBy: NSCharacterSet.whitespacesAndNewlines)
        return components.filter { !$0.isEmpty }.joined(separator: " ")
    }
}

let result = "Hello  World.\nHello!".condenseWhitespace()

Property:

extension String {
    var condensedWhitespace: String {
        let components = self.components(separatedBy: NSCharacterSet.whitespacesAndNewlines)
        return components.filter { !$0.isEmpty }.joined(separator: " ")
    }
}

let result = "Hello  World.\nHello!".condensedWhitespace

In Swift 4.2 NSCharacterSet is now CharacterSet, and you can omit and use dot syntax:

extension String {
    func condenseWhitespace() -> String {
        let components = self.components(separatedBy: .whitespacesAndNewlines)
        return components.filter { !$0.isEmpty }.joined(separator: " ")
    }
}

let result = "Hello  World.\nHello!".condenseWhitespace()  // "Hello World. Hello!"