A Swift extension to split a string into an array of strings

dub.swift

extension String {
    func split(string: String) -> [String] {
        guard !string.characters.isEmpty else { return [string] }
        
        var strings: [String] = []
       
        let targetDistance = string.characters.startIndex.distanceTo(string.characters.endIndex)

        var currentIndex = self.startIndex
        var currentView = String.CharacterView()

        while currentIndex < self.endIndex {
            let tmpEndIndex = currentIndex.advancedBy(targetDistance, limit: self.endIndex)

            if string == String(self[currentIndex..<tmpEndIndex]) {
                if !currentView.isEmpty {
                    strings += [String(currentView)]
                }
                
                currentView = String.CharacterView()
                currentIndex = currentIndex.advancedBy(targetDistance)
            } else {
                currentView.append(self[currentIndex])
                currentIndex = currentIndex.advancedBy(1)
            }
        }
        
        if !currentView.isEmpty {
            strings += [String(currentView)]
        }
        
        return strings
    }
}

let source = "WUBWEWUBAREWUBWUBTHEWUBCHAMPIONSWUBMYWUBFRIENDWUB"
let answer = source.split("WUB").joinWithSeparator(" ") // "WE ARE THE CHAMPIONS MY FRIEND"