Camel-case a string in Swift

camel_case.swift

func camelCaseString(source: String) -> String {
    if contains(source, " ") {
        let first = source.substringToIndex(advance(source.startIndex, 1))
        let cammel = NSString(format: "%@", (source as NSString).capitalizedString.stringByReplacingOccurrencesOfString(" ", withString: "", options: nil, range: nil)) as String
        let rest = dropFirst(cammel)
        return "\(first)\(rest)"
    } else {
        let first = (source as NSString).lowercaseString.substringToIndex(advance(source.startIndex, 1))
        let rest = dropFirst(source)
        return "\(first)\(rest)"
    }
}

camelCaseString("os version")
camelCaseString("HelloWorld")
camelCaseString("someword With Characters")

camel_cased_string_extension.swift

extension String {
    var camelCasedString: String {
        let source = self
        if contains(source, " ") {
            let first = source.substringToIndex(advance(source.startIndex, 1))
            let cammel = NSString(format: "%@", (source as NSString).capitalizedString.stringByReplacingOccurrencesOfString(" ", withString: "", options: nil, range: nil)) as String
            let rest = dropFirst(cammel)
            return "\(first)\(rest)"
        } else {
            let first = (source as NSString).lowercaseString.substringToIndex(advance(source.startIndex, 1))
            let rest = dropFirst(source)
            return "\(first)\(rest)"
        }
    }
}

"os version".camelCasedString
"HelloWorld".camelCasedString
"someword With Characters".camelCasedString