How to remove special characters from string in Swift 2?

The answer in How to strip special characters out of string? is not working.

Here is what I got and it gives me an error

func removeSpecialCharsFromString(str: String) -> String {
    let chars: Set<String> = Set(arrayLiteral: "abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLKMNOPQRSTUVWXYZ1234567890+-*=(),.:!_")

    return String(str.characters.filter { chars.contains($0) }) //error here at $0
}

The error at $0 says _Element(aka Character) cannot be converted to expected argument type 'String'.