Regex in Swift gives different result

Question

I am using this regex in my Swift,

    let regex = try! NSRegularExpression(pattern: "^[a-zA-Zåçêëèïîìæôöòûùÿáíóúñ]+(?:[-\' ][a-zA-Zåçêëèïîìæôöòûùÿáíóúñ]