`Ambiguous reference to member` when creating convenience init in extension

Question

This is my init:

extension NSNumberFormatter {

    convenience init(digits: Int = 0) {
        self.init() //ambiguous reference to member 'NSNumberFormatter.init'

        groupingSeparator = " "
        decimalSeparator = "."
        numberStyle = .DecimalStyle
        roundingMode = .RoundHalfDown

        maximumFractionDigits = digits
        minimumFractionDigits = digits
    }
}

What is the reason?

The same problem is when I put self.init() at the end of my convenience initializer.

Answer 1

The reason is that you have created a new init that can be called without any parameters since digits has a default value of 0. So now, init() can refer to the default initializer or your new one. If you remove the default value for digits, it will then compile.