Here is my Bronze Solution

[chrono1081]

Here’s what I came up with:

//MARK: - Keyboard Methods
func textField(_ textField: UITextField,
               shouldChangeCharactersIn range: NSRange,
               replacementString string: String) -> Bool {
    
    //Disallow multiple decimal places from being entered into the text field
    let existingTextHasDecimalSeparator = textField.text?.range(of: ".")
    let replacementTextHasDecimalSeparator = string.range(of: ".")
    
    //This will check to ensure only the numbers in the below character set are allowed
    let allowedCharacters = CharacterSet(charactersIn: "0123456789.")
    
    for scalar in string.unicodeScalars {
        if allowedCharacters.contains(scalar) {
            if existingTextHasDecimalSeparator != nil, replacementTextHasDecimalSeparator != nil {
                return false
            } else {
                return true
            }
        } else {
            return false
        }
    }
    return true
}