Default Parameter Values
Swift supports default parameters unlike in Objective-C where there is no concept of default parameter values. The following is an example of a function that adds punctuation to a sentence, where you declare a period to be the default punctuation:
func addPunctuation(#sentence: String, punctuation: String = ".") -> String { return sentence + punctuation}
If a parameter is declared with a default value, it will be made into an external parameter. If you’d like to override this functionality and not include an external parameter, you can insert an underscore (_) as your external variable. If you wanted a version of addPunctuation that had no external parameters, its declaration would look ...
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