Wildcard Pattern

The wildcard pattern ignores the value to be matched against. In this case any value is possible. This is the same pattern as let _ = fn() where the _ indicates that you don't wish to further use this value. The interesting part is that this matches all values including nil.

You can also match optionals by appending a ? to make it _?:

let p: String? = nil

switch p {

// Any value is possible, but only if the optional has a value

case _?: print (\"Has String\")

// Only match the empty optional case

case nil: print (\"No String\")

}

As you've seen in the trading example, it also allows you to omit the data you don't need from matching enums or tuples:

switch (15, \"example\", 3.14) {

// We're only interested in the last value

case (_, _, let pi): print (\"pi: \(pi)\")

}