Variadic Parameters in

About Variadic Parameters

Variadic parameters in Swift allow zero or more values of the same type to be passed into a single parameter in a function. This is indicated by appending ... to the type annotation of the parameter.

These values will be automatically grouped into an array with elements of the same type as the type of the variadic parameter.

func geometricMean(_ numbers: Double...) -> Double {
  var total = 1.0
  for number in numbers {
      total *= number
  }
  return pow(total, 1.0 / Double(numbers.count))
}

geometricMean(1, 2, 3, 4, 5)
// => 2.605171084697352

When using variadic parameters, Swift has two limitations:

1. Swift only allows functions to have one variadic parameter. It has been decided that this restriction will be removed in a future release of Swift, but it is currently still in place.
2. If a function has parameters that follow the variadic parameter in the definition, the first parameter following the variadic parameter is required to have an argument label.