Variable Arguments

Varargs i.e. variable function arguments are a very useful technique for situations where the number of function parameters is unknown.

// classic example

func sum(of numbers: Int...) -> Int {

     // add up all numbers with the + operator

     return numbers.reduce(0, +)

}



let theSum = sum(of: 1, 2, 5, 7, 9) // 24

A tuple can be useful here if your requirement goes beyond simple integers. Take this function, which does a batch update of n entities in a database:

func batchUpdate(updates: (String, Int)...) {

     self.db.begin()

     for (key, value) in updates {

         self.db.set(key, value)

     }

     self.db.end()

}



batchUpdate(updates: (\"tk1\", 5), 

        (\"tk7\", 9), 

        (\"tk21\", 44), 

        (\"tk88\", 12))

This pattern allows us to model the insertions in a very simple manner without having to introduce additional struct types.