Swift - Array map(): transform the elements inside an array into another array

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Introduction

Swift Array map() function transforms the elements from one array into another array.

Assume you have an array that contains the prices of some items: 

let prices = [12.0,45.0,23.5,78.9,12.5]

to transform the prices array into another array with each element containing the dollar ($ ) sign, like this: 

["$12.0", "$45.0", "$23.5", "$78.9", "$12.5"]

Use the map() function:

Demo

let prices = [12.0,45.0,23.5,78.9,12.5]

var pricesIn$ = prices.map (
     {//w  w  w. ja  va  2  s . c  om
          (price:Double) -> String in
            return "$\(price)"
     }
)
print(pricesIn$)

Result

The map() function accepts a closure as its argument.

The closure itself accepts a single argument representing each element of the original array.

Here, the closure returns a String result.

The closure is called once for every element in the array.

The preceding code can be reduced to the following:

Demo

let prices = [12.0,45.0,23.5,78.9,12.5]
var pricesIn$ = prices.map(
     {// w w  w  .j a  v  a2 s  .c om
         (price) -> String in
             "$\(price)"
     }
)
print(pricesIn$)

Result

Using the shorthand argument names, and because the closure has only a single line, the code can be further reduced as follows:

Demo

let prices = [12.0,45.0,23.5,78.9,12.5]
var pricesIn$ = prices.map (
     {//w  w  w  .  j ava  2 s  .co m
         "$\($0)"
     }
)
print(pricesIn$)

Result

Related Example