In this tiny tutorial we are going to learn how to use the map() in Swift. The map() function is used to iterate and transform elements in an array. To get a better understanding of this let’s look at some examples.

Let’s say we have an array like the one below.

var names = ["tom", "steve", "jony", "woz", "swift"]

If we wanted to capitalize each name in the array we would have to use a For Loop with the .capitalized function in swift.

var names = ["tom", "steve", "jony", "woz", "swift"]
var tempArray = [String]()

for name in names {
    tempArray.append(name.capitalized)
    names = tempArray
}

print(names)
//Output ["Tom", "Steve", "Jony", "Woz", "Swift"]

With map() we can complete the same task of capitalizing each name with less code. Below is the code we would use.

var names = ["tom", "steve", "jony", "woz", "swift"]

let capitalizedNames = names.map { (name) -> String in
    return name.capitalized
}

print(capitalizedNames)
//Output ["Tom", "Steve", "Jony", "Woz", "Swift"]

What is going on in the code above is the map() function can be used with a closure. Basically we are doing the same as the For Loop by creating a parameter called name and returning a string. Here we are returning the iterated element only capitalized just like in the previous example.

We can even break this code down further into a one liner if we wanted to like the code below.

var names = ["tom", "steve", "jony", "woz", "swift"]

let capitalizedNames = names.map { $0.capitalized }

print(capitalizedNames)
//Output ["Tom", "Steve", "Jony", "Woz", "Swift"]

This is very similar to the last example the only difference is that in the closure we use the $0 to represent the iterated item in the loop and we tell it to set it as capitalized. The $0 is a shorthand in swift programming but can be unclear and not very readable to some so I prefer the long form.

I hope this short article gives you some closure on what is map() function.

Happy programming 💻💻💻