Split a String into an array in Swift?

Say I have a string here:

var fullName: String = "First Last"

I want to split the string base on white space and assign the values to their respective variables

var fullNameArr = // something like: fullName.explode(" ") 

var firstName: String = fullNameArr[0]
var lastName: String? = fullnameArr[1]

Also, sometimes users might not have a last name.