Split a String into an Array in Swift?

Just call componentsSeparatedByString method on your fullName

import Foundation

var fullName: String = "First Last"
let fullNameArr = fullName.componentsSeparatedByString(" ")

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

Update for Swift 3+

import Foundation

let fullName    = "First Last"
let fullNameArr = fullName.components(separatedBy: " ")

let name    = fullNameArr[0]
let surname = fullNameArr[1]

The easiest method to do this is by using componentsSeparatedBy:

For Swift 2:

import Foundation
let fullName : String = "First Last";
let fullNameArr : [String] = fullName.componentsSeparatedByString(" ")

// And then to access the individual words:

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

For Swift 3:

import Foundation

let fullName : String = "First Last"
let fullNameArr : [String] = fullName.components(separatedBy: " ")

// And then to access the individual words:

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

Swift Dev. 4.0 (May 24, 2017)

A new function split in Swift 4 (Beta).

import Foundation
let sayHello = "Hello Swift 4 2017";
let result = sayHello.split(separator: " ")
print(result)

Output:

["Hello", "Swift", "4", "2017"]

Accessing values:

print(result[0]) // Hello
print(result[1]) // Swift
print(result[2]) // 4
print(result[3]) // 2017

Xcode 8.1 / Swift 3.0.1

Here is the way multiple delimiters with array.

import Foundation
let mathString: String = "12-37*2/5"
let numbers = mathString.components(separatedBy: ["-", "*", "/"])
print(numbers)

Output:

["12", "37", "2", "5"]

Swift 4 or later

If you just need to properly format a person name, you can use PersonNameComponentsFormatter.

The PersonNameComponentsFormatter class provides localized representations of the components of a person’s name, as represented by a PersonNameComponents object. Use this class to create localized names when displaying person name information to the user.

// iOS (9.0 and later), macOS (10.11 and later), tvOS (9.0 and later), watchOS (2.0 and later)
let nameFormatter = PersonNameComponentsFormatter()

let name =  "Mr. Steven Paul Jobs Jr."
// personNameComponents requires iOS (10.0 and later)
if let nameComps  = nameFormatter.personNameComponents(from: name) {
    nameComps.namePrefix   // Mr.
    nameComps.givenName    // Steven
    nameComps.middleName   // Paul
    nameComps.familyName   // Jobs
    nameComps.nameSuffix   // Jr.

    // It can also be configured to format your names
    // Default (same as medium), short, long or abbreviated

    nameFormatter.style = .default
    nameFormatter.string(from: nameComps)   // "Steven Jobs"

    nameFormatter.style = .short
    nameFormatter.string(from: nameComps)   // "Steven"

    nameFormatter.style = .long
    nameFormatter.string(from: nameComps)   // "Mr. Steven Paul Jobs jr."

    nameFormatter.style = .abbreviated
    nameFormatter.string(from: nameComps)   // SJ

    // It can also be use to return an attributed string using annotatedString method
    nameFormatter.style = .long
    nameFormatter.annotatedString(from: nameComps)   // "Mr. Steven Paul Jobs jr."
}

edit/update:

Swift 5 or later

For just splitting a string by non letter characters we can use the new Character property isLetter:

let fullName = "First Last"

let components = fullName.split{ !$0.isLetter }
print(components)  // "["First", "Last"]\n"

Update for Swift 5.2 and the simpliest way

let paragraph = "Bob hit a ball, the hit BALL flew far after it was hit. Hello! Hie, How r u?"

let words = paragraph.components(separatedBy: [",", " ", "!",".","?"])

This prints,

["Bob", "hit", "a", "ball", "", "the", "hit", "BALL", "flew", "far", "after", "it", "was", "hit", "", "Hello", "", "Hie", "", "How", "r", "u", ""]

However, if you want to filter out empty string,

let words = paragraph.components(separatedBy: [",", " ", "!",".","?"]).filter({!$0.isEmpty})

Output,

["Bob", "hit", "a", "ball", "the", "hit", "BALL", "flew", "far", "after", "it", "was", "hit", "Hello", "Hie", "How", "r", "u"]

But make sure, Foundation is imported.

As an alternative to WMios's answer, you can also use componentsSeparatedByCharactersInSet, which can be handy in the case you have more separators (blank space, comma, etc.).

With your specific input:

let separators = NSCharacterSet(charactersInString: " ")
var fullName: String = "First Last";
var words = fullName.componentsSeparatedByCharactersInSet(separators)

// words contains ["First", "Last"]

Using multiple separators:

let separators = NSCharacterSet(charactersInString: " ,")
var fullName: String = "Last, First Middle";
var words = fullName.componentsSeparatedByCharactersInSet(separators)

// words contains ["Last", "First", "Middle"]

Swift 4

let words = "these words will be elements in an array".components(separatedBy: " ")

The whitespace issue

Generally, people reinvent this problem and bad solutions over and over. Is this a space? " " and what about "\n", "\t" or some unicode whitespace character that you've never seen, in no small part because it is invisible. While you can get away with

A weak solution

import Foundation
let pieces = "Mary had little lamb".componentsSeparatedByString(" ")

If you ever need to shake your grip on reality watch a WWDC video on strings or dates. In short, it is almost always better to allow Apple to solve this kind of mundane task.