Tuple in Swift

This article explains what a Tuple is and when and where it is used. Happy reading!!!

Image for post
Image for post
pic credit: Stocksnap.io

Tuple is a group of different values represented as one . According to apple, a tuple type is a comma-separated list of zero or more types, enclosed in parentheses. It’s a miniature version of a struct.

Let’s consider an example: A name say John smith can be declared as a tuple like ("John", "Smith") . It holds the first and last name of a person. You can access the inner values using the dot(.) notation followed by the index of the value:

var person = ("John", "Smith")

var firstName = person.0 // John
var lastName = person.1 // Smith

The type of a tuple is determined by the values it has. So ("tuple", 1, true) will be of type (String, Int, Bool).

() is the empty tuple – it has no elements. It also represents the Void type.

Tuples don’t conform to the hashable protocol. Hence it cannot be used as dictionary keys.

You can declare a tuple like any other variable or constant. To initialize it you will need a another tuple or a tuple literal. A tuple literal is a list of values separated by commas between a pair of parentheses. You can use the dot notation to change the values from a tuple if it’s declared as a variable.

var point = (0, 0)

point.0 = 10
point.1 = 15

point // (10, 15)

Note: Tuple are value types. When you initialize a variable tuple with another one it will actually create a copy.

var origin = (x: 0, y: 0)

var point = origin
point.x = 3
point.y = 5

print(origin) // (0, 0)
print(point) // (3, 5)

You can name the elements from a tuple and use those names to refer to them. An element name is an identifier followed by a colon(:).

var person = (firstName: "John", lastName: "Smith")var firstName = person.firstName // John
var lastName = person.lastName // Smith

You can use tuples to initialize more than one variable on a single line:

var (a, b, c) = (1, 2, 3)

You can return multiple values from a function if you set the result type to a tuple.

Please note that tuples are passed by value, not reference.

Image for post
Image for post

In the above code, for code readability, I’ve used a typealias to pre-define the tuple’s structure.

for (key,value) in myDictionary {  println("My key is \(key) and it has a value of \(value)")}

In the above iteration through dictionary example, if we need only the key , then you can use “_” to ignore the value for key.

Note: the _ means “I don’t care about that value”

for (key,_) in myDictionary {println("My key is \(key)")

let http404Error = (404, "Not Found")
// http404Error is of type (Int, String), and equals (404, "Not Found")

You can decompose a tuple’s contents into separate constants or variables, which you then access as usual:

let (statusCode, statusMessage) = http404Errorprint("The status code is \(statusCode)")// Prints "The status code is 404"print("The status message is \(statusMessage)")// Prints "The status message is Not Found"

If you only need some of the tuple’s values, ignore parts of the tuple with an underscore (_) when you decompose the tuple:

let (justTheStatusCode, _) = http404Errorprint("The status code is \(justTheStatusCode)")// Prints "The status code is 404"

Alternatively, access the individual element values in a tuple using index numbers starting at zero:

print("The status code is \(http404Error.0)")// Prints "The status code is 404"print("The status message is \(http404Error.1)")// Prints "The status message is Not Found"

You can name the individual elements in a tuple when the tuple is defined:

let http200Status = (statusCode: 200, description: "OK")

we’re gonna mix it up by creating tuple which contains another tuple.

let bar: (Int, (Bool, String)) = (1, (false, "Hello"))print(bar.0) // print: “1”print(bar.1.0) // print: “false”print(bar.1.1) // print: “Hello”
var a = 5 
var b = 4
(b, a) = (a, b)

The best place to use a tuple would be when you want a function that can return multiple types. If you’re an Objective-C developer, this concept sounds impossible unless you use an array or dictionary. Previously we’ve had to overcome such problem by either return an NSArray or NSDictionary.

Sources: Medium article, Weheartswift.


If you enjoyed reading this post, please share and give some clapps so others can find it 👏👏👏👏👏 !!!!

You can follow me on Medium for fresh articles. Also, connect with me on LinkedIn.

If you have any comment, question, or recommendation, feel free to post them in the comment section below!

Written by

iOS and tvOS developer, dreamer, photographer 🤨

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store