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Swift Tuple ExamplesUse tuples to combine values together. Tuples can be returned from funcs.
Tuples. In Swift programs, tuples can combine related data. When looping over a dictionary, we access the data as tuples. To return multiple values in a method, we return a tuple.
Tuple syntax. The syntax for tuples in Swift is simple and concise. We just specify the values we want to be a part of the tuple, in parentheses.
First example. Here we create a tuple with a String and an Int. We access the first item in the tuple with the expression entry.0. And the second item is at index 1.
Note To create a tuple, we use a comma-separated list of the values in parentheses.
Further A tuple can contain more than two elements. But be careful with large tuples—an array may be a better option.
// Create a tuple with two items. let entry = ("cat", 100) // Access item 0 and item 1. let name = entry.0 let number = entry.1 // Display name, number and entire tuple. print(name) print(number) print(entry)
cat 100 (cat, 100)
Decompose. A tuple is a "composition" of multiple values. So when we decompose a tuple, we break it apart (unpack it) into its smallest parts.
Underscore This is a special variable name in Swift. It indicates a variable we will not need to access.
let color = ("Green", 822, 0) // Decompose the tuple to unpack its items into variables. // ... An underscore means no variable. let (name, code, _) = color print(name) print(code)
Green 822
Named tuple. Indexes are fine for some tuples. But for more complex ones, we can provide names for the items in a tuple upon creation. We can then reference those names.
// Use named items in tuple. let language = (name: "Ruby", speed: 0, usability: 10) // Access named items in tuple. print("\(language.name) has speed of \(language.speed)") print("\(language.name) has usability of \(language.usability)")
Ruby has speed of 0 Ruby has usability of 10
Multiple return values. To return many values at once, a method can return a tuple. Here we return two Ints from a func. No inout parameters are needed.
func computeData(x: Int) -> (Int, Int) { // This func returns a tuple. return (x * 2, x * 100) } // Get tuple from method. let result = computeData(3) print(result)
(6, 300)
Switch. A tuple can be switched upon. We specify all the elements in each case in the switch statement. Here is the simplest syntax form.
Switch
Tip Each case in a tuple switch must have the correct "tuple pattern" with a matching number of elements.
let value = ("bird", 100) // Switch on the tuple. switch (value) { case ("bird", 100): print("Bird 100") default: print("Unknown") }
Bird 100
Let, switch. This example uses the "let" keyword to capture a value in a tuple switch. The "let animal" value is the first item in a tuple. The second item must be 100 to match.
let value = ("elephant", 100) // Use let to capture a variable in a tuple. switch (value) { case (let animal, 100): print("\(animal) has value 100") default: print("Default") }
elephant has value 100
Switch, underscore. This is another tuple switch feature. We can use the underscore to match any value in a tuple's item. We switch on the third item in a tuple in this example.
let elements = ("aa", "bb", 2) // Match complete tuple values. switch (elements) { case (_, _, 1): print("Third value is 1") case (_, _, 2): print("Third value is 2") default: print("Error") }
Third value is 2
A review. Tuples are a core part of the Swift language. They are used throughout code. They reduce complexity by composing multiple items into one.
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