CODEWITHSUNDEEP
swift
Joe WIllsher
Joe WIllsher

Reputation: 39

How does the Swift runtime handle tuples?

I've been trying to swap 2 objects without using a temp value, which be done like so:

var a = "Hello, "
var b = "world!"

(a,b) = (b,a)

a    // "world!"
b    // "Hello, "

Does anyone know how the language is doing this, is the second tuple (b,a) stored in memory to allow the first one to reassign itself, or does it do it all by switching references?

Thanks in advance

Upvotes: 2

Views: 293

Answers (1)

akashivskyy
akashivskyy

Reputation: 45210

This kind of "switching" does the following:

  • Replaces the pointers for class types

    var classA = NSString(string: "foo")
var classB = NSString(string: "bar")

NSLog("%p %p", classA, classB) // 0x7fecd351def0 0x7fecd341cc30
(classA, classB) = (classB, classA)
NSLog("%p %p", classA, classB) // 0x7fecd341cc30 0x7fecd351def0

  • Creates new values (copies) for value types

    var valueA = "baz"
var valueB = "qux"

NSLog("%p %p", valueA, valueB) // 0x7fecd34201b0 0x7fecd34211e0
(valueA, valueB) = (valueB, valueA)
NSLog("%p %p", valueA, valueB) // 0x7fecd351c880 0x7fecd351de90

Upvotes: 1

Related Questions