swap Example (Swap Variables)Use the built-in swap method to exchange the value of two variables. Use swap with different types.
This page was last reviewed on Jan 13, 2024.
Swap. Sometimes it is necessary to exchange the values within 2 variables—this may be useful within certain loops. In Swift 5.9, we can use the built-in swap() function.
Syntax note. Swap receives references (inout) to 2 variables—if we do not provide the reference operator we will receive a compile-time error.
Example. This Swift 5.9 program uses the built-in swap() 2 times, on different variable types. Please note that the variables were declared with the "var" keyword.
Step 1 We declare and initialize 2 strings, using the "var" keyword to allow the strings to be reassigned.
Step 2 We pass the strings as references to the swap method. This changes the values the strings are assigned to.
Step 3 The swap() function can be used on any 2 variables of the same type—here we use Ints.
Step 4 Again, the two variables now have the opposite value. No complicated if-statements were needed.
// Step 1: declare 2 Strings. var left = "left" var right = "right" // Step 2: swap the Strings and print them. swap(&left, &right) print(left, right) // Step 3: declare two Ints. var zero = 0 var one = 1 // Step 4: swap the Ints and print the swapped values. swap(&zero, &one) print(zero, one)
right left 1 0
Inout error. If we do use an ampersand when passing a variable, we will get a "passing value" error. This can be easily corrected with a single character.
programs\program.swift:9:6: error: passing value of type 'String' to an inout parameter requires explicit '&'
Summary. With the useful swap() function, built into the Swift standard library, we can swap variables. This function sometimes allows to eliminate a cumbersome if-statement.
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Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Jan 13, 2024 (new).
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