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A while loop statement in Swift programming language repeatedly executes a designated statement as long as a given condition remains true. The condition is very crucial in the while loop it prevents the loop from becoming an infinite loop. So always check the condition in the while loop.
The key point of a while loop is that the loop might not ever run. When the condition is tested and the result is false, the loop body will be skipped and the first statement after the while loop will be executed.
Syntax
The syntax of a while loop −
while condition { statement(s) }
Here statement(s) may be a single statement or a block of statements. The condition may be any expression. The loop iterates while the condition is true. When the condition becomes false, the program control passes to the line immediately following the loop.
Flow Diagram
The following flow diagram will show how the while loop works −
Example
The following Swift program uses the comparison operator < to compare the value of the variable index against 20. While the value of the index is less than 20, the while loop continues executing a block of code next to it and as soon as the value of the index becomes equal to 20, it comes out.
import Foundation var index = 10 // Here the loop continues executing until the index is less than 20 while index < 20 { print( "Value of index is (index)") index = index + 1 }
Output
It will produce the following output −
When executed, the above code produces the following result −
Value of index is 10 Value of index is 11 Value of index is 12 Value of index is 13 Value of index is 14 Value of index is 15 Value of index is 16 Value of index is 17 Value of index is 18 Value of index is 19
Example
Swift program to find the sum using a while loop.
import Foundation var sum = 0 var num = 1 // Here the loop continues executing until num is less than equal to 9 while num <= 9 { sum += num num += 1 } print("Sum of numbers from 1 to 9 is: (sum)")
Output
It will produce the following output −
When executed, the above code produces the following result −
Sum of numbers from 1 to 9 is: 45
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