9.19. Swift While cycle

9.19.1. Grammar #

Swift while the syntax format of the loop is as follows:

while condition { statement(s) } 

In grammar statement(s) can be a statement or a block of statements. condition can be an expression. If the condition is true``will run a series of statements repeatedly until the condition changes to ``false .

The number 0, the strings '0' and '' , empty list() and undefined variables are false and the rest are true . true use it backwards! Number or not , take the reverse and return false .

Flow chart:

9.19.2. Example #

import Cocoa var index = 10 while index < 20 { print( "The value of index is \(index)") index = index + 1 } 

The output of the above program execution is as follows:

The value of index is 10 The value of index is 11 The value of index is 12 The value of index is 13 The value of index is 14 The value of index is 15 The value of index is 16 The value of index is 17 The value of index is 18 The value of index is 19