Swift While和Repeat While循环

当迭代次数未知时，While和Repeat while循环被用作for-in循环的替代方案。While循环执行一组语句，直到条件为假为止。这种循环通常在你不知道迭代次数时使用。

在Swift中有两种类型的循环：

1. While循环
2. Repeat While循环

Swift While循环

Swift的While循环在每次执行时都会评估其条件。

语法

while (TestExpression) {
    // statements
}

在这里，TestExpression是一个布尔表达式。如果它为真，则执行while循环中的语句。

• 在while循环中，语句将被执行。
• 然后，TestExpression将再次进行评估。

这个过程会一直进行，直到TestExpression为假为止。当TestExpression得到假条件时，while循环终止。

While循环的流程图

示例

var currentLevel:Int = 0, finalLevel:Int = 6
let gameCompleted = true
while (currentLevel <= finalLevel) {
    //play game
    if gameCompleted {
        print("You have successfully completed level \(currentLevel)")
        currentLevel += 1
    }
}
//outside of while loop
print("Terminated! You are out of the game ")

输出：

You have successfully completed level 0
You have successfully completed level 1
You have successfully completed level 2
You have successfully completed level 3
You have successfully completed level 4
You have successfully completed level 5
You have successfully completed level 6
Terminated! You are out of the game 

在上面的程序中，while循环执行直到条件被评估为false，并且一旦获得false条件，它就终止。