Swift While和Repeat While循環

當迭代次數未知時，While和Repeat while循環被用作for-in循環的替代方案。愛掏網 - it200.comWhile循環執行一組語句，直到條件為假為止。愛掏網 - it200.com這種循環通常在你不知道迭代次數時使用。愛掏網 - it200.com

在Swift中有兩種類型的循環：

1. While循環
2. Repeat While循環

Swift的While循環在每次執行時都會評估其條件。愛掏網 - it200.com

語法

while (TestExpression) {
    // statements
}

在這里，TestExpression是一個布爾表達式。愛掏網 - it200.com如果它為真，則執行while循環中的語句。愛掏網 - it200.com

• 在while循環中，語句將被執行。愛掏網 - it200.com
• 然后，TestExpression將再次進行評估。愛掏網 - it200.com

這個過程會一直進行，直到TestExpression為假為止。愛掏網 - it200.com當TestExpression得到假條件時，while循環終止。愛掏網 - it200.com

While循環的流程圖

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 ")

輸出：

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循環執行直到條件被評估為false，并且一旦獲得false條件，它就終止。愛掏網 - it200.com