while 循环中的 Swift 可选绑定(bind)

Question

根据 Swift documentation :

Optional binding can be used with if and while statements to check for a value inside an optional, and to extract that value into a constant or variable, as part of a single action.

文档仅显示了使用 if 语句的可选绑定(bind)示例:

if let constantName = someOptional {
    statements
}

我正在寻找使用 while 循环的可选绑定(bind)示例？

Answer 1

是一样的

while let someValue = someOptional
{
    doSomethingThatmightAffectSomeOptional(with: someValue)
}

下面是一个迭代链表的具体例子。

class ListNode
{
    var value: String
    var next: ListNode?

    init(_ value: String, _ tail: ListNode?)
    {
        self.value = value
        self.next = tail
    }
}

let list = ListNode("foo", ListNode("bar", nil))

var currentNode: ListNode? = list
while let thisNode = currentNode
{
    print(thisNode.value)
    currentNode = thisNode.next
}

// prints foo and then bar and then stops