Swift optional binding in while loop

Question

According to 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.

The documentation only shows an example of optional-binding using if statement like:

if let constantName = someOptional {
    statements
}

I'm looking for an example of optional-binding using while loop?

Answer 1

It's the same

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

Here is a concrete example of iterating a linked list.

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