How can I iterate over all items in NSMapTable in Swift

Question

I'm trying something like this in Swift but not working. Error is: Type () does not conform to type BooleanType

//visibleCollectionReusableHeaderViews is of type NSMapTable!

var enumerator: NSEnumerator = visibleCollectionReusableHeaderViews.objectEnumerator()
var myValue: AnyObject!

while (( myValue = enumerator.nextObject()))
{

}

What am I doing wrong? I don't think I understand how to iterate over an NSMapTable, or even just to get the first item in it.

Answer 1

In Swift, this is done using conditional assignment.

let enumerator = visibleCollectionReusableHeaderViews.objectEnumerator()

while let myValue: AnyObject = enumerator.nextObject() {
    println(myValue)
}

Note the non optional type for myValue. Otherwise this loop would be infinite as myValue continued to accept nil objects.

Answer 2

Or a clearer and shorter approach (Swift 3):

for key in table.keyEnumerator() {
    print(key)
}

for object in table.objectEnumerator() ?? NSEnumerator() {
    print(object)
}