Type NSArray cannot be downcast implicitly - ios

Question

I'm working on converting my app over to swift but I'm running into a swift error I don't quite understand yet.
In Obj-c I have a for in loop here:
for (MYVisitor *visitor in visitors) {
if (visitor.boxState == MYVisitorBoxStateChatting) {
[self.chattingVisitors addObject:visitor];
}
else {
[self.unknownVisitors addObject:visitor];
}
}
In swift I have:
for visitor: MYVisitor in visitors {
if visitor.boxState == MYVisitorBoxStateChatting {
self.chattingVisitors.addObject(visitor)
}
else {
self.unknownVisitors.addObject(visitor)
}
}
I'm getting an error in swift that says: NSArray cannot be implicitly downcast to MYVisitor, did you mean to use as to force downcast?
Xcode recommends this change: for visitor: FHVisitor in visitors as MYVisitor {...
which then gives me this error: MYVisitor does not conform to protocol SequenceType

Answer 1

If visitors is an NSArray and it is guaranteed that all its elements are of
the MYVisitor type then you can cast the array to [MYVisitor]:
for visitor in visitors as [MYVisitor] {
// ...
}
Note that this will crash at runtime if any array element is not a MYVisitor.
Alternatively, you can check the array with
if let theVisitors = visitors as? [MYVisitor] {
for visitor in theVisitors {
println(visitor.name)
}
} else {
// This is not an array of MYVisitor objects.
}
Or you can check each array element:
for item in visitors {
if let visitor = item as? MYVisitor {
// ...
} else {
// This is not a MYVisitor.
}
}