How to create an FBOpenGraphAction in Swift?

With objective-c an FBOpenGraphAction is created like:

id<FBOpenGraphAction> action = (id<FBOpenGraphAction>)[FBGraphObject graphObject];

What is the equivalent in Swift?

I would have assumed it is something like this:

let action = FBGraphObject.graphObject() as FBOpenGraphAction

But this causes a signal at runtime.

See also FBOpenGraphAction runtime error in Swift

Any ideas are very appreciated.