Question

I’m trying to load a bunch of com.mongodb.DBObject objects in to a Vaadin BeanItemContainer to display in a table. I’m getting stuck on the translation of the constructor from Java to Scala.

The constructor definition is:

BeanItemContainer(Class<? extends BT> type) 

This passes the scala compiler:

val bic = new BeanItemContainer(Class.forName("com.mongodb.DBObject"))

However, when I try to add an item:

mtl.toArray.foreach {t => bic.addBean(t)}

I get the following error:

[ERROR]com/sentientswarm/traderdashboard/UploadTradesWindow.scala:140: error: type mismatch;
 found   : t.type (with underlying type com.mongodb.DBObject)
 required: ?0 where type ?0
            mtl.toArray.foreach {t => bic.addBean(t)}

Any thoughts/suggestions?

UPDATE:
Tried:

val bic: BeanItemContainer[DBObject] = new BeanItemContainer(Class.forName("com.mongodb.DBObject"))

Result:

[ERROR]com/sentientswarm/traderdashboard/UploadTradesWindow.scala:140: error: type mismatch;
 found   : java.lang.Class[?0(in value bic)] where type ?0(in value bic)
 required: java.lang.Class[_ <: com.mongodb.DBObject]
            val bic: BeanItemContainer[DBObject] = new BeanItemContainer(Class.forName("com.mongodb.DBObject"))
                                                                                      ^

Thanks,
John

Answer 1

Any reason you’re using Class.forName? I don’t think the compiler can infer the type from the returned object from that call, it would just be Class[_]. If you use classOf, it should let the compiler determine the type:

val bic = new BeanItemContainer[DBObject](classOf[DBObject]))

In other words: DBObject.class in Java translates to classOf[DBObject] in Scala.