Xtend语法说明

Question

I'm trying to 100% understand that the following Xtend syntax means:

        myVar.addSelectionListener(
           [MultiSelectionEvent<String> event |
               println(event.toString)
           ]
        )

• myVar is a com.vaadin.ui.CheckBoxGroup class
• the addSelectionListener assume to receive a com.vaadin.event.selection.MultiSelectionListener interface

When implementing the MultiSelectionListenener , one has to implement a selectionChange method which itself takes a MultSelectionEvent object as parameter.

I understand that in my above code, I'm providing the implementation inline in my code. But could anyone provide more details about the syntax?

For example, when do we use [ ] , or | in Xtend?

Answer 1

That is Xtend's lambda syntax. So in Java you would write:

    myVar.addSelectionListener(
       (MultiSelectionEvent<String> event) -> {
           println(event.toString)
       }
    );

Xtend simply replaces (params)=>{code} with [<params>|<code>] .