Template model List<> items are not updated on server side when changed on client side.

[stefanuebe]

I have a simple TemplateModel with a getter and setter for a List of items. These items are displayed with a polymer dom-repeat and can be edited by vaadin-text-fields. Expectation here is, that changed made on client side are transported back to server side to be handled in an event handler.

Currently the items are unchanged. This reflects also back to direct calls of items in the handling method by @EventData("event.model.item") (or @ModelItem in short).

Java

public class TodoListDetailView extends PolymerTemplate<TodoListDetailView.Model> implements HasComponents, HasUrlParameter<Long> {
    @EventHandler
    private void handle() {
        // update repository
        System.out.println(getModel().getTodos());
    }

    public interface Model extends TemplateModel {
        @Encode(value = LongToStringEncoder.class, path = "id")
        @Encode(value = LongToStringEncoder.class, path = "list.id")
        void setTodos(List<Todo> list);

        List<Todo> getTodos();
    }
}

Polymer

<template>
        <template is="dom-repeat" items="{{todos}}">
            <vaadin-text-field on-change="handle" class="todo-name" value="{{item.name}}"></vaadin-text-field>
        </template>
</template>

Also see: #4086

[denis-anisimov]

As discussed in #4086: I don't see reasons why it doesn't work with items in the list.
The item is represented by the StateNode and any update done on the client side should be sent in the same way as for any other bean to the server side.

So I would say this is a bug (and not an enhancement) .

[heruan]

Possibly related: #3399

[Legioth]

Might also be related to #4080

[pleku]

As a workaround, you should be able to use a @ClientCallable public void update(Todo item) {...} method and pass the updated item to that one.

[denis-anisimov]

I'm able to reproduce a bug.
I have an IT test which shows it.

[denis-anisimov]

Apparently this has never be implemented.
So it's kind of may be considered as a known limitation.
We are overriding _propertiesChanged polymer element method.
This method is never called when property is updated inside an item in the list.
I will try to see what we can do here.....

[denis-anisimov]

Additional info: on the client side two way databinding works as expected for arrays.

[denis-anisimov]

_propertiesChanged is called but it's called on the dom-repeat element instead of element itself.
It causes some calls on the element itself (like _flushProperties()) but there is no info about changed item+property.