Errai databinding - nested binding

[slavap]

I'm not sure how properly formulate my question, perhaps example is the best way to do that:

@Bindable

class MyNestedEntity {

    String getA();

    void setA(String value);

    String getB();

    void setB(String value);

}

@Bindable

class MyModel {

    MyNestedEntity getData();

    void setData(MyNestedEntity value);

}

UI is bound to model as "data.a" and "data.b"

And now let's say I'm trying to change data property to another entity, like this:

MyNestedEntity newEntity = new MyNestedEntity();

model.setData(newEntity);

UI is not updated. To make it working, I have to add additional method to my model:

void setNewData(MyNestedEntity value) { this.data = value; }

and use model.setNewData(newEntity) when I want to replace nested data.

Not a big deal, but the question is - why? It looks kind of strange and additional code is not actually needed.

The root of this behavior is lying in BindableProxyAgent.updateWidgetsAndFireEvents() implementation.

nestedBinder.setModel() is called only in case of parameterless method, but for some reason is not called by updateWidgetsAndFireEvent(String property, P oldValue, P newValue);

Is there any reason for for such design? Or it's just a bug?

If nestedBinder.setModel() logic is added to second method, then setNewData(...) won't be needed anymore in my model, and code will be more straightforward.

[ddadlani]

Hello Slava,

I am not entirely sure as to how you are trying to use the databinding feature. Are you using a databinder anywhere in your code?
Is there a code sample you could show us to help illustrate your usage?

Regards,
Divya

[slavap]

I've already shown example in my previous post. What exactly is not clear?

[ddadlani]

Hello,

I have written a test case to try and reproduce your example. Is this the data binding behaviour you are referring to?
New test case for data binding to check for nested model change · ee72953 · divd/errai · GitHub

As I understand your question, you want newChild.value and textBox in the test case to be automatically synchronized. Is this correct?

Divya.

[slavap]

Hi,

Thanks for answer! Your code looks very close to mine, but there is a slight difference, and for some reason it's not working in my case.

Your test should be looking like this:

TextBox textBox = new TextBox();

TestModel model = new TestModel();

DataBinder<TestModel> dataBinder = DataBinder.forModel(model, InitialState.FROM_MODEL);

model = dataBinder.bind(textBox, "child.value").getModel();

textBox.setValue("old string", true);

assertEquals("Model not properly updated", "old string", model.getChild().getValue());

TestModel newChild = new TestModel();

newChild.value = "new string"; // populate values before assignment

model.setChild(newChild);

assertEquals("Widget not properly updated", "new string", textBox.getText());

[ddadlani]

Hello Slava,

The test case as you have described it, with the value change before assignment, passes. See Edited test case for databinding after model change and update. Test cas... · 9a73041 · divd/errai · GitHub
The previous test case that I sent you, however, does not. I have created a bug report for this at [ERRAI-792] Widget not updated if databinder is bound to a new model and the new model's value is changed. - JBoss Issue…

What version of Errai are you using?

Regards,

Divya

[slavap]

Hello,

I'm using 3.0.2

Really really strange, let me check my code one more time.

Anyway, leave in your test case BOTH versions of this functionality, because your code was proper test as well.