12:36 p.m.
So two separate ideas here, right? First is hiding the DataBinder
(yes!) and the second is declarative change handlers for model updates.
Both are great ideas. So +1 to both.
The only thought I had on the declarative model change handler bit was
to have an *option* to be more specific with the declaration. In other
words, I might only care about one or two properties in my model. And I
might have very different logic that I want to perform for the different
properties. So it might be nice to target a single property name when
creating the change handler. Perhaps:
@OnModelChange(propertyName="firstName")
public void onMyModelChange(@OldModel MyModel model,
@NewModel MyModel newModel,
@Source Object source)
{
// Perform name-change logic here
}
@OnModelChange(propertyName="dob")
public void onMyModelChange(@OldModel MyModel model,
@NewModel MyModel newModel,
@Source Object source)
{
// Perform date of birth change logic here
}
Alternatively it could be:
@OnModelChange(properties={"firstName", "dob"})
And then method signature could remain the same.
-Eric
On 03/11/2013 08:42 PM, Mike Brock wrote:
This gets us a little closer to something like this:
@Singleton
public class MyBean {
@Inject @AutoBound MyModel model;
@Inject @Bound Label name;
public void onMyModelChange(@NewModel MyModel updatedModel) {
// do something with updatedModel
}
@ModelSetter
public void setModel(MyModel model) {
this.model = model;
}
}
Note that I didn't inject a DataBinder<T> but rather the MyModel directly. Also
pay attention to the @ModelSetter annotation. The theory behind this is the
DataBinder<T> would be created in the Bootstrapper but never actually injected. The
@ModelSetter is a hint to create decorator code that proxies that method so the hidden
DataBinder's setModel() method can be called, and then the proxied model object then
passed on to the MyBean.setModel(). This requires AOP-style parodying of the MyBean in
this case. But I think it's a powerful tradeoff.
Mike.
On 2013-03-11, at 8:33 PM, Mike Brock <cbrock(a)redhat.com> wrote:
> While I was playing tonight I had a few ideas I wanted to bounce off everyone. What
about a higher level API for handling change events?
>
> Consider the following:
>
> ====HelloWorld.java=========================================
>
> @EntryPoint
> @Templated("#root")
> public class HelloWorld extends Composite {
> @Inject @AutoBound private DataBinder<MyModel> model;
>
> @Inject @NeedsData @Bound @DataField private TextBox name;
> @Inject @DataField private Button button;
>
> @EventHandler("button")
> private void onClick(ClickEvent e) {
> messageBox.setText("Hello there, " + model.getModel().getName());
> }
>
> @OnModelChange
> public void onMyModelChange(@OldModel MyModel model,
> @NewModel MyModel
newModel,
> @Property String propertyName,
> @Source Object
source) {
> // react to change
> }
> }
>
>
----------------------------------------------------------------------------------------------------
>
> ====ChangeEvents.java======================================
>
> @Singleton
> public class ChangeEvents [
> @OnGlobalModelChange
> public void onMyModelChange(@OldModel MyModel model,
> @NewModel MyModel
newModel,
> @Property String propertyName,
> @Source Object
source) {
> // react to change
> }
> }
>
>
----------------------------------------------------------------------------------------------------
>
> Note: the idea is that each of the specified attributes are optional with the
exception you must specify *at least* @OldModel or @NewModel. So in practice you might
just do something like this:
>
> public void onMyModelChange(@NewModel MyModel updatedModel) {
> // do something with updatedModel
> }
>
> The general idea is that the @ OnGlobalModelChange would match all *managed* (read:
injected automatically by the container such as @AutoBound) DataBinders that match
MyModel. Where-as the @OnModelChange in the HelloWorld class would be scoped just to that
one ErraiUI bean.
>
> ----
>
> This is just something I brainstormed in about 15 minutes. I am not fixed on this
particular approach. But I found myself wanting a declarative way of listening for changes
tonight that didn't involve me adding a @PostConstruct and manually adding a
PropertyChangeHandler to the DataBinder.
>
>
>
>
>
>
>
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