On 6/10/11 1:18 , Frank Grimm wrote:
The @Ignore comment on org.qi4j.runtime.property.PropertyTest ("This is
an incorrect satisfiedBy case. [...]") seems to indicate that
SideEffects on Properties might not work right now.?
If this is the case, is there another Qi4j-ish way to get notified about
property value changes? I'm intending to update UI elements whenever the
underlying Composites change state.
Right, we don't support this directly in Qi4j right now, and I agree
that there are perfectly valid cases where one would want to do what
you're asking for, at least for transient composites (values and
entities, not so much).
The only workarounds I can think of for now are these:
1) When a Property is set constraints are checked first, so you could
implement a Constraint that always passes, but which delegates the new
value to whatever mechanism you use to detect changes
2) Implement a Concern for Property<> methods that wrap the Property
with something that propagates the get/set calls accordingly. Something
like:
@AppliesTo( { PropertyMixin.PropertyFilter.class } )
public class PropertyNotificationConcern
extends GenericConcern
{
public Object invoke( Object proxy, Method method, Object[] args )
throws Throwable
{
final Property property = (Property)next.invoke(proxy,method,args);
return new ComputedPropertyInstance<Object>(property)
{
public Object get()
{
// Notify here
return property.get();
}
public void set(Object object)
{
property.set(object);
// Notify here
}
}
}
}
---
Something like that should work reasonably well. You could either send
events to an event bus in your app, or have interested parties register
themselves in the metaInfo() of the property.
/Rickard
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