View Properties and Array Filters
Another very useful feature of view properties is that you can use them within array filter callbacks for your scenario observers.
So you can prevent the browser from having to download unnecessary elements of your arrays.
To expand on the previous example; instead of fetching the entire array you could instead instruct the scenario observer to filter the array by the selected value.
// Array filter using a view property
view.withFirstScenario()
.withViewProperties('selectedCountry')
.withEntities('Population')
.filter('Population', function(viewProperties) {
var country = viewProperties.get('selectedCountry');
return {'Country': [country]};
})
.notify(function(scenario, viewProperties) {
var populations = scenario.getArray('Population');
var country = viewProperties.get('selectedCountry');
// This will get the population for the selected country
var population = populations.getValue([country]);
})
.start();
You can see from the above example that a view properties accessor is passed into the filter callback as the first argument. This is again an instance of MaskedViewProperties and only allows access to view properties that are being observed by the scenario observer.