chaining observables with Rx

eventStream.js

// watch angular scope $destroy expression and create a kill observable
var controllerScopeIsDestroyed = angularObservableSvc.watchToObservable($scope, '$destroy');

// get datamart status request
var statusObs = dataMartSvc.getSavedState({
    userId: $stateParams.id,
    refId: $stateParams.ref
});

// get custom views request
var getCustomViewsObs = dataMartSvc.getCustomViews();

// generic service
var service = {

    // status = statusObs, views = getCustomViewsObs
    setupDMwithCustomViews(status, views) {
        var customViews = utilities.mapCdaResponse(views.data);
        var viewsCollection = customViews ? [customViews] : [];
        var dataMart = _.extend(status, {customViews: viewsCollection});

        return dataMart;
    }
}

/*
 * using zip to mimic concurrency since both responses have same CDA response structure.
 * you can pass N number of observables with result selector method as the last argument.
 * concatMap ensures order of results with our chained promises
 * indentation shows an additional action/observable that is pushed into the sequence
 * our sequence blueprint:
 *
 *          zip ( status observable and custom views observable )
 *          concat datamart preferences observable
 *          concat get count observable
 *          stream = [ [status, customViews], [preferences], [count] ]
 *
 * all the observables are flattened into one event stream which we then subscribe to
 * onNext() will be fired when the final result is ready which renders our grid
 */

var getGridDataSequence = Rx.Observable.zip(statusObs, getCustomViewsObs, service.setupDMwithCustomViews)
    .concatMap((dataMart) => {
        // Compute dataView properties based on profile and search criteria
        var dataViewProperties = detailsGridSvc.getViewProperties(dataMart.profile, dataMart.searchCriteria);

        // Get mart preferences and count and prepare Kendo grid for loading data
        return dataMartSvc.getPreferences(dataMart.properties.tableName, dataMart.profile)
            .concatMap((preferences) => {

                var dataMartProperties = detailsGridSvc.createFiltersAndSorts(preferences, dataMart, dataViewProperties);

                if (customViewsSvc.isCustomView(dataMart.profile)) {
                    dataMartProperties = customViewsSvc.getIntersectedFiltersAndSorts(dataMartProperties);
                }

                // Then get total row count
                return detailsGridSvc.getCount(dataMartProperties.properties.tableId, dataMartProperties.filters)
                    .map((filterCount) => {

                        dataMartProperties.filterCount = filterCount;

                        return dataMartProperties;
                    })
                    .retry(3); // count request is unstable, try 3x
        }
})
.takeUntil(controllerScopeIsDestroyed) // kill async sequence when controller is destroyed
.take(1); // just run it once on INIT


getGridDataSequence.subscribe({
    onNext(dataMart) {
        var dataSource = detailsGridSvc.createKendoGridHybridDataSource(AppSettings.pentaho.queryPath, dataMart);
        // send dataMart properties and dataSource to create Grid
        detailsGridSvc.createGrid(dataMart, dataSource);
    },
    onError(err) {
        spinnerSvc.stop('spinner-details-container');
    },
    onCompleted() {
        // update scope model to fire digest cycle and show grid
        $scope.isReady = true;
    }
});