Feature Layer Query never enters delegate methods

Question

I am trying to load in a bunch of features from a feature service on arcgis.com. I know the service is coming in just fine because it renders on the map. What I can't get it to do is to let me read out the features themselves.

To my knowledge, I need to make a query on this feature layer and then I can parse out the results in a delegate method. However, my delegate method is never getting called, making me wonder if I am missing a step somewhere.

Below is my code: 
 (void)viewDidLoad {
    [super viewDidLoad];
    
    AGSLocalTiledLayer *localLayer = [AGSLocalTiledLayer localTiledLayerWithName:@myname];
    [self.mapView addMapLayer:localLayer withName:@Campus Basemap];
   
    NSURL *url = [NSURL URLWithString:@myservicename];
    AGSFeatureLayer *buildingPoints = [AGSFeatureLayer featureServiceLayerWithURL:url mode:AGSFeatureLayerModeOnDemand];
    [self.mapView addMapLayer:buildingPoints withName:@BYU Buildings];
    
    //set myself as the query's delegate
    buildingPoints.queryDelegate = self;
    
    AGSQuery *query = [AGSQuery query];
    //no "where" clause because I want all the records
    query.outFields = [NSArray arrayWithObjects:@FID, @Abbr, @Name, nil];
    [buildingPoints selectFeaturesWithQuery:query selectionMethod:AGSFeatureLayerSelectionMethodNew];
    
    [self.mapView.locationDisplay startDataSource];
}

- (void)featureLayer:(AGSFeatureLayer *)featureLayer operation:(NSOperation *)op didQueryFeaturesWithFeatureSet:(AGSFeatureSet *)featureSet {
    //IT NEVER GETS IN HERE!
    //populate all the points into an nsarray.
    for (AGSGraphic *selectedFeature in featureSet.features){
        Building *building = [[Building alloc] init];
        building.fid = [[selectedFeature attributeForKey:@FID] integerValue];
        building.abbreviation = [selectedFeature attributeAsStringForKey:@Abbr];
        building.fullName = [selectedFeature attributeAsStringForKey:@Name];
    }
}

- (void)featureLayer:(AGSFeatureLayer *)featureLayer operation:(NSOperation *)op didFailSelectFeaturesWithError:(NSError *)error {
    //IT NEVER GETS HERE EITHER
    NSLog(@Query Failed.);
}

Any ideas?

HrishikeshPol · Answer

Hey Nimesh,

I have created instance variable for AGSFeatureLayer but still facing some issues. Below is the code from which I'm uploading 3 feature layers on basemap. I'm able to load it but it is not consistent.

Please let me know if I'm making some mistake. Thank you in advance.

// Add basemap.

NSURL* url = [NSURL URLWithString: @"http://services.arcgisonline.com/arcgis/rest/services/World_Topo_map/mapserver"];

AGSTiledMapServiceLayer* layer = [AGSTiledMapServiceLayer tiledMapServiceLayerWithURL: url];

layer.delegate = self;

[self.mapView addMapLayer:layer withName:@Streets];

//zoom to an area

AGSEnvelope *envelope = [AGSEnvelope envelopeWithXmin:-1.34732920649E7 ymin:4533851.309500001 xmax:-1.3431785844E7

ymax:4641521.468800001  spatialReference:self.mapView.spatialReference];

[self.mapView zoomToEnvelope:envelope animated:NO];

// Structures.

NSString *urlString = [self.currentWorkOrder.detectionURL substringToIndex:[self.currentWorkOrder.detectionURL length]-1];

self.featureLayerURL0 = [NSURL URLWithString:[NSString stringWithFormat:@%@0",urlString]];

self.featureLayer0 = [AGSFeatureLayer featureServiceLayerWithURL:self.featureLayerURL0 mode:AGSFeatureLayerModeOnDemand];

self.featureLayer0.delegate = self;

[self.mapView addMapLayer:self.featureLayer0 withName:@CloudData0];

// Alignment.

self.featureLayerURL = [NSURL URLWithString:[NSString stringWithFormat:@%@1",urlString]];

self.featureLayer = [AGSFeatureLayer featureServiceLayerWithURL:self.featureLayerURL mode:AGSFeatureLayerModeOnDemand];

self.featureLayer.delegate = self;

[self.mapView addMapLayer:self.featureLayer withName:@CloudData];

// Detections.

self.featureLayerURL1 = [NSURL URLWithString:[NSString stringWithFormat:@%@2",urlString]];

self.featureLayer1 = [AGSFeatureLayer featureServiceLayerWithURL:self.featureLayerURL1 mode:AGSFeatureLayerModeOnDemand];

self.featureLayer1.delegate = self;

PO(self.featureLayer1.fields);

[self.mapView addMapLayer:self.featureLayer1 withName:@CloudData1];

self.featureLayer1.queryDelegate = self;

AGSQuery *query = [AGSQuery query];

//no "where" clause because I want all the records

query.outFields = [NSArray arrayWithObjects:@Detection, @Health, @Circuit, nil];

[self.featureLayer1 selectFeaturesWithQuery:query selectionMethod:AGSFeatureLayerSelectionMethodNew];

[self.mapView.locationDisplay startDataSource];

NimeshJarecha · Answer

It's because your local variable of AGSFeatureLayer get released before delegate method is called. Either create an instance variable for AGSFeatureLayer or create strong/retain property.

Regards,
Nimesh