topic Re: Calling queryTask in a loop in ArcGIS Runtime SDK for iOS Questions

Calling queryTask in a loop

MiriEshel — Thu, 27 Oct 2011 15:25:48 GMT

Hi,

I'm trying to call queryTask in a loop but it looks like it refers only to the last call, i.e. it enters to didExecuteWithFeatureSetResult only in the last call).

Is there a way to force it to work asynchronously?

Here is the chunk of code I'm using:

for (NSDictionary *r in res)
{
   NSString *layer = [r objectForKey:@"layerId"] ;

   NSString *objectsID = @"";

   NSArray *features = [r objectForKey:@"features"];
   for (NSDictionary *feature in features) {
    NSString *objectID = [feature objectForKey:@"OBJECTID"];
    objectsID = [NSString stringWithFormat:@"%@ , %@",objectsID, objectID];
   }
   //Remove first ,
   objectsID = [objectsID substringFromIndex:2];

   //objectsID = @"OBJECTID IN (";
   objectsID = [NSString stringWithFormat:@"%@ %@", @"OBJECTID IN (", objectsID];
   objectsID = [NSString stringWithFormat:@"%@ )",objectsID];

   NSString *waterLayerURL =[NSString stringWithFormat:@"%@%@",@"http://mnatania10/ArcGIS/rest/services/GeneralView/MapServer/", layer];

   //set up query task against layer, specify the delegate
   self.queryTask = [AGSQueryTask queryTaskWithURL:[NSURL URLWithString:waterLayerURL]];
   self.queryTask.delegate = self;

   //return all fields in query
   self.query.where = objectsID;

   NSLog(@"name : %@", self.query.where);
   [self.queryTask executeWithQuery:self.query];


}

Thanks a lot,
Miri

Re: Calling queryTask in a loop

RickJones — Thu, 27 Oct 2011 18:15:39 GMT

In your for loop, objectsID is being reset each time, not appended to. Is this what you wanted?

When the loop finishes, only the last value will be in the variable.

Re: Calling queryTask in a loop

NimeshJarecha — Fri, 28 Oct 2011 19:54:20 GMT

Are you querying by where clause or objectIds? The code "self.query.where = objectsID;" seems incorrect.

Please attach a sample project, that'll help understand your code better.

Regards,
Nimesh

Re: Calling queryTask in a loop

ShaharBukra — Sun, 30 Oct 2011 07:54:13 GMT

Hi Nimesh,
Im working with miri...

we trying to do it by using where clause
the "objectids" you see is string with long query in it.

we try do it asnyc, but cant find how.

thanks,
have a great week

Shahar.

Re: Calling queryTask in a loop

DiveshGoyal — Mon, 31 Oct 2011 16:50:16 GMT

One reason why you may be experiencing the problem you describe is because you may be allocating the query task again and again in the loop. The following line of code -

self.queryTask = [AGSQueryTask queryTaskWithURL:[NSURL URLWithString:waterLayerURL]];

will release the previous instance of query task and create a new one. When the previous one is released, it will no longer invoke the delegate. (for more information, refer to apple's doc on objective-C properties)

If all your queries are against the same service, you should create the task only once, and call executeWithQuery: in a loop for each query.