Question

I have the following code in my app which adds a number of Annotations to a mapview via Google geocoding:

for (PlaceObject *info in mapLocations) {

    NSString * addressOne = info.addressOne;
    NSString * name = info.name;

    NSString * address = [addressOne stringByAppendingString:@",London"];

    NSError * error;

    NSString *urlString = [NSString stringWithFormat:@"http://maps.google.com/maps/geo?q=%@&output=csv", [address stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

    NSString *locationString = [NSString stringWithContentsOfURL:[NSURL URLWithString:urlString ] encoding:NSASCIIStringEncoding error:&error];
    NSArray *listItems = [locationString componentsSeparatedByString:@","];

    double latitude = 0.0;
    double longitude = 0.0;

    if([listItems count] >= 4 && [[listItems objectAtIndex:0] isEqualToString:@"200"]) {
        latitude = [[listItems objectAtIndex:2] doubleValue];
        longitude = [[listItems objectAtIndex:3] doubleValue];

    } else {
        //Error handling

    }        

    CLLocationCoordinate2D coordinate;
    coordinate.latitude = latitude;
    coordinate.longitude = longitude;
    MyLocation *annotation = [[[MyLocation alloc] initWithName:name address:address coordinate:coordinate] autorelease];
    [mapViewLink addAnnotation:annotation];

}

This works, however it takes a long time for the view to appear as it seems to wait until all objects in the array have been looped through (there are about 80).

Is there any way to make the view load and then for the pins to be added as they are created ?

Answer 1

How about this:

for (PlaceObject *info in mapLocations) {

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_async(queue, ^{

        // GET ANNOTATION INFOS
        NSString * addressOne = info.addressOne;
        NSString * name = info.name;

        NSString * address = [addressOne stringByAppendingString:@",London"];

        NSError * error;

        NSString *urlString = [NSString stringWithFormat:@"http://maps.google.com/maps/geo?q=%@&output=csv", [address stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];

        NSString *locationString = [NSString stringWithContentsOfURL:[NSURL URLWithString:urlString ] encoding:NSASCIIStringEncoding error:&error];
        NSArray *listItems = [locationString componentsSeparatedByString:@","];

        double latitude = 0.0;
        double longitude = 0.0;

        if([listItems count] >= 4 && [[listItems objectAtIndex:0] isEqualToString:@"200"]) {
            latitude = [[listItems objectAtIndex:2] doubleValue];
            longitude = [[listItems objectAtIndex:3] doubleValue];

        } else {
            //Error handling

        }        

        CLLocationCoordinate2D coordinate;
        coordinate.latitude = latitude;
        coordinate.longitude = longitude;
        MyLocation *annotation = [[[MyLocation alloc] initWithName:name address:address coordinate:coordinate] autorelease]; 

        dispatch_sync(dispatch_get_main_queue(), ^{

            // ADD ANNOTATION
            [mapViewLink addAnnotation:annotation];

        });

    });
}

But please consider to double-check this code. There are definitily things you should do about keeping the threads safe and avoid EXC_BAD_ACCESS.