Geocoding many addresses - CLGeocoder - objective-c

Question

I need to geocode a ton of addresses with CLGeocoder, not the Google API.
My problem is that my code is only adding an annotation for the first address in the array below. However, the function gets called an appropriate number of times - the block just runs for the first address after the function has been called for ALL of the addresses:
- (void)mapPoints {
NSString *foo = [[NSBundle mainBundle] pathForResource:[NSString stringWithFormat:#"names%d", self.indexOfSchool] ofType:#"plist"];
NSArray *description = [NSArray arrayWithContentsOfFile:foo];
NSString *bar = [[NSBundle mainBundle] pathForResource:[NSString stringWithFormat:#"%d1", self.indexOfSchool] ofType:#"plist"];
NSArray *details = [NSArray arrayWithContentsOfFile:bar];
NSString *path = [[NSBundle mainBundle] pathForResource:[NSString stringWithFormat:#"%d0", self.indexOfSchool] ofType:#"plist"];
NSArray *addresses = [NSArray arrayWithContentsOfFile:path];
self.saved = [NSMutableArray alloc] init];
for (int q = 0; q < addresses.count; q+= 20) {
[self annotate:[addresses objectAtIndex:q] detail:[details objectAtIndex:q] andDesc:[description objectAtIndex:q]];
}
}
see updated annotate: method below...
Here are how my logs appear:
here
here
here
here
.
..
...
....
<MKPointAnnotation: 0x16fc12e0>
Therefore, although the function is being called with the loop, the block is not running for any results other than the first.
I know my addresses are good. This does not work for any number (>1) of calls to the function.
The += 20 in the loop has nothing to do with only one point being plotted: this does not work for ++ either (there are also around 200 results).
I'm fairly new to blocks, so hopefully this is an easy fix. Any help is greatly appreciated!
EDIT
Doing this instead:
- (void)annotate:(NSString *)address detail:(NSString *)detail andDesc:(NSString *)description {
CLGeocoder *geocoder = [[CLGeocoder alloc] init];
[geocoder geocodeAddressString:address
completionHandler:^(NSArray* placemarks, NSError* error) {
if (placemarks && placemarks.count > 0) {
CLPlacemark *topResult = [placemarks objectAtIndex:0];
MKPlacemark *placemark = [[MKPlacemark alloc] initWithPlacemark:topResult];
MKPointAnnotation *point = [[MKPointAnnotation alloc] init];
point.coordinate = placemark.coordinate;
point.title = description;
point.subtitle = [NSString stringWithFormat:#"%# miles from origin", detail];
MKCoordinateRegion region = self.directionsView.region;
region.center = [(CLCircularRegion *)placemark.region center];
region.span.longitudeDelta /= 8.0;
region.span.latitudeDelta /= 8.0;
[self.directionsView addAnnotation:point];
NSLog(#"%#", point);
[self.directionsView setRegion:region animated:YES];
}
}
];
[self.saved addObject:geocoder];
NSLog(#"%#", geocoder);
}
... still pulls up a blank map with no annotations -- not even the first. The geocoder array has a different memory address upon each call to the function, so that piece appears to be working.

Answer 1

You are calling the geocodeAddressString a few times in a row, but apple's docs say
After initiating a forward-geocoding request, do not attempt to
initiate another forward- or reverse-geocoding request.
So I think what is happening is either the current request is cancelled when you make a new one, or all new requests are ignored if one is already in progress.
As a workaround you could geocode one point, and then geocode the next point in the completion block or create multiple instances of the geocoder

Answer 2

Each CLGeocoder object can only process one request at a time. Try creating a new CLGeocoder object inside your annotate method instead of reusing a single object stored in a property. As long as you have ARC enabled, you should be okay.
Note that Apple may place restrictions on the number of simultaneous requests you send to their servers, so you may need to limit the number of outstanding requests if you're doing a large number of them.

Answer 3

You can have only one geocoding request running at a time regardless of how many instances of CLGeocoder you have. You will have to start another request from withing the completion block of the previous one.
Also, take into account, that geocoding too many addresses in a short time will reach its internal limit. In my experiments, after ~50 requests (one after another) the framework refused to process new requests for next ~60 seconds.

Answer 4

This is a Xamarin pseudo-code but it should work the same in native as I had to convert to C# in the first place:
forloop()
{
var geocoder = new CLGeocoder();
var placemarks = await geocoder.GeocodeAddressAsync(address);
}