Find the number of routes between two places - objective-c

Question

I need to find out the number of routes from a source to a destination using the Google maps API, and then find, among those, which one is the shortest route.
I am able to get one route by using this code
-(NSArray*) calculateRoutesFrom:(CLLocationCoordinate2D) f to: (CLLocationCoordinate2D) t {
NSString* saddr = [NSString stringWithFormat:#"%f,%f", f.latitude, f.longitude];
NSString* daddr = [NSString stringWithFormat:#"%f,%f", t.latitude, t.longitude];
NSString* apiUrlStr = [NSString stringWithFormat:#"http://maps.google.com/maps?output=dragdir&saddr=%#&daddr=%#", saddr, daddr];
NSURL* apiUrl = [NSURL URLWithString:apiUrlStr];
NSLog(#"api url: %#", apiUrl);
NSString *apiResponse = [NSString stringWithContentsOfURL:apiUrl];
NSString* encodedPoints = [apiResponse stringByMatching:#"points:\\\"([^\\\"]*)\\\"" capture:1L];
return [self decodePolyLine:[encodedPoints mutableCopy]];
}
but I'm unable to get multiple routes.
I'm new to using the Google Maps API; I followed this tutorial.
How can I do this? Can any one please post some sample code or a tutorial?

Answer 1

alternatives (optional), if set to
true, specifies that the Directions
service may provide more than one
route alternative in the response.
Note that providing route alternatives
may increase the response time from
the server.
From The Google Directions API
You need to add in your query link alternatives=true

Answer 2

For getting the multiple routes you have to use the standard google direction api. Through this api you can get different routes on the bases of traveling mode you select in api ie driving, walking or bicycling( bicycling route availabel in US only) For example : http://maps.googleapis.com/maps/api/directions/xml?origin=srcLatitude,srcLongitude&destination=destLatitude,destLongitude&mode=driving&sensor=false
Here you can give the source and destination latitude and longitude and change the value of mode parameter to driving, walking or bicycling to get multiple route.