How to get directions between two addresses in iOS

I'm using this code to try get directions between two locations. But it outputs co-ordinates using latitude and longitude. But what I want is to get directions for searching based on 2 addresses. How can I get this code to work with addresses?

MKPlacemark *source = [[MKPlacemark alloc]initWithCoordinate:CLLocationCoordinate2DMake(37.776142, -122.424774) addressDictionary:[NSDictionary dictionaryWithObjectsAndKeys:@"",@"", nil] ];

MKMapItem *srcMapItem = [[MKMapItem alloc]initWithPlacemark:source];
[srcMapItem setName:@""];

MKPlacemark *destination = [[MKPlacemark alloc]initWithCoordinate:CLLocationCoordinate2DMake(37.73787, -122.373962) addressDictionary:[NSDictionary dictionaryWithObjectsAndKeys:@"",@"", nil] ];

MKMapItem *distMapItem = [[MKMapItem alloc]initWithPlacemark:destination];
[distMapItem setName:@""];

MKDirectionsRequest *request = [[MKDirectionsRequest alloc]init];
[request setSource:srcMapItem];
[request setDestination:distMapItem];
[request setTransportType:MKDirectionsTransportTypeAny];

MKDirections *direction = [[MKDirections alloc]initWithRequest:request];

[direction calculateDirectionsWithCompletionHandler:^(MKDirectionsResponse *response, NSError *error) {

    NSLog(@"response = %@",response);
    NSArray *arrRoutes = [response routes];
    [arrRoutes enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

        MKRoute *rout = obj;

        MKPolyline *line = [rout polyline];
        [mapview addOverlay:line];
        NSLog(@"Rout Name : %@",rout.name);
        NSLog(@"Total Distance (in Meters) :%f",rout.distance);

        NSArray *steps = [rout steps];

        NSLog(@"Total Steps : %lu",(unsigned long)[steps count]);
        NSMutableArray *stepsArray=[[NSMutableArray alloc] init];
        [steps enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
            NSLog(@"Rout Instruction : %@",[obj instructions]);
            NSLog(@"Rout Distance : %f",[obj distance]);
            [stepsArray addObject:[obj instructions]];
        }];

        [self myShowDirections:response];
        self.steps.text=[NSString stringWithFormat:@"%@",stepsArray];

via Chebli Mohamed