Set annotation's title as current address

Question

I want to get the current location's address and set it to the annotation's title. But it didn't work. I think it's because of the block, but I don't know how to fix it. Any help will be appreciated. The most related code is as following:

WhereAmIAnnotation.h

#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>

@interface WhereAmIAnnotation : NSObject <MKAnnotation>
{
CLLocation *myLocation;
NSString *addr;
}
@property (nonatomic, retain) CLLocation *myLocation;
@property (nonatomic, copy) NSString *addr;

@end

WhereAmIAnnotation.m

#import "WhereAmIAnnotation.h"

@implementation WhereAmIAnnotation
@synthesize myLocation, addr;

- (CLLocationCoordinate2D)coordinate;
{
return self.myLocation.coordinate; 
}

- (NSString *)title
{  
return self.addr;
}
@end

MapViewController.m

- (IBAction)gotoCurrentLocation{
self.mapView.showsUserLocation = YES;//a bar button linked with this action
}

- (void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation
{    
CLLocation *currentLocation = userLocation.location;

MKCoordinateRegion newRegion; 
newRegion.center = currentLocation.coordinate;
newRegion.span.latitudeDelta = 0.02;
newRegion.span.longitudeDelta = 0.02;
[self.mapView setRegion:newRegion animated:YES];

WhereAmIAnnotation *whereAmIAnnotation = [[WhereAmIAnnotation alloc] init];
whereAmIAnnotation.myLocation = currentLocation;
whereAmIAnnotation.addr = [self addrAtLocation:currentLocation];

[self.mapView addAnnotation:whereAmIAnnotation];

self.mapView.showsUserLocation = NO;
}

- (NSString *)addrAtLocation:(CLLocation *)location{
[self.geocoder reverseGeocodeLocation:location completionHandler:^(NSArray *placemark, NSError *error) {
    CLPlacemark *topResult = [placemark objectAtIndex:0]; 
    self.addr = [NSString stringWithFormat:@"%@ %@ %@ %@", topResult.country, topResult.locality, topResult.subLocality, topResult.thoroughfare];
}];
return self.addr;
}

I should implement this method

- (MKAnnotationView *)mapView:(MKMapView *)theMapView viewForAnnotation:(id )annotation{}

sorry for this stupid question!

Does this code compile? In WhereAmIAnnotation.m, geocoder is synthesized but it's not declared. In the addrAtLocation method in MapViewController.m, it refers to self.addr but isn't addr a property in WhereAmIAnnotation? — , May 17 '12 at 13:24

Sam · Answer 1 · 2012-05-17T15:31:32.497

3

You are returning the address while modifying it inside an asynchronous block. You should move the return inside the block, or a create a protocol to handle passing this information back to the caller.

Change the block to this:

- (void)addrAtLocation:(CLLocation *)location{
    [self.geocoder reverseGeocodeLocation:location completionHandler:^(NSArray *placemark, NSError *error) {
        CLPlacemark *topResult = [placemark objectAtIndex:0];
        whereAmIAnnotation.addr = [NSString stringWithFormat:@"%@ %@ %@ %@", topResult.country, topResult.locality, topResult.subLocality, topResult.thoroughfare];
    }];
}

Then make whereAmIAnnotation a member variable. Do you understand WHY this fixes your issues?

edited May 17 '12 at 15:31

answered May 17 '12 at 14:29

Sam

2,579
17
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could you plz show me some related code to create a protocol to handle passing this information back to the caller? I will appreciate it very much:) – lu yuan May 17 '12 at 14:33
I make whereAmIAnnotation as a property, but still don't work. – lu yuan May 17 '12 at 16:26

score 0 · Answer 2 · answered May 17 '12 at 11:08

0

Create .h file

@interface MapPinClass : NSObject <MKAnnotation>{
CLLocationCoordinate2D coordinate; 
NSString *title; 
NSString *subtitle,*color,*index,*locationId;

}

@property (nonatomic, assign) CLLocationCoordinate2D coordinate; 
@property (nonatomic, copy) NSString *title;
@property (nonatomic, copy) NSString *subtitle,*color,*index,*locationId;

Create .m file

@implementation MapPinClass
@synthesize coordinate,title,subtitle,color,index,locationId;

-(void)dealloc{
[title release];
[super dealloc];

}

write a code where you set

 MapPinClass *ann = [[MapPinClass alloc] init]; 
ann.title = AppMain.Heading;
ann.subtitle = AppMain.Detail; 
ann.coordinate = region.center; 
[myMapView addAnnotation:ann];

answered May 17 '12 at 11:08

Abhishek Patel

71
4
12

thx for your answer. But i do not understand here "ann.title = AppMain.Heading; ann.subtitle = AppMain.Detail; " – lu yuan May 17 '12 at 11:25
this class give you two things 1st is heading and 2nd is his detail, so you can set you text in ann.title=@"Yourheading"; and ann.subtitle= @"this is detail text"; – Abhishek Patel May 17 '12 at 11:32
MKUserLocation class? I have tried your codes, seems not working. – lu yuan May 17 '12 at 11:35
have you add framework - corelocation and mapkit...?? did you get error .? – Abhishek Patel May 17 '12 at 11:47
Yes, I do add them, and without error. What's your AppMain.Heading and AppMain.Detail? I wanna get the current address. – lu yuan May 17 '12 at 11:48
you mean you need current longitude and latitude...?? – Abhishek Patel May 17 '12 at 11:49
AppMain.Heading is a simple NSString that i define in Delegate. – Abhishek Patel May 17 '12 at 11:49
- (NSString *)addrAtLocation:(CLLocation *)location{ [self.geocoder reverseGeocodeLocation:location completionHandler:^(NSArray *placemark, NSError *error) { CLPlacemark *topResult = [placemark objectAtIndex:0]; self.addr = [NSString stringWithFormat:@"%@ %@ %@ %@", topResult.country, topResult.locality, topResult.subLocality, topResult.thoroughfare]; }]; return self.addr; } – lu yuan May 17 '12 at 11:56
you want current location detail from tapping on map...?? – Abhishek Patel May 17 '12 at 12:09
I have a button to get current location, and use reverseGeocodeLocation to get the address. and i wanna my annotation to display the addr – lu yuan May 17 '12 at 13:23

score 0 · Accepted Answer · edited May 25 '15 at 17:07

0

I should implement this method

- (MKAnnotationView *)mapView:(MKMapView *)theMapView viewForAnnotation:(id <MKAnnotation>)annotation{}

Sorry for that stupid question.

edited May 25 '15 at 17:07

Ashish Kakkad

23,586
12
103
136

answered May 17 '12 at 18:18

lu yuan

7,207
9
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@kevboh Did you have the same problem? – lu yuan May 18 '12 at 05:33
No, I meant "that works if you accept your answer in 2 days" :) – kevboh May 18 '12 at 11:38

Set annotation's title as current address

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