在Xcode 4.5中将CLLocationCoordinate2D发送到不兼容类型的参数我的代码

Question

I am new to Xcode. I am developing a vehicle tracking app for that I need to display more annotation points simultaneously. For this I need to store the coordinates in the array but it shows the error: Sending CLLocationCoordinate2D to parameter of incompatible type
my code is:

NSString *urlMapString=[NSString stringWithFormat:@"http://logix.com/logix_webservice/mapvehiclelist.php?uid=20&format=json"];
NSURL *urlMap=[NSURL URLWithString:urlMapString];
NSData *dataMap=[NSData dataWithContentsOfURL:urlMap];
if(dataMap!=NULL){
   NSError *errorMap;
   NSMutableArray *coordinates = [[NSMutableArray alloc]init];
   NSDictionary *jsonMap = [NSJSONSerialization JSONObjectWithData:dataMap options:kNilOptions error:&errorMap];
   NSArray *resultsMap = [jsonMap valueForKey:@"posts"];
   for(int count=1;count<resultsMap.count;count++)
      {
       NSDictionary *resMap = [[resultsMap objectAtIndex:count]valueForKey:@"post"];
       NSString *latOrgstring =[resMap valueForKey:@"latitude"];
       latitude=[latOrgstring doubleValue];
       NSString *longitudeString=[resMap valueForKey:@"longitude"];
       longitude=[longitudeString doubleValue];
       //Center
       CLLocationCoordinate2D center;
       center.latitude=latitude;
       center.longitude=longitude;
       [coordinates addObject:center]; //here it shows the error
      }
}

Kindly advice me to solve this problem.
Thank you...

Answer 1

CLLocationCoordinate2D center isn't an object. You can store only objects in NSArray. Use CLLocation for this.

CLLocation *location = [[CLLocation alloc] initWithLatitude:lat longitude:lon];

Answer 2

As already mentioned, you can only add objects to an NSArray .

CLLocationCoordinate2D is not an object -- it is a C struct.

The code you posted itself has one solution:
Create a NSDictionary with the latitude and longitude as key/value pairs and add the resulting dictionary object to the array.

Another approach is to create a CLLocation as shown in another answer.

A third idea is what @trojanfoe answered previously which is to wrap the struct in an NSValue .

However , note that there is a convenient NSValue addition specifically for MapKit that adds these two useful helper methods:

• valueWithMKCoordinate: which returns an NSValue given a CLLocationCoordinate2D
• MKCoordinateValue which returns a CLLocationCoordinate2D for the NSValue

For an example, see How to store CLLocationCoordinate2D? .

A final (at least in this answer) alternate approach which I would highly recommend instead of all the above is this...

• Why do you want to store only the coordinates in an array?
• Wouldn't you want to know what the coordinates are for (which vehicle, place, etc)?
• Why not create a custom class that implements, say, the MKAnnotation protocol and has not only the coordinates (as a CLLocationCoordinate2D property) but also all the other information related to the coordinate ? The class would be a subclass of NSObject<MKAnnotation> .
• You could then conveniently access all the information in one place without using multiple arrays and trying to keep the objects in the same order so they all have the same index, etc.
• You could then directly add these objects to an MKMapView since they implement MKAnnotation .

Answer 3

CLLocationCoordinate2D is a C struct, so you need to put it in NSValue container at first.

An NSValue object is a simple container for a single C or Objective-C data item. It can hold any of the scalar types such as int, float, and char, as well as pointers, structures, and object id references. Use this class to work with such data types in collections (such as NSArray and NSSet), key-value coding, and other APIs that require Objective-C objects.

[coordinates addObject:[NSValue value:&coordinate withObjCType:@encode(CLLocationCoordinate2D)]];

Answer 4

Try this

CLLocationCoordinate2D new_coordinate = CLLocationCoordinate2DMake(latitude, longitude);
[points addObject:[NSValue valueWithMKCoordinate:new_coordinate]];

Or

CLLocation *location = [[CLLocation alloc] initWithLatitude:lat longitude:lon];
[coordinates addObject: location];

Can't u directly add coordinates to mapview that means Place MKAnnotation on Mapview, instead of taking coordinates to into array ?

SEE Below i commented with lines

for(int count=1;count<resultsMap.count;count++)
  {
   NSDictionary *resMap = [[resultsMap objectAtIndex:count]valueForKey:@"post"];
   NSString *latOrgstring =[resMap valueForKey:@"latitude"];
   latitude=[latOrgstring doubleValue];
   NSString *longitudeString=[resMap valueForKey:@"longitude"];
   longitude=[longitudeString doubleValue];
   //Center
   CLLocationCoordinate2D center;
   center.latitude=latitude;
   center.longitude=longitude;
    -----------------------------------------
  ////// Annotation is MKAnnotation Subclass
    Annotation * cartAnn = [Annotation new]; 
    cartAnn.coordinate = center; 
    [self.mapView addAnnotation: cartAnn];
  ----------------------------------------------------
  /////// [coordinates addObject:center]; //here it shows the error
  }