IOS中地图中当前位置最近的位置

Question

Have a button on a mapview which is used to calculate the nearest location from the locations i have plotted on map. I have applied some code but when i click the button the app crashes by giving this error,

[__NSDictionaryI coordinate]: unrecognized selector sent to instance 0x174e61b40 2017-10-31 15:20:00.434548 GuardsAutoZone[735:114166] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryI coordinate]: unrecognized selector sent to instance 0x174e61b40' * First throw call stack: (0x1937d11b8 0x19220855c 0x1937d8268 0x1937d5270 0x1936ce80c 0x10011cec8 0x1996bbd30 0x1996bbcb0 0x1996a6128 0x1996bb59c 0x1996bb0c4 0x1996b6328 0x199686da0 0x199e7075c 0x199e6a130 0x19377eb5c 0x19377e4a4 0x19377c0a4 0x1936aa2b8 0x19515e198 0x1996f17fc 0x1996ec534 0x1000fc994 0x19268d5b8) libc++abi.dylib: terminating with uncaught exception of type NSException (lldb)

My code is this, i'm in doubt that my code is right for finding nearest location or not? The code i used is,

- (IBAction)nearLocation:(id)sender {
CLLocation *userLocation = self.mapView.userLocation.location;
NSMutableDictionary *distances = [NSMutableDictionary dictionary];

for (MapPin *obj in locations) {
    CLLocation *loc = [[CLLocation alloc] initWithLatitude:obj.coordinate.latitude longitude:obj.coordinate.longitude];
    CLLocationDistance distance = [loc distanceFromLocation:userLocation];

    NSLog(@"Distance from Annotations - %f", distance);

    [distances setObject:obj forKey:@( distance )];


}

NSArray *sortedKeys = [distances allKeys];
NSLog(@"List %@",sortedKeys);
//NSArray *closestKeys = [sortedKeys subarrayWithRange:NSMakeRange(0, MIN(3, sortedKeys.count))];

 // NSArray *closestAnnotations = [distances objectsForKeys:closestKeys notFoundMarker:[NSNull null]];


}

the error screen shot is , enter image description here

Answer 1

Use this set of code to get the distance between two latitude and longitude.

In Objective C

@class CLLocation

CLLocation *location1 =[[CLLocation alloc] initWithLatitude:[@"23.039698" doubleValue] longitude:[@"77.571663" doubleValue]];
CLLocation *location2 = [[CLLocation alloc] initWithLatitude:[@"23.0422" doubleValue] longitude:[@"72.5644" doubleValue]];
CLLocationDistance distanceMeter = [location distanceFromLocation:location2];

And in Swift

import CoreLocation

let location1 = CLLocation(latitude: 5.0, longitude: 5.0)
let location2 = CLLocation(latitude: 5.0, longitude: 3.0)

let distanceInMeters = location1.distance(from: location2)

The above code will give you the distance in meters.

Once you will get the distance between the two annotation through the coordinate then you can implement the same as per your requirement.

Answer 2

It seems locations is an array of NSDictionary . In the for loop you cast the elements to MapPin* but that just makes the compiler happy. Accessing obj.coordinate.latitude will call selector coordinate on object obj . And the exception tells us its an NSDictionary object.

Check what kind of object locations really is at runtime and change your code accordingly.