MapKitAutocomplete.h

#import <React/RCTBridgeModule.h>
#import <MapKit/MapKit.h>


@interface MapKitAutocomplete : NSObject <RCTBridgeModule,MKLocalSearchCompleterDelegate>
@property (strong, nonatomic) MKLocalSearchCompleter *completer;
@end

MapKitAutocomplete.m

#import "MapKitAutocomplete.h"

@implementation MapKitAutocomplete

RCT_EXPORT_MODULE();

- (id)init {
  self = [super init];
  self.completer = [[MKLocalSearchCompleter alloc] init];
  self.completer.delegate = self;
  self.completer.queryFragment = @"LA"; // <--------------- Works
  return self;
}

RCT_EXPORT_METHOD(query:(NSString *)query)
{
  self.completer.queryFragment = query; // <--------------- Doesn't work
  NSLog(@"%@", query);
}

// XXX: This never gets called when `self.completer.queryFragment` is updated
- (void) completerDidUpdateResults:(MKLocalSearchCompleter *)completer {
  for (MKLocalSearchCompletion *completion in completer.results) {
    NSLog(@"------ %@", completion.description);
  }
}

- (void) completer:(MKLocalSearchCompleter *)completer didFailWithError:(NSError *)error {
  NSLog(@"Completer failed with error: %@", error.description);
}

@end