Question

I decided to try and make a Singleton for use with locations. I have got what I think to be, the singleton working correctly however I have one error that is now appearing. It tells me that my implementation is incomplete. It is the only error it is giving me and I am sure it is something wrong with either my view header or m file. I have tried a few things now and cannot get it to work. What am I missing here?

Here is my header

#import <UIKit/UIKit.h>

@interface TrackerViewController : UIViewController
-(void) locationUpdate;
end

And here is my implementation file:

#import "TrackerViewController.h"
#import "MyLocation.h"

@implementation TrackerViewController

NSString *LatCoord;
NSString *LongCoord;

- (void)didReceiveMemoryWarning
{
  [super didReceiveMemoryWarning];
  // Release any cached data, images, etc that aren't in use.
}

#pragma mark - View lifecycle

- (void)viewDidLoad
{
  [super viewDidLoad];
  [LocationController sharedInstance].locDelegate = (id)self;
  // Do any additional setup after loading the view, typically from a nib.
}

- (void)viewDidUnload
{
  [super viewDidUnload];
  // Release any retained subviews of the main view.
  // e.g. self.myOutlet = nil;
}

- (void)viewWillAppear:(BOOL)animated
{
  [super viewWillAppear:animated];
}

- (void)viewDidAppear:(BOOL)animated
{
  [super viewDidAppear:animated];
}

- (void)viewWillDisappear:(BOOL)animated
{
  [super viewWillDisappear:animated];
}

- (void)viewDidDisappear:(BOOL)animated
{
  [super viewDidDisappear:animated];
}

- (void)locationUpdate:(CLLocation *)location {
    [[LocationController sharedInstance] setLocation:location];
    LatCoord  = [NSString stringWithFormat:@"%lf", location.coordinate.latitude];
    LongCoord = [NSString stringWithFormat:@"%lf", location.coordinate.longitude];
}

- (BOOL)shouldAutorotateToInterfaceOrientation (UIInterfaceOrientation)interfaceOrientation
{
  // Return YES for supported orientations
  return YES;
}

-(IBAction)CheckIn:(id)sender 
{
  [self locationUpdate];
}

@end

My singleton header is as follows:

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

@protocol LocationControllerDelegate <NSObject>
@required
- (void)locationUpdate:(CLLocation*)location;
@end

@interface LocationController : NSObject <CLLocationManagerDelegate> {

  __unsafe_unretained id <LocationControllerDelegate> _locDelegate;

  CLLocationManager* locationManager;
  CLLocation* location;
  id locDelegate;
}

@property (nonatomic, retain) CLLocationManager* locationManager;
@property (nonatomic, retain) CLLocation* location;
@property (nonatomic, assign) id <LocationControllerDelegate> locDelegate;

+ (LocationController*)sharedInstance;

@end

My singleton implementation is as follows:

#import "MyLocation.h"

static LocationController* sharedCLDelegate = nil;

@implementation LocationController
@synthesize locationManager, location, locDelegate = _locDelegate;

- (id)init
{
 self = [super init];
 if (self != nil) {
   self.locationManager = [[CLLocationManager alloc] init];
   self.locationManager.delegate = self;
   self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
 }
 return self;
}

- (void)dealloc
{
 /* ... */
}

#pragma mark -
#pragma mark CLLocationManagerDelegate Methods
- (void)locationManager:(CLLocationManager*)manager
   didUpdateToLocation:(CLLocation*)newLocation
       fromLocation:(CLLocation*)oldLocation
{
 /* ... */
}

- (void)locationManager:(CLLocationManager*)manager
    didFailWithError:(NSError*)error
{
  /* ... */

}

#pragma mark -
#pragma mark Singleton Object Methods

+ (LocationController*)sharedInstance {
  @synchronized(self) {
    if (sharedCLDelegate == nil) {
    }
  }
  return sharedCLDelegate;
}

+ (id)allocWithZone:(NSZone *)zone {
  @synchronized(self) {
    if (sharedCLDelegate == nil) {
        sharedCLDelegate = [super allocWithZone:zone];
        return sharedCLDelegate;  
    }
  }
  return nil;
}

- (id)copyWithZone:(NSZone *)zone
{
  return self;
}


@end

What am I missing or doing wrong here?

Answer 1

Your singleton looks wrong. Your sharedInstance method should be:

+ (LocationController*)sharedInstance {
  @synchronized(self) {
    if (sharedCLDelegate == nil) {
      sharedCLDelegate = [[self alloc] init];
    }
  }
  return sharedCLDelegate;
}

And you can get rid of the allocWithZone: and copyWithZone: methods – they don’t do anything useful.

That’s most likely why your class isn’t working, but probably has nothing to do with the “incomplete implementation” warning. The warning will be because you’ve forgotten to implement a method that’s declared in your header or in one of your protocols, or maybe you’ve misspelled it. I couldn’t spot it on a first pass, but I’ll take another look.

If you double-click on the yellow warning icon in the header it should tell you which method hasn’t been implemented properly.

By the way, the line below leaks because you’re double-retaining (init sets retain count to one, and then assigning to a retained property sets it to 2). You should run the Analyze function, which will add blue warnings for leaks like this.

self.locationManager = [[CLLocationManager alloc] init];

Do one of the following instead:

//assign directly to the ivar so the setter method isn't used
locationManager = [[CLLocationManager alloc] init];

Or

//autorelease before assigning
self.locationManager = [[[CLLocationManager alloc] init] autorelease];