Pass NSString from didUpdateLocations in NSObject to a UIViewController - ios

Question

I created an iOS project and I implemented didUpdateLocations to get my location in a NSObject. I want to get the longitude and the latitude from the delegate to a UIViewController but the result is always null even to test the addObserver I couldn't. In the bottom there is a sample that I did and it shows my location in the label. I implemented didUpdateLocations in the viewcontroller and without a NSObject Class.
This my code in the NSObject:
#import "GpsModel.h"
#implementation GpsModel{
CLLocation *crnLoc;
}
#synthesize locationManager;
#synthesize longitude;
#synthesize latitude;
- (void) initLocation {
locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager requestWhenInUseAuthorization];
[locationManager requestAlwaysAuthorization];
[locationManager startUpdatingLocation];
}
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error{
//[self showAlert];
}
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
crnLoc = [locations lastObject];
longitude = [NSString stringWithFormat:#"%.8f",crnLoc.coordinate.longitude];
latitude = [NSString stringWithFormat:#"%.8f",crnLoc.coordinate.longitude];
}
#end
and this is my ViewController :
#import "GpsViewController.h"
#interface GpsViewController ()
#end
#implementation GpsViewController{
CLLocationManager *locationManager;
}
#synthesize gpsView;
#synthesize gpsModel;
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
gpsView = [[GpsView alloc] initWithFrame:CGRectMake(0, 0, widthtScreen, heightScreen)];
[self.view addSubview:gpsView];
gpsModel = [GpsModel new];
[gpsModel initLocation];
gpsView.longitudeLabel.text = gpsModel.longitude;
[gpsView.longitudeLabel addObserver:self forKeyPath:#"text" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil];
gpsView.latitudeLabel.text = gpsModel.latitude;
[gpsView.latitudeLabel addObserver:self forKeyPath:#"text" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if(object == gpsView.longitudeLabel)
{
NSLog(#"long");
}
if(object == gpsView.latitudeLabel)
{
NSLog(#"lat");
}
}
#end
And this my code without the creation of a NSObject Class :
#interface GpsViewController ()
#end
#implementation GpsViewController{
CLLocationManager *locationManager;
CLLocation *crnLoc;
}
#synthesize gpsView;
#synthesize gpsModel;
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
gpsView = [[GpsView alloc] initWithFrame:CGRectMake(0, 0, widthtScreen, heightScreen)];
[self.view addSubview:gpsView];
[self initLocation];
}
- (void) initLocation {
locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self;
locationManager.desiredAccuracy = kCLLocationAccuracyBest;
[locationManager requestWhenInUseAuthorization];
[locationManager requestAlwaysAuthorization];
[locationManager startUpdatingLocation];
}
- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error{
[self showAlert];
}
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
crnLoc = [locations lastObject];
NSLog(#"position long : %#",[NSString stringWithFormat:#"%.8f",crnLoc.coordinate.longitude]);
NSLog(#"position lat : %#",[NSString stringWithFormat:#"%.8f",crnLoc.coordinate.latitude]);
gpsView.longitudeLabel.text = [NSString stringWithFormat:#"%.8f",crnLoc.coordinate.longitude];
[gpsView.longitudeLabel addObserver:self forKeyPath:#"text" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil];
gpsView.latitudeLabel.text = [NSString stringWithFormat:#"%.8f",crnLoc.coordinate.latitude];
[gpsView.latitudeLabel addObserver:self forKeyPath:#"text" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:nil];
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
if(object == gpsView.longitudeLabel)
{
NSLog(#"observe1");
}
if(object == gpsView.latitudeLabel)
{
NSLog(#"observe2");
}
}
and this is my view that contains 2 labels
#implementation GpsView{
CGFloat _originY;
}
#synthesize longitudeLabel;
#synthesize latitudeLabel;
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
_originY = 50;
[self _initView];
}
return self;
}
- (id)initWithCoder:(NSCoder *)aDecoder {
if ((self = [super initWithCoder:aDecoder])) {
[self _initView];
}
return self;
}
- (void)_initComponents {
longitudeLabel = [[UILabel alloc] init];
latitudeLabel = [[UILabel alloc] init];
}
- (void)_initView {
[self _initComponents];
[self _createComponentView];
}
-(void) _createComponentView {
_originY = [self createLabel:_originY :longitudeLabel :self];
[self addSubview:longitudeLabel];
_originY = [self createLabel:_originY :latitudeLabel :self];
[self addSubview:latitudeLabel];
}

Answer 1

You are observing text in a label, that is set only once in your didLoad method and it will never be updated after the location update. If you want to use observers you should observe your gpsModel instance and latitude/longitude properties in it. And in the observeValueForKeyPath delegate method you should update your text labels.