Get User Current Location

Location service improve the app by enhancing user experience. Lots of application's features base on location service like finding near places, restaurant and whatever user want to search. Uber, Ola, Nearby and tons of applications are based on location service and display required content on the basis of that. Suppose we are stand on a place and want to search restaurant near current location, in this case we must know user current location and than can display result according to user search.
Now question is how can we get user current location? It is not a difficult task, every language provide in build framework and library for perform this task.
 Apple provide Core Location Framework for obtaining all necessary information regarding user's current location. Core Location Framework provide geographic location of device. Click here to know about Geographic coordinate system.

Lets start the coding stuff to fetch current location of a user.
Add Core Location Framework in the build phase of target under"Link Binary with Library"  section, switch to controller class and import location framework and implement <CLLocationManagerDelegate> and declare an instance of CLLocationManager.

#import <CoreLocation/CoreLocation.h>
@interface HomeMapViewController : UIViewController<CLLocationManagerDelegate>{
            CLLocationManager *locationManager;
}
@end

Now switch to .m class and add method for fetch current location

@implementation HomeMapViewController
      - (void)viewDidLoad {
              [super viewDidLoad];
              // Do any additional setup after loading the view from its nib.
               [self  getCurrentLocation];
       }
     -(void) getCurrentLocation{
         locationManager = [[CLLocationManager alloc] init];
         locationManager.delegate = self;
         locationManager.desiredAccuracy = kCLLocationAccuracyBest;
         if ([locationManager respondsToSelector:@selector(requestWhenInUseAuthorization)]) {
             [locationManager requestWhenInUseAuthorization];
         }
         [locationManager startUpdatingLocation];
     }
// define delegate methods of <CLLocationManagerDelegate>
      - (void)locationManager:(CLLocationManager *)manager
         didFailWithError:(NSError *)error{
          NSLog(@"Error to fetch location = %@", error);
     }
     -(void) locationManager:(CLLocationManager *)manager didUpdateLocations:               (NSArray<CLLocation *> *)locations{
         CLLocation *location = [locations lastObject];
         CLLocationCoordinate2D cord = location.coordinate;
         NSLog(@"Current Location\n Latitude - %f \n Longitude - %f", cord.latitude, cord.longitude);
     }@end

Now run the app and allow the application to fetch your current location.
You can see latitude and longitude value of location on  console area. We are successfully getting  current location of device/user.
We can stop location update service any time by using 'stopUpdatingLocation' method. It will be better to stop location service after getting current location. add following  line of code inside of 'didUpdateLocations' method

[locationManager stopUpdatingLocation];

But the problem is, value of location in form of latitude and longitude and it is not in human readable address. Lets convert the coordinate value in human readable address.

CLGeocoder class provide service for convert coordinate to human readable address. By specify the latitude and longitude of a given location, you can use CLGeocoder to find a user-readable address.

Lets create a new method for getting human readable address of coordinate.

-(void) getReadableAddressFrom:(CLLocation *)location{
    CLGeocoder *geocoder = [[CLGeocoder alloc] init];
    [geocoder reverseGeocodeLocation:location completionHandler:^(NSArray *placemarks, NSError *error) {
        NSLog(@"Found placemarks: %@, error: %@", placemarks, error);
        if (error == nil && [placemarks count] > 0) {
            CLPlacemark *placemark = [placemarks lastObject];
            NSString *address = [NSString stringWithFormat:@"%@ %@\n%@ %@\n%@\n%@",placemark.subThoroughfare, placemark.thoroughfare,placemark.postalCode, placemark.locality,placemark.administrativeArea,placemark.country];
            NSLog(@"Address = %@", address);
        } else {
            NSLog(@"%@", error.debugDescription);
        }
    } ];
}

Inside 'didUpdateLocations' method add line of code to call above method.
[self getReadableAddressFrom:location];

Run the code and check the console, you can see address details.

Note :   For running the application on simulator set the default address of simulator.
In the menu bar, select “Debug” -> “Location” for setting the simulator location.

Display a controller on the top of all controller

We have in-build methods to present and navigate a new controller from currently visible controller.
We can use "presentViewController: animated: completion:" method to present a new controller and "pushViewController: animated:" method to push a new controller in navigation controller stack.
But for presenting and navigating a new controller  we must know current visible controller, our presenting and navigation code must be inside the current visible controller file. Suppose our project require to display a controller on notification call, when user receive a notification a controller will present. In this scenario we don't know when the app will receive notification, and at the time of receiving  notification, which controller is on top. So what is the best solution of this problem? first option is write  code inside all classes and call this method on the basis of local notification, when a controller appear its add a observer for present a controller and when its disappear remove that observer. But, is this good option/solution? No, its not a solution of problem. If we accept this approach, than we need to add extra work to controller local notification for present and push controller.  Instead of accepting first approach we will find the current visible controller and present new controller from any where of the application and no need to write same code again and again in side all classes.

In this blog post i am going to find current visible controller and present a new controller.
Lets start,

Go to your project and add new category for UIWindow.
Inside .h file add following methods

- (UIViewController *)visibleViewController;
+ (UIViewController *) getVisibleViewControllerFrom:(UIViewController *) vc;

Now switch to .m file and define methods

- (UIViewController *)visibleViewController {
    UIViewController *rootViewController = self.rootViewController;
    return [UIWindow getVisibleViewControllerFrom:rootViewController];
}

+ (UIViewController *) getVisibleViewControllerFrom:(UIViewController *) vc {
    if ([vc isKindOfClass:[UINavigationController class]]) {
        return [UIWindow getVisibleViewControllerFrom:[((UINavigationController *) vc) visibleViewController]];
    } else if ([vc isKindOfClass:[UITabBarController class]]) {
        return [UIWindow getVisibleViewControllerFrom:[((UITabBarController *) vc) selectedViewController]];
    } else {
        if (vc.presentedViewController) {
            return [UIWindow getVisibleViewControllerFrom:vc.presentedViewController];
        } else {
            return vc;
        }
    }
}
 //--------
In the first method, we are not doing any thing, just we are calling the second method with root controller of window.
In the second method,    we are checking the kind of controller(is a kind of UINavigationController, UITabBarController, presentedViewContrller) and returning top of the controller.

Go to ViewController.m file and import UIWindow category class
 and add below method

-(void) displayFullScreenMessage{
//create a instance of controller
    MessageViewController *controller = [[MessageViewController alloc] initWithNibName:@"MessageViewController" bundle:nil];
    //get main window
    UIWindow *mainWindow =  [[UIApplication sharedApplication] keyWindow];
//get current visible controller
    UIViewController *visiblecontroller = [mainWindow visibleViewController];
//present a controller
    [visiblecontroller presentViewController:controller animated:YES completion:nil];
}

Now we have enough code for display a controller on the top of the controller.
Call the above method and display controller.