How to call a variable from another class - ios

Question

First off, do you guys know of any good tutorial sites or books to learn how to code for iOS6?
Now to the problem at hand, I have an AppDelegate class and a ViewController class.
I am using the AppDelegate class to find my current location and save it as an NSString.
I have a label in my ViewController class where I want to display my location.
In java I would usually just do something like this
label.text = AppDelegate.myLocationString;
But I am fairly new to objective c and I don't know how to do the equivalent. To be honest I'm not even sure if I am taking the correct approach for this language. Is there another way to approach this problem in objective c?
I've tried searching around for how to do it but I'm not even sure that I'm phrasing my searches correctly so I don't know if I'm searching in the right direction.
Any help that could be offered would be very much appreciated
My code as it is now:
AppDelegate.h
#import <UIKit/UIKit.h>
#import CoreLocation/CoreLocation.h
#class BIDViewController;
#interface BIDAppDelegate : UIResponder <UIApplicationDelegate, CLLocationManagerDelegate>
#property (strong, nonatomic) UIWindow *window;
#property (strong, nonatomic) BIDViewController *viewController;
#property (strong, nonatomic) CLLocationManager *locationManager;
#property (strong, nonatomic) NSString *myPosition;
#end
LocationManager class from AppDelegate.m
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
NSDate *eventDate = newLocation.timestamp;
NSTimeInterval howRecent = [eventDate timeIntervalSinceNow];
if (abs(howRecent) < 15) {
//if it is within the last 15 seconds, use it. Else do nothing.
if (newLocation.horizontalAccuracy < 35.0) {
//location seems pretty accurate so we will use it
NSLog(#"latitude: %+.6f, longitude: %+.6f\n", newLocation.coordinate.latitude, newLocation.coordinate.longitude);
NSLog(#"Horizontal accuracy: %f", newLocation.horizontalAccuracy);
int latDegrees = newLocation.coordinate.latitude;
int lonDegrees = newLocation.coordinate.longitude;
double latDecimal = fabs(newLocation.coordinate.latitude - latDegrees);
double lonDecimal = fabs(newLocation.coordinate.longitude - lonDegrees);
int latMinutes = latDecimal * 60;
int lonMinutes = lonDecimal * 60;
double latSeconds = ((latDecimal * 3600) - (latMinutes * 60));
double lonSeconds = ((lonDecimal * 3600) - (lonMinutes * 60));
_myPosition = [NSString stringWithFormat:#"Lat: %d, %d, %1.4f, Lon: %d, %d, %1.4f", latDegrees, latMinutes, latSeconds, lonDegrees, lonMinutes, lonSeconds];
}
}
}
ViewController.h
#import <UIKit/UIKit.h>
#interface BIDViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *positionLabel;
#end
ViewController.m
#import "BIDViewController.h"
#import "BIDAppDelegate.h"
#interface BIDViewController ()
#end
#implementation BIDViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
//I have tried setting the label's text here but to no avail so far, I have been
//able to set it as "blah" with the following line:
//
// positionLabel.text = #"blah";
//
//and I have tried things such as the following to populate the label with the
//myPosition variable:
//
// positionLabel.text = _myPosition;
// or
// positionLabel.text = AppDelegate._myPosition;
}
- (void)viewDidUnload
{
[self setPositionLabel:nil];
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
#end

Answer 1

To reference the App Delegate from your view controller, first import its definition (which you've ready done):
#import "BIDAppDelegate.h"
and then in code get the delegate:
BIDAppDelegate *appDelegate = (BIDAppDelegate *)[[UIApplication sharedApplication] delegate];
and then get the location from the delegate:
CLLocation *location = appDelegate.locationManager.location;
and then call whatever method you like on the location object:
NSString *descr = location.description;
Or get the pre-calculated position with:
NSString *position = appDelegate.myPosition;

Answer 2

In your ViewController
BIDAppDelegate *appDelegate = (BIDAppDelegate *)[UIApplication sharedApplication].delegate;
[positionLabel setText:appDelegate.myPosition];

Answer 3

How to call a variable from another class?
Assume you are in ClassB
ClassA *aObj=... ; //create an object of ClassA
aObj.propertyName=...;//set the property or ivar
NSString *string=aObj.propertyName;//retrieve it
do you guys know of any good tutorial sites or books to learn how to
code for iOS6?
http://www.lynda.com/Apple-training-tutorials/106-0.html
http://www.raywenderlich.com/tutorials