首先，你们知道有什么好的教程网站或书籍可以学习如何为 iOS6 编写代码吗？

现在解决手头的问题，我有一个 AppDelegate 类和一个 ViewController 类。

我正在使用 AppDelegate 类来查找我的当前位置并将其保存为 NSString。

我的 ViewController 类中有一个标签，我想在其中显示我的位置。

在java中我通常会做这样的事情

label.text = AppDelegate.myLocationString;

但我对 objective-c 还很陌生，我不知道如何做同样的事情。老实说，我什至不确定我是否为这种语言采用了正确的方法。有没有另一种方法可以解决 objective-c 中的这个问题？

我已经尝试四处寻找如何去做，但我什至不确定我的搜索措辞是否正确，所以我不知道我是否在正确的方向上搜索。

如能提供任何帮助，我们将不胜感激

我现在的代码:

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

AppDelegate.m 中的 LocationManager 类

- (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

最佳答案

要从您的 View Controller 引用 App Delegate，首先导入它的定义(您已准备好):

#import "BIDAppDelegate.h"

然后在代码中获取委托(delegate):

BIDAppDelegate *appDelegate = (BIDAppDelegate *)[[UIApplication sharedApplication] delegate];

然后从委托(delegate)处获取位置:

CLLocation *location = appDelegate.locationManager.location;

然后在位置对象上调用您喜欢的任何方法:

NSString *descr = location.description;

或者获取预先计算好的位置:

NSString *position = appDelegate.myPosition;

关于ios - 如何从另一个类调用变量，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/15025981/