问题描述
我想从应用程序的其他地方调用方法，以获取在应用程序委托中获取的用户位置。从另一个视图控制器调用 CLLocation * getCurLoc = [AppDelegate getCurrentLocation]; 时，不会返回任何内容。
I want to call a method from elsewhere in the app to get the user's location that was obtained in the app delegate. When calling CLLocation *getCurLoc = [AppDelegate getCurrentLocation]; from another view controller, nothing is returned.
应用程序代表是，
@synthesize locationManager;
CLLocation *location;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{
locationManager = [[CLLocationManager alloc]init];
locationManager.delegate = self;
locationManager.desiredAccuracy=kCLLocationAccuracyKilometer;
[locationManager startUpdatingLocation];
return YES;
}
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations{
[locations lastObject];
[manager stopUpdatingLocation];
CLLocation *location = [locations lastObject];
}
+(CLLocation *)getCurrentLocation{
return location;
}
将其更改为具有 - 的实例方法无效。应该将位置做成一个实例吗？代理人是否应该成为一个实例，还是有更好的方式从其他地方访问？
Changing it to an instance method with a "-" didn't work. Should "location" be made into an instance? Should the delegate be made into an instance, or is there a better way to access it from elsewhere?
推荐答案
是以一种与您的方法相一致的方式解决此问题的有效快捷方式 - 将位置存储在 appDelegate 。
Martin's answer is an effective quick&dirty way of solving this problem in a way that is consistent with your approach - storing the location in appDelegate.
如果您想进一步了解，您可能需要考虑实现一个特定的对象来保存数据 - 数据模型。在应用程序委托中存储数据是一种不好的做法 - 它不是那里的（尽管它在样本或小应用程序中工作得很好）。
If you want to take a step further you might want to consider implementing a special object that would hold the data - the data model. It is considered a bad practice to store data in application delegate - it is not what it is there for (though it works perfectly fine in sample or small applications).
你可以这样做：
DataModel.h
#import <Foundation/Foundation.h>
@interface DataModel : NSObject
@property (strong) CLLocation *location;
+ (DataModel *)sharedModel;
@end
DataModel.m / p>
DataModel.m
#import "DataModel.h"
@class CLLocation;
@implementation DataModel
- (id) init
{
self = [super init];
if (self)
{
_location = nil;
}
return self;
}
+ (DataModel *)sharedModel
{
static DataModel *_sharedModel = nil;
static dispatch_once_t onceSecurePredicate;
dispatch_once(&onceSecurePredicate,^
{
_sharedModel = [[self alloc] init];
});
return _sharedModel;
}
@end
然后您需要 #importDataModel.h无论你需要什么。您将更改您的 didUpdateLocations：到：
You would then need to #import "DataModel.h" wherever you need it. You would change your didUpdateLocations: to:
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
[locations lastObject];
[manager stopUpdatingLocation];
[DataModel sharedInstance].location = [locations lastObject];
}
从代码中的任何地方，您可以通过 [DataModel sharedInstance] .location 。
And from anywhere in the code you could get this location simply by [DataModel sharedInstance].location.
编辑
对于一个非常简单的应用程序，这种方法可能看起来像一个过度的杀手。但是一旦你的应用程序成长，它肯定会付出代价。
For a very simple app this approach might look as an overkill. But as soon as your app grows it surely pays off to use it.
这种类/对象/单例是保存你的应用程序所需的所有数据（固定的和临时）。所以所有的数据源可以很好地利用它。简而言之：它使您能够轻松地遵循模型视图控制器指南。
This kind of class/object/singleton is ment to hold all the data your app needs (fixed and temporary). So all the data sources can make a good use of it. In short: it enables you to easily follow the model-view-controller guidelines.
你当然使用另一个类/对象/单例来保存临时数据 - 它取决于您的数据结构的复杂性。
You cold of course use another class/object/singleton to hold the temporary data - it depends on the complexity of your data-structure.
您不必具体初始化此类对象。第一次引用时初始化它。这就是为什么 dispatch_once 。它确保存在此共享对象的唯一一个实例：
You don't have to specifically initialize this kind of object. It is initialized the first time you reference it. That is why dispatch_once is there for. It makes sure that there is one and only one instance of this shared object present: http://stackoverflow.com/a/9119089/653513
这个 [DataModel sharedInstance] 的单个实例将一直保留在您的应用程序终止之前
And this one single instance of [DataModel sharedInstance] will remain there until your app is terminated.
Apple为 [NSUserDefaults standardDefaults]，[UIApplication sharedApplicaton] 使用类似的方法。
Apple uses similar approach for [NSUserDefaults standardDefaults], [UIApplication sharedApplicaton] for example.
我倾向于将 #importDataModel.h放入我的项目 Prefix.pch 所以我不必每次使用它导入它（它被用于所有的应用程序）。
I tend to put the #import "DataModel.h" into my projects Prefix.pch so I don't have to import it every single time I use it (it is used trough all the app).
PROS：
- 整个应用程序中的数据可用
- 代码可重用性
- MVC结构
- 代码更易读
PROS:- data accesible throughout the app- code reusability- MVC structure- code is more readable
CONS：
- 我找不到一个。除了 dispatch_once（& onceSecurePredicate，^ ... 可能会在头几秒内混淆一个。
CONS:- I couldn't really find one. Except that the dispatch_once(&onceSecurePredicate,^... might confuse one for the first couple of seconds.
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