ios - 为什么我的第一个回复是空的？

Question

我有一个 Location.m 模型，我用它来获取纬度和经度。当我拥有这些时，我会调用在我的 Foursquare.m 模型中实现的委托(delegate)方法。

Location.h 看起来像这样:

@class Location;

@protocol LocationDelegate <NSObject>
- (void)location:(Location *)loc didFinishFindingLocation:(CLLocation *)location;
@end

@interface Location : NSObject <CLLocationManagerDelegate>

@property (nonatomic, weak) id <LocationDelegate> delegate;    
- (void)startLocationManager;

@end

位置.m:

@implementation Location
{
    CLLocationManager *_locationManager;
    BOOL _locationIsUpdated;
}

- (void)startLocationManager
{
    NSLog(@"In startLocationManager");
    _locationManager = [[CLLocationManager alloc] init];
    _locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
    _locationManager.delegate = self;
    _locationIsUpdated = NO;
    [_locationManager startUpdatingLocation];
}

#pragma mark - LocationManager Delegates

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
    if (locations && _locationIsUpdated == NO) {
        self.location = [locations lastObject];
        NSLog(@"%@", _location);
        _locationIsUpdated = YES;
        [self.delegate location:self didFinishFindingLocation:self.location];
    }

}

@end

当从 Foursquare 模型调用委托(delegate)方法时，我将 NSLog 的响应输出到一个数组中(称为 self.dataResponse)。它总是首先输出 (null)，然后是所有的 JSON。为什么会这样？如果我直接 NSLog out dataDictionary(见下面的代码)，JSON 输出显示错误代码:400 并且不打印任何内容。打印完所有内容后几毫秒，似乎工作正常...

这是一张图片:当我记录 dataDictionary

这是在 Foursquare.m 中实现的委托(delegate)方法:

- (void)location:(Location *)loc didFinishFindingLocation:(CLLocation *)location
{
    loc.delegate = self;

    self.resultFromResponse = [[NSMutableArray alloc] init];
    NSString *search = [NSString stringWithFormat:@"https://api.foursquare.com/v2/venues/search?ll=%f,%f&radius=2000&categoryId=4d4b7105d754a06374d81259&client_id=%@&client_secret=%@&v=%@", location.coordinate.latitude, location.coordinate.longitude, kFourdquareAPIKey, fFoursquareSecret, [Foursquare getCurrentDate]];

    NSURL *url = [NSURL URLWithString:search];
    NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:config];

    NSURLSessionDataTask *task = [session dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        NSDictionary *dataDictionary = (NSDictionary *)[NSJSONSerialization JSONObjectWithData:data options:0 error:&error];
        if (!error) {
            self.dataResponse = dataDictionary[@"response"][@"venues"];
            NSLog(@"%@", self.dataResponse);
            for (NSDictionary *venue in self.dataResponse) {
                FSDataFromJSON *data = [[FSDataFromJSON alloc] init];
                data.name = venue[@"name"];
                data.phone = venue[@"phone"];
                data.location = venue[@"location"];
                [self.resultFromResponse addObject:data];
            }
            //[[NSNotificationCenter defaultCenter] postNotificationName:@"JSONRequestFinishedLoading" object:nil];
        } else {
            NSLog(@"%@", error.description);
        }
    }];

    [task resume];
}

最后，这些模型在我的 MainViewController 中启动:

 _location = [[Location alloc] init];
    [_location startLocationManager];

    _foursquare = [[Foursquare alloc] init];
    [_foursquare location:_location didFinishFindingLocation:_location.location];

Answer 1

据我所知，您问题中的最后一行代码可能是问题所在:

[_foursquare location:_location didFinishFindingLocation:_location.location];

您不应该显式调用您的委托(delegate)方法(在设置位置之前)。相反，您应该等待 CLLocation 回调将其启动。

其他想法:

• 如果 Location 类有一个 .location 属性，我认为这是令人困惑的。

• Location.m 不是模型，它是包含类实现的文件。我会说 Location 类是一个模型。

• 您可以将委托(delegate)方法简化为 didFindLocation:(Location *)location，因为您可以在方法中将 CLLocation 作为 location.location .

• 房地产最重要的三个因素是什么？ location.location.location !