Question

设置CLLocationManager来解密错误代码，但我收到了一个未声明的标识符“错误”，我已经注释掉了。

为什么Xcode要求我声明'错误'作为标识符？我以为CLLocationManager会读入错误代码并将它们翻译成普通英语？

我在这里缺少什么？

CurrentLocationViewController.m

#import "CurrentLocationViewController.h"

@interface CurrentLocationViewController ()

@end

@implementation CurrentLocationViewController {
    CLLocationManager *_locationManager;
    CLLocation *_location;

    BOOL _updatingLocation;
    NSError *_lastLocationError;
}

-(id)initWithCoder:(NSCoder *)aDecoder
{
    if((self = [super initWithCoder:aDecoder])) {
        _locationManager = [[CLLocationManager alloc] init];
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self updateLabels];
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

-(IBAction)getLocation:(id)sender
{
    [self startLocationManager];
    [self updateLabels];

}

#pragma mark - CLLocationManagerDelegate

-(void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
    NSLog(@"didFailWithError %@", error);
}

-(void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
    CLLocation *newLocation = [locations lastObject];

    if (error.code == kCLErrorLocationUnknown) {  // Use of undeclared identifier 'error'
        return;
    }

    [self stopLocationManager];
    _lastLocationError = error; // Use of undeclared identifier 'error'

       [self updateLabels];
}

-(void)updateLabels
{
    if (_location != nil) {
        self.latitudeLabel.text = [NSString stringWithFormat:@"%.8f", _location.coordinate.latitude];
        self.longitudeLabel.text = [NSString stringWithFormat:@"%.8f", _location.coordinate.longitude];
        self.tagButton.hidden = NO;
        self.messageLabel.text = @"";
    } else {
        self.latitudeLabel.text = @"";
        self.longitudeLabel.text = @"";
        self.addressLabel.text = @"";
        self.tagButton.hidden = YES;

        NSString *statusMessage;
        if (_lastLocationError == nil) {
            if ([_lastLocationError.domain isEqualToString:kCLErrorDomain] && _lastLocationError.code == kCLErrorDenied) {
                statusMessage = @"Location Services Disabled";
            } else {
                statusMessage = @"Error Getting Location";
            }
        } else if (![CLLocationManager locationServicesEnabled]) {
            statusMessage = @"Location Services Disabled";
        } else if (_updatingLocation) {
            statusMessage = @"Searching...";
        } else {
            statusMessage = @"Press the Button to Start";
        }

        self.messageLabel.text = statusMessage;
        }
}

-(void)startLocationManager
{
    if ([CLLocationManager locationServicesEnabled]) {
        _locationManager.delegate = self;
        _locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
        [_locationManager startUpdatingLocation];
        _updatingLocation = YES;
    }
}

-(void)stopLocationManager
{
    if (_updatingLocation) {
        [_locationManager stopUpdatingLocation];
        _locationManager.delegate = nil;
        _updatingLocation = NO;
    }
}

@end

Answer 1

哦，jeez。你是谁，不是吗？

看起来你有2个方法处理一个名为“error”的变量。

第一个是locationManager：didFailWithError：

此方法是位置管理器在检测到错误状态时将调用的方法。

在该方法中，NSError对象作为“错误”传入。如果您想记录/保存您收到的错误，可以在此处进行操作。如果稍后需要，您应该将错误保存到_lastLocationError。在此方法中向用户显示错误也是一个好主意。

尝试引用名为“error”的变量的第二种方法是locationManager：didUpdateLocations：

该方法没有“错误”作为参数。变量名“错误”在这里没有意义。你不会在这里得到错误值，也不应该指望它们。

如果调用了您的locationManager：didFailWithError：方法，则可能永远不会调用您的locationManager：didUpdateLocations：方法，因为位置管理员已经告诉您存在问题并且无法处理您的请求。

CLLocationManager使用未声明的标识符'错误'

1 个答案: