解决方案与向后兼容，不产生Xcode警告:

SEL requestSelector = NSSelectorFromString(@"requestWhenInUseAuthorization");
if ([CLLocationManager authorizationStatus] == kCLAuthorizationStatusNotDetermined &&
  [self.locationManager respondsToSelector:requestSelector]) {
((void (*)(id, SEL))[self.locationManager methodForSelector:requestSelector])(self.locationManager, requestSelector);
  [self.locationManager startUpdatingLocation];
} else {
  [self.locationManager startUpdatingLocation];
}

在Info.plist中设置NSLocationWhenInUseUsageDescription键。

对于iOS版本11.0+: 在Info.plist中设置NSLocationAlwaysAndWhenInUseUsageDescription键。还有另外2把钥匙。

对我来说，问题是CLLocationManagerDelegate类是私有的，这阻止了所有的委托方法被调用。我想这不是很常见的情况，但我想我应该提到它，以防它能帮助到任何人。

添加关键NSLocationWhenInUseUsageDescription或NSLocationAlwaysUsageDescription(后台GPS使用)字符串要求使用GPS在每个信息。Plist从每个目标。 通过运行命令获得许可: (自我initLocationManager: locationManager);

其中“initLocationManager”为:

// asks for GPS authorization on iOS 8
-(void) initLocationManager:(CLLocationManager *) locationManager{

    locationManager = [[CLLocationManager alloc]init];

    if([locationManager respondsToSelector:@selector(requestAlwaysAuthorization)])
        [locationManager requestAlwaysAuthorization];
}

记住，如果键不是在每个信息上。Plist为每个目标，应用程序将不会询问用户。if提供了与iOS 7的兼容性，respondsToSelector:方法保证了未来的兼容性，而不仅仅是解决iOS 7和8的问题。

用于询问位置的旧代码将无法在iOS 8中使用。您可以尝试使用此方法进行位置授权:

- (void)requestAlwaysAuthorization
{
    CLAuthorizationStatus status = [CLLocationManager authorizationStatus];

    // If the status is denied or only granted for when in use, display an alert
    if (status == kCLAuthorizationStatusAuthorizedWhenInUse || status ==        kCLAuthorizationStatusDenied) {
        NSString *title;
        title = (status == kCLAuthorizationStatusDenied) ? @"Location services are off" :   @"Background location is not enabled";
        NSString *message = @"To use background location you must turn on 'Always' in the Location Services Settings";

        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:title
                                                            message:message
                                                           delegate:self
                                                  cancelButtonTitle:@"Cancel"
                                                  otherButtonTitles:@"Settings", nil];
        [alertView show];
    }
    // The user has not enabled any location services. Request background authorization.
    else if (status == kCLAuthorizationStatusNotDetermined) {
        [self.locationManager requestAlwaysAuthorization];
    }
}

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
    if (buttonIndex == 1) {
        // Send the user to the Settings for this app
        NSURL *settingsURL = [NSURL URLWithString:UIApplicationOpenSettingsURLString];
        [[UIApplication sharedApplication] openURL:settingsURL];
    }
}

Swift开发者常犯的一个错误:

首先确保你添加了一个值到plist为NSLocationWhenInUseUsageDescription或NSLocationAlwaysUsageDescription。

如果你仍然没有看到一个窗口弹出要求授权，看看你是否把行var locationManager = CLLocationManager()在你的视图控制器的viewDidLoad方法。如果这样做，那么即使调用locationManager.requestWhenInUseAuthorization()，也不会显示任何内容。这是因为在viewDidLoad执行后，locationManager变量被释放(清除)。

解决方案是在类方法的顶部找到var locationManager = CLLocationManager()行。

在iOS 8中，你需要做两件额外的事情来让定位工作:给你的信息添加一个键。Plist并从位置管理器请求授权，要求它启动

info.plist:

<key>NSLocationUsageDescription</key>
<string>I need location</string>
<key>NSLocationAlwaysUsageDescription</key>
<string>I need location</string>
<key>NSLocationWhenInUseUsageDescription</key>
<string>I need location</string>

将此添加到代码中

if (IS_OS_8_OR_LATER)
{
    [locationmanager requestWhenInUseAuthorization];

    [locationmanager requestAlwaysAuthorization];
}