比较背景中 2 个位置的 2 个城市答案

【问题标题】：Comparing 2 cities from 2 locations in background比较背景中 2 个位置的 2 个城市
【发布时间】：2016-02-21 11:22:03
【问题描述】：

我有一个应用程序，用户保存位置并设置要通知它的半径：1KM、5KM（如果他之前保存的位置并且他在设置的半径内是当前位置，用户将收到通知）和“城市”（如果用户之前保存的位置所在城市与当前所在城市是同一城市，用户将收到通知）。

注意：我使用的是Google Maps iOS SDK。

我有一个名为-sendNotificationIfNeeded 的方法来检查是否发送通知，代码：

-(void)sendNotificationIfNeeded
{    
    if (self.muteEnabled==YES) { //Check if the user muted the app
        NSLog(@"Mute enabled");
        return;
    }

    //Important part:
    if([self checkIfUserInRadiusForLocation:[self.savedLocations objectAtIndex:0]])
    {
        UILocalNotification *notification=[self createNotification];
        [self sendNotification:notification];
    }
}

方法checkIfUserInRadiusForLocation检查savedLocation(CLCircularRegion)的半径并检查用户是否在这个半径内，代码：

-(BOOL)checkIfUserInRadiusForLocation:(SavedLocation*)location
{
    if(location.radiusString isEqualToString:@“1KM”)
    {
        if(location.circularRegion containsCoordinate:self.locationManager.location.coordinate)
        {
            return YES;
        }
    }else if(location.radiusString isEqualToString:@“5KM”)
    {
        if(location.circularRegion containsCoordinate:self.locationManager.location.coordinate)
        {
            return YES;
        }
    //Important part:
    }else if(location.radiusString isEqualToString:@“City”)
    {
        if([self checkIfUserCityIsSameToLocation:location)
        {
            return YES;
        }
    }
    return NO;
}

方法checkIfUserCityIsSameToLocation:查找savedLocation城市和用户所在的城市，并检查它们是否相等（问题出在这里），代码：

-(BOOL)checkIfUserCityIsSameToLocation:(savedLocation*)location
{
    //Checking user's city
    __block NSString *userCity;
    [[GMSGeocoder geocoder]reverseGeocodeCoordinate:self.locationManager.location.coordinate completionHandler:^(GMSReverseGeocodeResponse *response, NSError *error) {
        if (error) {
            NSLog(@"%@",[error description]);
        }
        userCity=[[[response results] firstObject] locality];
    }];
    //Checking savedLocation’s city
    __block NSString *savedLocationCity;
    [[GMSGeocoder geocoder]reverseGeocodeCoordinate:location.circularRegion.center completionHandler:^(GMSReverseGeocodeResponse *response, NSError *error) {
        if (error) {
            NSLog(@"%@",[error description]);
        }
        savedLocationCity=[[[response results] firstObject] locality];

        NSLog(@"");
    }];

    if ([userCity isEqualToString:savedLocationCity]) { //Both string cities are nil
        Return YES;
    }else
    {
        Return No
    }
}

问题是当应用程序到达checkIfUserCityIsSameToLocation: 上的if 状态时，userCity 和savedLocationCity 都为零（因为reverseGeocodeCoordinate: completionHandler: 方法在后台线程上运行）。

我不知道怎么解决，

如果有人能帮我解决这个问题，我会非常感激。

非常感谢！

【问题讨论】：

标签： ios objective-c iphone cocoa-touch google-maps-sdk-ios

【解决方案1】：

这样做：

-(BOOL)checkIfUserInRadiusForLocation:(SavedLocation*)location userCity: (NSString *) userCity locationCity: (NSString *) locationCity
{
    if(location.radiusString isEqualToString:@“1KM”)
    {
      if(location.circularRegion containsCoordinate:self.locationManager.location.coordinate)
      {
        return YES;
      }
    }else if(location.radiusString isEqualToString:@“5KM”)
    {
      if(location.circularRegion containsCoordinate:self.locationManager.location.coordinate)
      {
        return YES;
      }
    //Important part:
    }else if(location.radiusString isEqualToString:@“City”)
    {
      if([userCity isEqual: locationCity])
      {
        return YES;
      }
    }
return NO;
}


-(void)sendNotificationIfNeeded
{    
    if (self.muteEnabled==YES) { //Check if the user muted the app
        NSLog(@"Mute enabled");
        return;
    }
    SavedLocation* location = [self.savedLocations objectAtIndex:0];
    [[GMSGeocoder geocoder]reverseGeocodeCoordinate:self.locationManager.location.coordinate completionHandler:^(GMSReverseGeocodeResponse *response, NSError *error) {
    if (error) {
        NSLog(@"%@",[error description]);
    }
    NSString *userCity=[[[response results] firstObject] locality];
   [[GMSGeocoder geocoder]reverseGeocodeCoordinate:location.circularRegion.center completionHandler:^(GMSReverseGeocodeResponse *response, NSError *error) {
    if (error) {
        NSLog(@"%@",[error description]);
    }
    NSString *savedLocationCity=[[[response results] firstObject] locality];

    if([self checkIfUserInRadiusForLocation:location userCity: userCity locationCity: savedLocationCity])
    {
      UILocalNotification *notification=[self createNotification];
      [self sendNotification:notification];
    }
    }];
  }];
}

【讨论】：