locationManager 避免标签中的（空）字符串

Question

我有一些代码可以找到用户位置并将其返回到标签中。在某些情况下，subAdministrativeArea 或通道不可用，我想修改我的字符串，使其不显示 (null)。我尝试了一些 if 来检查这一点，但如果 (null) 不止一个，则会出现问题。有人对此有任何想法吗？

这是我当前需要修改的代码，以检测地标对象是否等于 null：

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
        CLLocation *currentLocation = newLocation;
        [location stopUpdatingLocation];

        [geocoder reverseGeocodeLocation:currentLocation completionHandler:^(NSArray *placemarks, NSError *error) {
        if (error == nil && [placemarks count] > 0) {
            placemark = [placemarks lastObject];

            countryDetected = placemark.ISOcountryCode;
            placeLabel.text = [NSString stringWithFormat:@"%@, %@, %@, %@, %@ %@", placemark.country, placemark.subAdministrativeArea, placemark.subLocality, placemark.postalCode, placemark.thoroughfare, placemark.subThoroughfare];
            userPlace = [NSString stringWithFormat:@"%@, %@, %@, %@, %@ %@", placemark.country, placemark.subAdministrativeArea, placemark.subLocality, placemark.postalCode, placemark.thoroughfare, placemark.subThoroughfare];

        } else {
            NSLog(@"%@", error.debugDescription);
        }
    } ];
}

Answer 1

试试这个..如果placemark.subAdministrativeArea是nil，那么你可以在if条件中编写你自己的字符串，否则将placemark.subAdministrativeArea的值设置为字符串变量并将其分配给UILable ...

更新：

NSMutableString *strLblTexts = [[NSMutableString alloc] init];
if (placemark.country != nil) {
        [strLblTexts appendString:placemark.country];
}
if (placemark.subAdministrativeArea != nil) {
        if ([strLblTexts isEqualToString:@""]||[strLblTexts isEqual:nil]) {
        [strLblTexts appendString:placemark.subAdministrativeArea];
    }
    else{
        NSString *strtemp=[NSString stringWithFormat:@",%@",placemark.subAdministrativeArea];

        NSLog(@">>>>>>>>>>>>> str temp :%@", strtemp);
        [strLblTexts appendString:strtemp];
    }
}
if (placemark.subLocality != nil) {
        if ([strLblTexts isEqualToString:@""]||[strLblTexts isEqual:nil]) {
        [strLblTexts appendString:placemark.subLocality];
    }
    else{
        NSString *strtemp=[NSString stringWithFormat:@",%@",placemark.subLocality];

        NSLog(@">>>>>>>>>>>>> str temp :%@", strtemp);
        [strLblTexts appendString:strtemp];
    }
}

像另一个 3 字段一样做，最后将该值设置为UILable，如下所示...

placeLabel.text = strLblTexts;

Answer 2

两种选择：

1) 使用NSMutableString 并且只附加非零值

2) 更新您当前的解决方案，使每个参数如下：

placemark.country ? placemark.country : @"", placemark.subAdministrativeArea ? placemark.subAdministrativeArea : @"", ...

更新：我没有注意到原始问题中的逗号。由于那些在那里，您最好的选择是选项 1：

NSMutableString *label = [NSMutableString string];
if (placemark.country) {
    [label appendString:placemark.country];
}
if (placemark.subAdministrativeArea) {
    if (label.length) {
        [label appendString:@", "];
    }
    [label appendString:placemark.subAdministrativeArea];
}
// and the rest