Question

我有一个前向gecodoing方法。我想将结果保存在变量中，以便我可以在viewDidLoad中使用它。

- (void)getGeoInformations
{
    NSLog(@"Begin");
    __block NSString *returnAddress = @"";

    CLGeocoder *geoCoder = [[CLGeocoder alloc] init];
    [geoCoder geocodeAddressString:@"Isartor" completionHandler:^(NSArray* placemarks, NSError* error){
        if(error) {
            NSLog(@"Error");
            return;
        }
            CLPlacemark *placemark = [placemarks lastObject];
        NSArray *lines = placemark.addressDictionary[ @"FormattedAddressLines"];
        //addressString = [lines componentsJoinedByString:@"\n"];
        NSString *str_latitude = [NSString stringWithFormat: @"%f", placemark.location.coordinate.latitude];
        NSString *str_longitude = [NSString stringWithFormat: @"%f", placemark.location.coordinate.longitude];
        returnAddress = [NSString stringWithFormat:@" %@, %@, %@",
                        lines,
                        str_latitude, str_longitude];
        NSLog(returnAddress);
        NSLog(@"Ende");
        [self loadGeoInformations:returnAddress];
    }];
}

经过www研究，我知道，这是一个异步调用，我必须使用回调。

-(void)loadGeoInformations:(NSString*)returnAddress {

}

我已尝试过几件事来存储 returnAddress ，但没有成功..

如何保存结果？

谢谢你。

Answer 1

使用实例变量。在.m文件的顶部声明实例var NSString：

@interface YourFileHere {
    NSString *_returnAddress;
}

然后，稍后当您调用传递地址的方法时，可以将其保存到实例变量中以便以后使用。

-(void)loadGeoInformations:(NSString*)returnAddress {
    _returnAddress = returnAddress;
}

以下是包含日志和评论的完整代码，其中显示了事情将如何发生：

- (void)viewDidLoad {
    [super viewDidLoad];

    // #1 - This is called first
    NSLog(@"Calling getGeoInformations in view did load.");
    [self getGeoInformations];
}

- (void)getGeoInformations {
    // #2 - This will be called during view did load.
    NSLog(@"Inside getGeoInformations");
    CLGeocoder *geoCoder = [[CLGeocoder alloc] init];
    [geoCoder geocodeAddressString:@"Isartor" completionHandler:^(NSArray* placemarks, NSError* error){
        // This is called later, at some point after view did load is called.
        NSLog(@"Inside completionHandler.");

        if(error) {
            NSLog(@"Error");
            return;
        }

        CLPlacemark *placemark = [placemarks lastObject];
        NSArray *lines = placemark.addressDictionary[@"FormattedAddressLines"];
        NSString *str_latitude = [NSString stringWithFormat: @"%f", placemark.location.coordinate.latitude];
        NSString *str_longitude = [NSString stringWithFormat: @"%f", placemark.location.coordinate.longitude];
        NSString *returnAddress = [NSString stringWithFormat:@" %@, %@, %@", lines, str_latitude, str_longitude];

        // #4 - Now we have the return address, so we can pass it to the load method.
        [self loadGeoInformations:returnAddress];
    }];

    // #3 - Anything here will be called during view did load, but BEFORE the completion handler of the geocoding process is called.
    NSLog(@"This is called third.");
}

- (void)loadGeoInformations:(NSString*)returnAddress {
    // #5 - this will be called last, some time after view did load is done.
    _returnAddress = returnAddress;
    NSLog(@"Inside load geo informations with return address: %@", _returnAddress);
}

geocodeAddressString：保存回调无效的结果

1 个答案: