Question

    - (NSString *) geocodeAddressFromCoordinate:(CLLocationCoordinate2D)coordinate
    {
        CLLocation *location = [[CLLocation alloc]initWithLatitude:coordinate.latitude longitude:coordinate.longitude];
        __block NSMutableString * address = [NSMutableString string];  
        geocoder = [[CLGeocoder alloc]init];
        [geocoder reverseGeocodeLocation:location completionHandler:^(NSArray *placemarks, NSError *error) 
         {
             if (error) {     
                 NSLog(@"%@", [error localizedDescription]);
                 UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"No results were found" message:@"Try another search" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:nil, nil];
                 alert.show;
                 return;
             }
             if ([placemarks count]>0) 
             {   
                 NSLog([placemarks description]);
                 CLPlacemark *placemark = [placemarks objectAtIndex:0];
                 NSLog(placemark.locality);
//This line makes an error
                 [address initWithString:placemark.locality];**
             }
         }];
        return address;
    }

发生以下运行时错误：

*由于未捕获的异常'NSInvalidArgumentException'而终止应用程序，原因：'* 初始化方法 -initWithCharactersNoCopy：length：freeWhenDone：无法发送到类__NSCFString的抽象对象：创建一个具体的实例！'

Answer 1

你不应该在没有匹配的alloc的情况下调用'initWithString：'。看起来更像你想要的是[address setString:placemark.locality]

Answer 2

您已使用此行address初始化[NSMutableString string];，因此您对[address initWithString:placemark.locality];的调用正在尝试初始化已初始化的对象。

改变这个：

[address initWithString:placemark.locality];

要：

[address setString:placemark.locality];

NSString Class Reference
NSMutableString Class Reference

Answer 3

[address initWithString:placemark.locality];

应该更像是：

address = placemark.locality;

或

[address appendString:placemark.locality];

取决于你想要完成什么。

Answer 4

此时，您的字符串已经初始化，[NSMutableString string]是一个方便的方法，它必须返回[[[NSMutableString alloc] init] autorelease]。您正在尝试重新启动一个已经存在的对象，这很糟糕。

将该行更改为[address appendString：placemark.locality];

在块中分配NSString变量时出错

4 个答案: