iphone从坐标解析地址 注意事项

调用解析委托

        MKReverseGeocoder *geocoder = [[MKReverseGeocoder alloc] initWithCoordinate:coo];
        geocoder.delegate = self;
        [geocoder start]; //调用委托 是异步调用 本函数结束后才会调用委托。

如果解析成功调用：

-(void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFindPlacemark:(MKPlacemark *)placemark {
    NSString *sss = [placemark.addressDictionary objectForKey:@"FormatterAddressLines"];
    if (sss) {
        NSLog(@"sss = %@", sss);
    } else {
        //...
    }
    
	NSLog(@"countryCode=%@",placemark.countryCode);  
	NSLog(@"country=%@",placemark.country);  
    NSLog(@"administrativeArea=%@",placemark.administrativeArea);  
	NSLog(@"subAdministrativeArea=%@",placemark.subAdministrativeArea);  
	NSLog(@"locality=%@",placemark.locality);  
	NSLog(@"subLocality=%@",placemark.subLocality);   
	NSLog(@"thoroughfare=%@",placemark.thoroughfare);  
	NSLog(@"subThoroughfare=%@",placemark.subThoroughfare);  
	NSLog(@"postalCode=%@",placemark.postalCode);  
    
	NSString  *  addressResult = @"";  
	NSString  *  beijin=@"北京市";  
	NSString  *  shanghai=@"上海市";  
	NSString  *  tianjin=@"天津市";  
	NSString  *  chongqin=@"重庆市";  
    if ([placemark.administrativeArea isEqualToString:beijin] ||  
        [placemark.administrativeArea isEqualToString:shanghai] ||  
        [placemark.administrativeArea isEqualToString:tianjin] ||  
        [placemark.administrativeArea isEqualToString:chongqin]   )   {  
            addressResult= placemark.locality;  
    } else {  
        //如果不是中国，那么加上国家名称   
        if(placemark.countryCode != @"CN") {  
            addressResult = [addressResult stringByAppendingString:placemark.country];  
            addressResult = [addressResult stringByAppendingString:@" "];  
        }  

        if([placemark.administrativeArea length] > 0) {  
            addressResult= [addressResult stringByAppendingString:@" "];  
            addressResult= [addressResult stringByAppendingString:placemark.administrativeArea];  

            //如果不是中国，那么各个段直接加上空格   
            if(placemark.countryCode != @"CN")  
            {  
                addressResult = [addressResult stringByAppendingString:@" "];  
            }  
        }  

        if([placemark.locality length] > 0) {  
            addressResult = [addressResult stringByAppendingString:placemark.locality];  

            //如果不是中国，那么各个段直接加上空格   
            if(placemark.countryCode != @"CN") {  
                addressResult = [addressResult stringByAppendingString:@" "];  
            }  
        }  
    }  

    if ([placemark.subLocality length]>0) {  
        addressResult = [addressResult stringByAppendingString:placemark.subLocality];  

        //如果不是中国，那么各个段直接加上空格   
        if(placemark.countryCode != @"CN") {  
            addressResult = [addressResult stringByAppendingString:@" "];  
        }  
    }  
    if ([placemark.thoroughfare  length]>0) {  
        addressResult = [addressResult stringByAppendingString:placemark.thoroughfare];  

        //如果不是中国，那么各个段直接加上空格   
        if(placemark.countryCode != @"CN") {  
            addressResult = [addressResult stringByAppendingString:@" "];  
        }  
    }  

    if ([placemark.subThoroughfare  length] > 0) {  
        addressResult= [addressResult stringByAppendingString:@" "];  
        addressResult = [addressResult stringByAppendingString:placemark.subThoroughfare];  
    }
    
    NSLog(@" addressResult= %@",addressResult);
    

    self.userLongPressAddress = addressResult;
    NSLog(@"userLongPressAddress = %@", userLongPressAddress);
    
    //因为解析是异步的，所以为了保证大头针再解析后生成，逻辑放到解析之后。
    MapAnnotation *ann = [[MapAnnotation alloc]initWitchCoordinate:geocoder.coordinate];
    ann.title = @"已放置的大头针";
    NSLog(@"解析出的地址:%@", userLongPressAddress);
    ann.subtitle = userLongPressAddress;
    [myMapView addAnnotation:ann];
    [ann release]; //解析出来的地址放到大头针的子标题
    
    return;
}

如果解析失败 调用

-(void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error {
    NSLog(@"逆向地理解析失败");
    self.userLongPressAddress = @"地址解析失败!!!";
    
    //因为解析是异步的，所以为了保证大头针再解析后生成，逻辑放到解析之后。
    MapAnnotation *ann = [[MapAnnotation alloc]initWitchCoordinate:geocoder.coordinate];
    ann.title = @"已放置的大头针";
    NSLog(@"解析出的地址:%@", userLongPressAddress);
    ann.subtitle = userLongPressAddress;
    [myMapView addAnnotation:ann];
    [ann release];
    
    [geocoder release];
}

代码参考：http://blog.youkuaiyun.com/tangaowen/article/details/6527907 谢谢这位博主。
注意事项：逆向地址解析是异步的，当 start接口调用的时候，解析函数并不马上运行，所以如果在调用解析的逻辑后面立刻取解析结果，是肯定会取到错误值的。

取解析结果的操作一定要在解析函数执行结束才能使用。

至于解析什么时候执行，就要看ios自己的线程调度算法了，一般来说十几毫秒会切换一次线程，或者一个线程执行完毕就会执行其他优先级高的线程，作为使用者，不需要精确地知道什么时候，只要在确定解析执行之后再添加自己的逻辑就行了。

另外，解析操作大部分时候是失败的！所以只能作为辅助业务，目前还不可能作为一个精确度高的功能点。