Question: Is there a system indipendent way of detecting when an `IOException` is related to a "no space left on device" error? `IOException` has no methods. Shall I treat it as a generic I/O error without explaining the user why? Or should I simply display the exception message string to the user (which might be too techinical)?

Answer: 
Change 

```
NSURL *baseURL = [NSURL URLWithString:@"http://128.199.186.47:8080/DenkoStationServer-1/denkoservice"];

```

to

```
NSURL *baseURL = [NSURL URLWithString:@"http://128.199.186.47:8080/DenkoStationServer-1/denkoservice/price"];

```

and 

```
RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:mapping method:RKRequestMethodGET pathPattern:nil keyPath:@"price" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

```

to

```
RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:mapping method:RKRequestMethodGET pathPattern:nil keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];

```
Status 404 is most definitely not a server error. You should really go just to Wikipedia, for example, and read up what all the http status codes mean, or you will be lost forever. 

For starters, it is not an error. It is a status. It doesn't say something went wrong, it informs you what happened. 404 means: Resource not found. You asked for a resource, the server fully understood what you are looking for, and it found that whatever you are looking for just isn't there. If the data was there, it would have found it, but it wasn't there. There's not a hint of a server error. 

Now obviously you might have made a mistake, and you are not looking for what you wanted to look for. That's your fault.