Yet another "message sent to deallocated instance" - iphone

Question

My app crashed (iOS/iPhone) after the execution of the following snippet:
NSHTTPURLResponse *urlResponse = nil;
NSError *error = [[NSError alloc] init];
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&urlResponse error:&error];
NSString *result = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
if ([urlResponse statusCode] ==500 ) {
...
}
} else {
NSLog(#"Response ==> status= %d", [urlResponse statusCode];
}
[result release];
[error release];
The code reached at the else statement, the statusCode is "0" and the code crashes with the
information that [CFError release] was sent to an deallocated instance. I commented out the
line [error release] and the crashed did not happen again. However we introduce a leak here.
What goes wrong with the error variable? Is it being used from sendSynchonousRequest?
What is the optimal way to resolve the problem?

Answer 1

The error object passed to an other method most not be initialized, the method you pass it on to will create the error object if an error accours. Since this method created the error object you are not the owner of that object and you are over releasing the error. The error object is created as autorelease.
Change :
NSError *error = [[NSError alloc] init];
to
NSError *error = nil;
and remove the
[error release];

Answer 2

Its is not necessary create error object. when you set the object to NSURLConnection, it automatic create autorelease error object. thats why your code crash, because there are also error release
try this:
NSHTTPURLResponse *urlResponse = nil;
NSError *error = nil;
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&urlResponse error:&error];
NSString *result = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
if ([urlResponse statusCode] ==500 ) {
...
}
} else {
NSLog(#"Response ==> status= %d", [urlResponse statusCode];
}
[result release];