[NSMutableURLRequest released]: message sent to deallocated instance

My app is calling the rqst_run method below in didViewLoad method but I've an error. Debugger reports the following error:

[NSMutableURLRequest released]: message sent to deallocated instance

I don't know where this variable get released

Declared in header file (interface section):

NSMutableString        *rqst_error;
NSMutableData      *rqst_data;
NSMutableDictionary    *listing_items;

and I defined this method in implementation:

- (void)rqst_run
{
    rqst_data = [[NSMutableData data] retain];
    NSMutableURLRequest *http_request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://www.feedserver.com/request/"]];
    [http_request setHTTPMethod:@"POST"];
    NSString *post_data = [[NSString alloc] initwithFormat:@"param1=%@&param2=%@&param3=%@",rqst_param1,rqst_param2,rqst_param3];
    [http_request setHTTPBody:[post_data dataUsingEncoding:NSUTF8StringEncoding]];
    rqst_finished = NO;
    [post_data release];
    NSURLConnection *http_connection = [[NSURLConnection alloc] initWithRequest:http_request];
    [http_request release];

    if(http_connection)
    {
        [[NSRunLoop currentRunLoop] runMode:N开发者_运维百科SDefaultRunLoopMode beforeDate:[NSDate distantFuture]];

        if([rqst_data length]>0)
        {
            NSString *rqst_data_str = [[NSString alloc] rqst_data encoding:NSUTF8StringEncoding];   
            SBJsonParser *json_parser = [[SBJsonParse alloc] init];
            id feed = [json_parser objectWithString:rqst_data_str error:nil];
            listing_items = (NSMutableDictionary *)feed;
            [json_parser release];
            [rqst_data_str release];
        }   
        else
        {
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Feed" message:@"No data returned" delegate:self cancemButtonTitle:@"Ok" otherButtonTitles:nil, nil];
            [alert show];
            [alert release];
        }
   }
   else
   {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Connection Problem" message:@"Connection to server failed" delegate:self cancemButtonTitle:@"Ok" otherButtonTitles:nil, nil];
        [alert show];
        [alert release];
   }
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [rqst_data setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [rqst_data appendData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    [rqst_data release];
    [connection release];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    [rqst_data release];
    [connection release];
    rqst_finished = YES;
}

Your initialization

NSMutableURLRequest *http_request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://www.feedserver.com/request/"]];

is a convenience constructor that has a built-in autorelease for the object you are initializing using the constructor. So by calling

[http_request release];

you are trying to release something that is auto-released. In other words, you are over-releasing.

You should only call release on objects that you allocate using the keywords,

"New", "Alloc", "Copy". or use "retain"

Line [http_request release]; is unnecessary as your object is autoreleased.

For creation of your NSMutableURLRequest you used method which returns aurora eased instance and you not responsible for it's release. If you use methods which require you perform -alloc, -copy, -retain than you responsible for releasing this instance.