Why my application crash on applicationDidEnterBackground?

I have a static method called writeToServer that is called when application enter in background mode.

in my AppDelegate.m:

- (void)applicationDidEnterBackground:(UIApplication *) application {
    [LogZone writeToServer];
    NSLog(@"Log sended to server. Done.");
}

in my LogZone.m:

+ (void) writeToServer {
    NSString *qStr = [[NSString alloc]
        initWithFormat:@"%@?ip=%@&uid=%@&platform=%@&model=%@&lat=%@&lon=%@",
            LOG_SERVER_URL,
            _LOG_IP, _LOG_UID, _LOG_PLAT, _LOG_MOD, _LOG_LAT, _LOG_LON];

    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:qStr]];    
    [request setHTTPMethod: @"POST"];
    [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
}

Uppercase vars are static strings created in this way:

.h

extern NSString* _LOG_UID;

.m开发者_如何学JAVA

NSString* _LOG_UID = @"-1";

When I enter in background mode it crash with this "classic" error:

* -[CFString respondsToSelector:]: message sent to deallocated instance 0x6a4c800

But why?

I don't release anything!=!

What's wrong?

---

But why? I don't release anything!

Sure, but do you retain the right objects?

Retaining at the right time is every bit as important as not releasing at the wrong time...

---

Why not just use the following:

NSString *qStr = [NSString stringWithFormat:@"%@?ip=%@&uid=%@&platform=%@&model=%@&lat=%@&lon=%@", LOG_SERVER_URL, _LOG_IP, _LOG_UID, _LOG_PLAT, _LOG_MOD, _LOG_LAT, _LOG_LON];