NSMutableData导致内存泄漏

Question

I have a class for connecting with httprequests. I am getting a memory leak for "NSMutableData" altho I am releasing it in "didFailWithError" and in "connectionDidFinishLoading" of the connection object:

- (BOOL)startRequestForURL:(NSURL*)url {

[url retain];


NSMutableURLRequest* urlRequest = [[NSMutableURLRequest alloc] initWithURL:url];
// cache & policy stuff here
[[NSURLCache sharedURLCache] removeAllCachedResponses];
[urlRequest setHTTPMethod:@"POST"];
[urlRequest setHTTPShouldHandleCookies:YES];
NSURLConnection* connectionResponse = [[[NSURLConnection alloc] initWithRequest:urlRequest delegate:self] autorelease];
if (!connectionResponse)
{
    // handle error
    return NO;
} else {
    receivedData = [[NSMutableData data] retain]; // memory leak here!!!
}

[url release];

[urlRequest release];


return YES;}

- (void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error {
UIAlertView *alert =
[[[UIAlertView alloc]
  initWithTitle:NSLocalizedString(@"Connection problem", nil)
  message:NSLocalizedString(@"A connection problem detected. Please check your internet connection and try again.",nil)

  delegate:self
  cancelButtonTitle:NSLocalizedString(@"OK", nil)
  otherButtonTitles:nil, nil]
 autorelease];
[alert show];

[connectionDelegate performSelector:failedAction withObject:error];
[receivedData release];}

- (void)connectionDidFinishLoading:(NSURLConnection*)connection {
[connectionDelegate performSelector:succeededAction withObject:receivedData];
[receivedData release];}

Answer 1

The static analyser will call this a leak because you are not guaranteeing that either of the methods featuring a release will actually be called.

If you set receivedData as a retained property, and do

self.receivedData = [NSMutableData data];

Then in your dealloc (and also your didFail and didFinish, instead of the release):

self.receivedData = nil;

You will be OK.

As jbat100 points out, you are also leaking url and urlRequest if the !connectionResponse, unless you have omitted this code from the question

Answer 2

You need to make really sure that these two delegate methods are the only possible way the request could finish. I can see a leak here

if (!connectionResponse)
{
    // handle error
    return NO;
}

you do not do the release operations

[url release];
[urlRequest release];

Which you do when the connectionResponse is non-nil. On another note I strongly suggest the ASIHTTP Obj C library for doing this type of stuff.

Answer 3

如果你想删除这个泄漏，请在.h文件中使用NSURLConnection并在connectionDidFinishLoading方法中释放.reason是你在那里分配了NSURLConnection对象但是你不能在那里释放如果释放app杀死那里。这就是为什么你必须创建NSURLConnection对象在.h

Answer 4

Why do you think you are leaking? ( NSMutableData ) If it is because of Xcode's Analyze option; well, it lies, as it can't handle even such obvious complex situations.

However, as Narayana pointed out, you are also leaking the connection, which you should release in both the finish and fail delegate methods.