后台线程上的 NSURLConnection 委托方法

EDIT2 - 重写问题

我想在后台进行一些网络服务通信。我在用Sudzc http://sudzc.com/作为 HTTPRequests 的处理程序，它的工作原理如下：

SudzcWS *service = [[SudzcWS alloc] init];
[service sendOrders:self withXML:@"my xml here" action:@selector(handleOrderSending:)];
[service release];

它将一些 XML 发送到 Web 服务，并在指定的选择器中处理响应（在本例中为布尔值）：

- (void)handleOrderSending:(id)value
{ 
//some controls  
    if ([value boolValue] == YES)
    {
        //my stuff
    }
}

当我尝试在我的电脑上使用 Grand Central Dispatch 时sendOrders:withXML:action:方法，我注意到选择器没有被调用。我相信原因是NSURLConnection 委托消息发送到创建连接的线程但线程的生存时间并不长，它会在方法完成时结束，并杀死发送给委托的所有消息。

Regards

EDIT1 [request send] method:

- (void) send {
//dispatch_async(backgroundQueue, ^(void){
    // If we don't have a handler, create a default one
    if(handler == nil) {
        handler = [[SoapHandler alloc] init];
    }

    // Make sure the network is available
    if([SoapReachability connectedToNetwork] == NO) {
        NSError* error = [NSError errorWithDomain:@"SudzC" code:400 userInfo:[NSDictionary dictionaryWithObject:@"The network is not available" forKey:NSLocalizedDescriptionKey]];
        [self handleError: error];
    }

    // Make sure we can reach the host
    if([SoapReachability hostAvailable:url.host] == NO) {
        NSError* error = [NSError errorWithDomain:@"SudzC" code:410 userInfo:[NSDictionary dictionaryWithObject:@"The host is not available" forKey:NSLocalizedDescriptionKey]];
        [self handleError: error];
    }

    // Output the URL if logging is enabled
    if(logging) {
        NSLog(@"Loading: %@", url.absoluteString);
    }

    // Create the request
    NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL: url];
    if(soapAction != nil) {
        [request addValue: soapAction forHTTPHeaderField: @"SOAPAction"];
    }
    if(postData != nil) {
        [request setHTTPMethod: @"POST"];
        [request addValue: @"text/xml; charset=utf-8" forHTTPHeaderField: @"Content-Type"];
        [request setHTTPBody: [postData dataUsingEncoding: NSUTF8StringEncoding]];

        if(self.logging) {
            NSLog(@"%@", postData);
        }
    }


    //dispatch_async(dispatch_get_main_queue(), ^(void){
        // Create the connection
        conn = [[NSURLConnection alloc] initWithRequest: request delegate: self];
        if(conn) {
                                        NSLog(@" POST DATA %@", receivedData);
            receivedData = [[NSMutableData data] retain];
                        NSLog(@" POST DATA %@", receivedData);
        } else {
            // We will want to call the onerror method selector here...
            if(self.handler != nil) {
                NSError* error = [NSError errorWithDomain:@"SoapRequest" code:404 userInfo: [NSDictionary dictionaryWithObjectsAndKeys: @"Could not create connection", NSLocalizedDescriptionKey,nil]];
                [self handleError: error];
            }
        }
    //});


    //finished = NO;

    //    while(!finished) {
    //        
    //        [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
    //        
    //    }

//});
}

被注释掉的部分是我尝试过的各种事情。最后一部分有效，但我不确定这是否是一个好方法。在里面NURLConnection类的委托方法，发生的情况如下：

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
NSError* error;
if(self.logging == YES) {
    NSString* response = [[NSString alloc] initWithData: self.receivedData     encoding: NSUTF8StringEncoding];
    NSLog(@"%@", response);
    [response release];
}

CXMLDocument* doc = [[CXMLDocument alloc] initWithData: self.receivedData options: 0 error: &error];
if(doc == nil) {
    [self handleError:error];
    return;
}

id output = nil;
SoapFault* fault = [SoapFault faultWithXMLDocument: doc];

if([fault hasFault]) {
    if(self.action == nil) {
        [self handleFault: fault];
    } else {
        if(self.handler != nil && [self.handler respondsToSelector: self.action]) {

                [self.handler performSelector: self.action withObject: fault];


        } else {
            NSLog(@"SOAP Fault: %@", fault);
        }
    }
} else {
    CXMLNode* element = [[Soap getNode: [doc rootElement] withName: @"Body"] childAtIndex:0];
    if(deserializeTo == nil) {
        output = [Soap deserialize:element];
    } else {
        if([deserializeTo respondsToSelector: @selector(initWithNode:)]) {
            element = [element childAtIndex:0];
            output = [deserializeTo initWithNode: element];
        } else {
            NSString* value = [[[element childAtIndex:0] childAtIndex:0] stringValue];
            output = [Soap convert: value toType: deserializeTo];
        }
    }

    if(self.action == nil) { self.action = @selector(onload:); }
    if(self.handler != nil && [self.handler respondsToSelector: self.action]) {


            [self.handler performSelector: self.action withObject: output];


    } else if(self.defaultHandler != nil && [self.defaultHandler respondsToSelector:@selector(onload:)]) {
        [self.defaultHandler onload:output];
    }
}

[self.handler release];
[doc release];
[conn release];
conn = nil;
[self.receivedData release];
}

委托无法发送消息，因为它所在的线程在以下情况下死亡-(void)send完成。

方法定义为sendOrders表明它已经被设计为以异步方式执行请求。您应该查看一下实施情况sendOrders: withXML: action:看看情况是否如此。

如果没有看到使用 GCD 的实现或 SudzcWS 的代码，很难说出了什么问题。尽管有前面的警告，以下内容可能有用。

看来你可能要释放SudzcWS *service在它完成之前。

下列：

SudzcWS *service = [[SudzcWS alloc] init];
dispatch_async(aQueue, ^{
    [sevice sendOrders:self withXML:xml action:@selector(handleOrderSending:)];
}
[service release];

除非 SudzcWS 保住自己，否则可能会失败。您异步分派块，将其放入队列中，然后继续执行该方法。service在块执行之前或同时被释放并被释放service正在等待网络服务器的响应。

除非另有指定，否则调用选择器将在调用它的同一线程上执行该选择器。做类似的事情：

SudzcWS *service = [[SudzcWS alloc] init];
dispatch_async(aQueue, ^{
    [sevice sendOrders:self withXML:xml action:@selector(handleOrderSending:)];
}


- (void)handleOrderSending:(id)value
{ 
    //some controls  
    //your stuff
    [service release];
}

应确保双方sendOrders:方法和handleOrderSending:在队列上执行aQueue然后service在执行选择器之前不会被释放。

这将要求您保留一个指向service以便handleOrderSending:可以释放它。您可能还想考虑简单地挂在单个 SudzcWS 实例上，而不是每次要使用它时创建和释放一个实例，这应该使您的内存管理更加容易，并有助于保持对象图的紧凑。