非同步網路探究

NSURLConnection:

+ (void)sendAsynchronousRequest:(NSURLRequest *)request

                          queue:(NSOperationQueue*) queue

              completionHandler:(void (^)(NSURLResponse*, NSData*, NSError*)) handler

->

When the request has completed or failed, the block will be executed from the context of the

specified NSOperationQueue

ex:

NSOperationQueue *queue = [[NSOperationQueue alloc] init];

[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue 

                           completionHandler:^(NSURLResponse *response,    

                                    NSData *data, NSError *error) 

 {

         NSLog(@"thread %p %p", [NSThread currentThread], [NSThread mainThread]);

}];

->   currentThread != mainThread

NSOperationQueue *queue = [NSOperationQueue currentQueue];

[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue 

                           completionHandler:^(NSURLResponse *response,    

                                    NSData *data, NSError *error) 

 {

         NSLog(@"thread %p %p", [NSThread currentThread], [NSThread mainThread]);

}];

->   currentThread == mainThread

block和物件生命的關係:


假設呼叫以下method


 [NSURLConnection sendAsynchronousRequest:req queue:[NSOperationQueue currentQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {

}];
如果block裡帶有某個物件，則此物件將維持生命直到block執行完。