communication avec http server via CFHTTPMESSAGE

Bonsoir,
J'ai essayé d'implèmenter un code permettant la communucation entre l'iPhone et un serveur web.
d'après ma petite recherche, j'ai trouvé la classe CFHTTPMESSAGE qui devrait répondre à mon besoin.
j'ai implémenté de code

Code:

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CFStringRef bodyData = CFSTR(""); // Usually used for POST data 
	CFStringRef headerFieldName = CFSTR("X-My-Favorite-Field"); 
	CFStringRef headerFieldValue = CFSTR("Dreams"); 
	CFStringRef url = CFSTR("http://www.apple.com"); 
	CFURLRef myURL = CFURLCreateWithString(kCFAllocatorDefault, url, NULL); 
	CFStringRef requestMethod = CFSTR("GET"); 
	CFHTTPMessageRef myRequest = 
    CFHTTPMessageCreateRequest(kCFAllocatorDefault, requestMethod, myURL, 
                               kCFHTTPVersion1_1); 
	CFHTTPMessageSetBody(myRequest, bodyData); 
	CFHTTPMessageSetHeaderFieldValue(myRequest, headerFieldName, headerFieldValue); 
	CFDataRef mySerializedRequest = CFHTTPMessageCopySerializedMessage(myRequest);

mais j'ai reçu ce message d'erreur.

Code:

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Undefined symbols:
  "_CFHTTPMessageCreateRequest", referenced from:
      -[clienthttpv2ViewController myAction:] in clienthttpv2ViewController.o
  "_CFHTTPMessageCopySerializedMessage", referenced from:
      -[clienthttpv2ViewController myAction:] in clienthttpv2ViewController.o
  "_kCFHTTPVersion1_1", referenced from:
      _kCFHTTPVersion1_1$non_lazy_ptr in clienthttpv2ViewController.o
  "_CFHTTPMessageSetHeaderFieldValue", referenced from:
      -[clienthttpv2ViewController myAction:] in clienthttpv2ViewController.o
  "_CFHTTPMessageSetBody", referenced from:
      -[clienthttpv2ViewController myAction:] in clienthttpv2ViewController.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
		  "_CFHTTPMessageCreateRequest", referenced from:
		      -[clienthttpv2ViewController myAction:] in clienthttpv2ViewController.o
		  "_CFHTTPMessageCopySerializedMessage", referenced from:
		      -[clienthttpv2ViewController myAction:] in clienthttpv2ViewController.o
		  "_kCFHTTPVersion1_1", referenced from:
		      _kCFHTTPVersion1_1$non_lazy_ptr in clienthttpv2ViewController.o
		  "_CFHTTPMessageSetHeaderFieldValue", referenced from:
		      -[clienthttpv2ViewController myAction:] in clienthttpv2ViewController.o
		  "_CFHTTPMessageSetBody", referenced from:
		      -[clienthttpv2ViewController myAction:] in clienthttpv2ViewController.o
		ld: symbol(s) not found
		collect2: ld returned 1 exit status

c'est quoi clienthttpv2ViewController.o.