ios - I get error when use AFNetworking in xcode for download file -

i create 1 application has 1 page , in page exist 1 button downloaded file when click on.

i can download file afnetworking in has error ....

this code :

- (ibaction)downloads:(id)sender {     nslog(@"start downloads");     nsurlrequest *request = [nsurlrequest requestwithurl:    [nsurl urlwithstring:    @"http://.../500x333xgalaxy-core-product-image-1tn.jpg,                            q1367836642.pagespeed.ic.eafbyu8jun.jpg"]];     afurlconnectionoperation *operation = [[afhttprequestoperation alloc]                                                              initwithrequest:request];     nsarray *paths = nssearchpathfordirectoriesindomains(nsdocumentdirectory,                                                                     nsuserdomainmask, yes);     nsstring *path = [[paths objectatindex:0] stringbyappendingpathcomponent                                                                         :@"filename.jpg"];      operation.outputstream = [nsoutputstream outputstreamtofileatpath:path append:no];      [operation setcompletionblockwithsuccess:^(afhttprequestoperation *operation,      id responseobject) {         nslog(@"successfully downloaded file %@", path);     } failure:^(afhttprequestoperation *operation, nserror *error) {         nslog(@"error: %@", error);     }];  } 

this error :

no visible @interface 'afurlconnectionopretion' declares selector                                                          'setcompletionblockwithsuccess' 

use following line start operation :

[operation start];