如何在使用MKNetworking弹出视图时取消GET请求，我不希望它冻结并在以后恢复

Question

MKNetworkEngine *engine = [[MKNetworkEngine alloc] initWithHostName:@"support.sample.com" customHeaderFields:nil];

MKNetworkOperation *op = [engine operationWithPath:YAHOO_URL(@"abc123@gmail.com", @"123") params:nil httpMethod:@"GET" ssl:YES];
[op freezable];

[op addCompletionHandler:^(MKNetworkOperation *operation)
 {
    NSLog(@"[operation responseData]-->>%@", [operation responseString]);
 }

errorHandler:^(MKNetworkOperation *errorOp, NSError* err)
 {
    NSLog(@"MKNetwork request error : %@", [err localizedDescription]);
 }];

[engine enqueueOperation:op];



#define YAHOO_URL(__C1__, __C2__) [NSString stringWithFormat:@"/sampleLOgin?MUserEmail=%@&SAMRegId=%@", __C1__, __C2__]