如何使用块取消 ASIFormDataRequest?
__block ASIFormDataRequest *req = [ASIFormDataRequest requestWithURL:url];
[req appendPostData:[str dataUsingEncoding:NSUTF8StringEncoding]];
[req setDelegate:self];
[req setCompletionBlock:^{
[self parseResult:req];
}];
[req setFailedBlock:^{
[self requestWentWrong:req];
}];
[req setTag:tag];
[req startAsynchronous];
有没有办法在按钮操作中取消这个请求?