NSURL *url = [NSURL URLWithString:@"url"];
//需要提交的到服務器的json串
NSString *json2 = @"{\"conference_id\":22, \"agenda_id\":\"4\", \"twocode\":{\"id\":\"45\"}}";
//轉成data形式 因爲postBody返回是NSMutabledata所以需要強轉
NSMutableData *data = (NSMutableData*)[json2 dataUsingEncoding:NSUTF8StringEncoding];
ASIFormDataRequest *aRequest = [[ASIFormDataRequest alloc] initWithURL:url];
[aRequest setDelegate:self];//代理
[aRequest setRequestMethod:@"POST"];
[aRequest setPostBody:data];
[aRequest startAsynchronous];