[ndnSIM] How to Distinguish ContentTypes and downcast to them

[Junxiao Shi]

Hi Sabet

When a Data instance is created during packet decoding, the instance is of
Data type, not a subclass of Data. Thus, you cannot downcast it with
static_cast.

If it's determined that the Data is a Link, you may construct a new Link
instance and decode from the wire encoding:

ndn::Link link(data.wireEncode());


Similarly, you can:

ndn::security::v1::Certificate cert(data);

Certificate has a constructor from Data, which allows you to omit
wireEncode().

ContentType=NACK refers to producer generated Nack, which has no particular
structure. A producer generated Nack is just a regular Data.
This is completely unrelated to ndn::lp::Nack.

Yours, Junxiao

On Sun, Oct 9, 2016 at 7:36 AM, Muhammad Hosain Abdollahi Sabet <
mhasabet at gmail.com> wrote:

> ​Hello everyone,
>
> My application recieves a Data packet. How can I downcast it to its Type?
> I mean, for example downcast a data packet to Key or Link or Nack based on
> getContentType of the packet. I know it is more of a c++ question, but
> again I haven't been able to do it yet in ndnSIM.
>
> Thanks,
> Sabet
>
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