eprosima::fastdds::dds::DataReaderListener::on_data_available() with const qualifier

[manuelValch]

Hello,

trying to call on_data_available() method directly from my application (instead of calling it from fastdds thread and context).

Though this method does not have a const qualifier and thus can not being called on a Listener obtained via dataReader.get_listener() (which return const).
I can still bypass the issue (with some dirty tricks ctype casts).

Though I wonder if this should be translated as an issue or if there is a cleaner way to call DataReaderListener callbacks ?

[EduPonz]

Hi @manuelValch,

I'm wondering what's your use case; on_data_available() is meant to be called from the library, so I'd like to understand why'd you like to call it in your application code.

[manuelValch]

Hello @EduPonz thank for the answer now it is more clear to me.

Though why does the DataReaderListener callbacks are not const qualified ?

That would allow me to call them on the listener obtained from get_listener().

[EduPonz]

Well, if the DataReaderListener methods were const qualified, it'd mean that the implementation could not do any operation with the DataReader in them. That'd mean that an application could not call take() not take_next_sample() within the on_data_available() as those modify the reader's state.

I still fail to understand why you want to call those methods in the application code, but it seems to me that there should be another way around it.

[manuelValch]

The main reason of why am I calling those callback from application code is because I need those callbacks to be called in the applicative context not fastdds context.

Sorry If I am not being clear I would like to keep the possibility of modification on the dataReader though
i wonder why those callback can not be called on a const subscriber ie
void on_data_available(fdds::DataReader* pReader) const

Because subscriber is not supposed to be modifed by the application in those callbacks is it ?

[EduPonz]

Exactly, if the method is qualified as const then you cannot call any non-const qualified method from it

[manuelValch]

ok thanks.