Cannot convert SampleInfo timestamps to nanoseconds [19737]

[ryanheidema]

I am having an issue using the source_timestamp and reception_timestamp on a SampleInfo instance retrieved via fastdds.DataReader.take(). Specifically, I want to call to_ns() on the source_timestamp and reception_timestamp and am getting the following error. I have outlined my findings below and would appreciate any help!

terminate called after throwing an instance of 'Swig::DirectorMethodException'
  what():  SWIG director method error. In method 'on_data_available': AttributeError: 'SwigPyObject' object has no attribute 'to_ns'

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I have created the following function, get_data(), which is being used in the callback function to a SubscriberListener class I've created, which overrides the on_data_available( ) method of the fastdds.DataReader.

def get_data(data: fastdds.LoanableCollection, reader: fastdds.DataReader):
    infos: fastdds.SampleInfoSeq = fastdds.SampleInfoSeq()
    ret: fastdds.ReturnCode_t = reader.take(data, infos)
    if ret == fastdds.ReturnCode_t.RETCODE_OK:
        return (data, infos)
    else:
        return None

def callback(reader: fastdds.DataReader):
    data_seq = GeneratedClassSeq()
    data = get_data(data_seq, reader)
    reception_ns = data[1][0].reception_timestamp.to_ns() # line that throws error

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Now, I've checked the generated python bindings in fastdds.py, and do not understand what the issue is. The SampleInfoSeq class defines that I'm using defines __getItem__(), which I am using to get a SampleInfo instance. The SampleInfo class has properties reception_timestamp and source_timestamp, as defined below, which I am accessing via .reception_timestamp. I'm expecting the resultant object from that call to be of type Time_t, which according to fastdds.py has the to_ns() function, but I cannot properly call it.

From fastdds.py:

class SampleInfo(object):
    thisown = property(lambda x: x.this.own(), lambda x, v: x.this.own(v), doc="The membership flag")
    __repr__ = _swig_repr
    ...
    source_timestamp = property(_fastdds_python.SampleInfo_source_timestamp_get, _fastdds_python.SampleInfo_source_timestamp_set)
    reception_timestamp = property(_fastdds_python.SampleInfo_reception_timestamp_get, _fastdds_python.SampleInfo_reception_timestamp_set)
    ...

class Time_t(object):
    thisown = property(lambda x: x.this.own(), lambda x, v: x.this.own(v), doc="The membership flag")
    __repr__ = _swig_repr
    INFINITE_SECONDS = _fastdds_python.Time_t_INFINITE_SECONDS
    INFINITE_NANOSECONDS = _fastdds_python.Time_t_INFINITE_NANOSECONDS
    seconds = property(_fastdds_python.Time_t_seconds_get, _fastdds_python.Time_t_seconds_set)
    nanosec = property(_fastdds_python.Time_t_nanosec_get, _fastdds_python.Time_t_nanosec_set)

    def __init__(self, *args):
        _fastdds_python.Time_t_swiginit(self, _fastdds_python.new_Time_t(*args))

    def fraction(self, *args):
        return _fastdds_python.Time_t_fraction(self, *args)

    def to_ns(self):
        return _fastdds_python.Time_t_to_ns(self)
    ...

---

Documentation Referenced:

• 18.1.4.7 SampleInfo: https://fast-dds.docs.eprosima.com/en/latest/fastdds/python_api_reference/dds_pim/subscriber/sampleinfo.html

[richiware]

#68 should fix your problem.