Accessing default value in schema

[Mark Petronic]

I am getting back into C++ but don't have much experience with templates so
I am a reaching out for a hint here. I am trying to iterate over all the
NodePrt nodes starting with the root node using avro::NodePtr& root =
schema.root(); But I just cannot figure out how to code up the method call
to get the default value from a primitive whose schema defines one. For
example, a simple schema like this:

{
    "name": "simple_schema",
    "type": "record",
    "fields": [
        {
            "name": "int_stat",
            "type": "long",
            "default": 999
        }
    ]
}

I want to get my hands on that 999 value. Here is a snippet of a method
that gets a NodePtr to an Avro record, retrieves the defaultValueAt(i) just
fine, but how do I code up the call to retrieve the value() 999?

   1. What should the return value look like given the default could be
   various types depending on the schema?
   2. What should this call look like?  default_value.value();

Thanks for any insight and guidance!!!

void Encoder::encode_record(
        const avro::NodePtr& n,
        const csv_data_map& csv_data,
        avro::EncoderPtr encoder) const
{
    size_t c = n->leaves();
    cout << "Processing Avro record, name = " << n->name() << endl;
    for (size_t i = 0; i < c; ++i) {
        avro::GenericDatum default_value = n->defaultValueAt(i);
        // THIS IS THE PROBLEM PART I CANNOT FIGURE OUT
        default_value.value();
        encode_type(n->leafAt(i), n->nameAt(i), csv_data, encoder,
default_value);
    }
}

Building file: ../src/encoder.cpp
Invoking: GCC C++ Compiler
g++ -std=c++0x -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP
-MF"src/encoder.d" -MT"src/encoder.o" -o "src/encoder.o"
"../src/encoder.cpp"
../src/encoder.cpp: In member function ‘void Encoder::encode_record(const
NodePtr&, const csv_data_map&, avro::EncoderPtr) const’:
../src/encoder.cpp:257:29: error: no matching function for call to
‘avro::GenericDatum::value()’
         default_value.value();
                             ^
../src/encoder.cpp:257:29: note: candidates are:
In file included from ../src/encoder.cpp:7:0:
/usr/local/include/avro/GenericDatum.hh:98:35: note: template<class T>
const T& avro::GenericDatum::value() const
     template<typename T> const T& value() const;
                                   ^
/usr/local/include/avro/GenericDatum.hh:98:35: note:   template argument
deduction/substitution failed:
../src/encoder.cpp:257:29: note:   couldn't deduce template parameter ‘T’
         default_value.value();
                             ^
In file included from ../src/encoder.cpp:7:0:
/usr/local/include/avro/GenericDatum.hh:109:29: note: template<class T> T&
avro::GenericDatum::value()
     template<typename T> T& value();
                             ^
/usr/local/include/avro/GenericDatum.hh:109:29: note:   template argument
deduction/substitution failed:
../src/encoder.cpp:257:29: note:   couldn't deduce template parameter ‘T’
         default_value.value();
                             ^
make: *** [src/encoder.o] Error 1