I'm not trying to insert the c++ class. This code uses the template insert function Query::insert() which uses SQLQuery::insert(). This function uses the class functions table(), field_list() and value_list() from the class supplied as the template class (CLdata). See query1.hh and sql_query1.hh which define these template classes.

<...from sql_query1.hh...> template <class T> SQLQuery& insert(const T &v) { reset(); *this << "INSERT INTO " << v.table() << " (" << v.field_list() << ") VALUES (" << v.value_list() << ")"; return *this; } //: my example is not complete, in that it does not show the value_list implementation, but this usage of insert() simply performs the db INSERT as show above, getting table, fields and values from the classes functions.

this template function is instantiated as: template <class CLdata> Query& Query::insert(const CLdata &v)

the compiler error messsage are: /usr/local/mysql++-1.7.15/sqlplusint/sql_query1.hh: In member function ` SQLQuery& SQLQuery::insert(const T&) [with T = CLdata]': /usr/local/mysql++-1.7.15/sqlplusint/query1.hh:83: instantiated from `MysqlQuery& MysqlQuery::insert(const CLdata&) [with T = CLdata]' cudb.cc:21: instantiated from here /usr/local/mysql++-1.7.15/sqlplusint/sql_query1.hh:178: error: passing `const CLdata' as `this' argument of `std::string& CLdata::value_list()' discards qualifiers /usr/local/mysql++-1.7.15/sqlplusint/sql_query1.hh:178: error: passing `const CLdata' as `this' argument of `std::string& CLdata::field_list()' discards qualifiers /usr/local/mysql++-1.7.15/sqlplusint/sql_query1.hh:178: error: passing `const CLdata' as `this' argument of `SQLString& CLdata::table()' discards qualifiers make[3]: *** [cudb.o] Error 1

Why does is it complaining about 'discards qualifiers'?