aliases.md

json_type_alias

It is sometimes desirable to map a class to be parsed like that of another type of mapping or another class. This, can allow parsing the json data as a number and constructing a class.

For instance, we want to store a GNU MP Rational type mpq_class::mpq_class as a string and use it's constructor to parse the data.

namespace daw::json {
  template<>
  struct json_data_contract<mpq_class::mpq_class> {
    using type = json_type_alias<std::string>;
    
    static inline auto to_json_data( mpq_class::mpq_class const & v ) {
        return std::tuple{ return v.get_str( ); }
    }
  };
}

The data for this mapping could look like "12345/56789"

The file cookbook_aliases1_test.cpp shows an example share a type MyClass has a single member of type std::string that is serialized and deserialized as a string.