Record: A heterogeneous data structure for C++

Record provides a linear, direct accessible data structure with heterogeneous entries.

A record type will be defined with the macro BRAINTWISTER_RECORD.

BRAINTWISTER_RECORD( record_name, \
    (( field_type, field_name, field_default_value )) \
    ... \
) 

For example a database connection type can be defined by

BRAINTWISTER_RECORD( Database, \
    (( std::string, host, "localhost" )) \
    (( uint16_t, port, 3306 )) \
    (( std::string, database, "sensors" )) \
    (( std::string, user, "ruuvi" )) \
    (( std::string, password, "" )) \
)

The entry default values are mandatory.

Construction

auto database = Database().host("staging").port(9876);

Construction by JSON or XML

It is also possible to construct an object by JSON or XML. The construction is order independent and use the default values if it is not given in JSON/XML.

auto json_string = R"(
    {
        "port": 9876,
        "host": "staging",
    }
)";

DatabaseConnector db(JSON(json_string));

Here, the string literal R is only used to avoid the escape of the quotation marks for a better readability. The XML initialization is similar.

auto xml_string = "
    <port>9876</port>
    <host>staging</host>
";

DatabaseConnector db(XML(xml_string));

Example: Functor state

When using functors it is advantageous to separate the state into a passive data structure (PDS).

struct Settings
{
    std::string host;
    uint16_t port;
    std::string database;
    std::string user;
    std::string password;
}

struct Functor
{
    Functor(Settings const& settings)
     : settings(settings)
    {}

    void operator()() const;

  private:

    Settings settings;
}