extract a boolean from a json value
extract a string type from a json value
extract a numeric type from a json value
extract an enumerated type from a json value
extract an array from a JSONValue
extract an associative array from a JSONValue
extract a value from a json object by its key
extract a value from a json object by its key, return defaultVal if key not found
extract a user-defined class or struct from a JSONValue
json member used to map a json object to a D type
extract!T converts a JSONValue to an instance of T