MySQL NDB Cluster API Developer Guide
Converter classes convert between JavaScript types and MySQL types. If the user supplies a JavaScript converter, it used to read and write to the database.
Converters have several purposes, including the following:
The ndb back end also uses converters to support
SET
and
ENUM
columns. (The mysql back end
does not use these.)
A Converter
class has the interface defined
here:
function Converter() {}: Converter.prototype = { "toDB" : function(obj
) { }, "fromDB" : function(val
) { } };
The Converter
must
implement the following two functions:
toDB(
:
Convert an application object obj
)obj
into a form that can be stored in the database.
fromDB(
:
Convert a value val
)val
read from the
database into application object format.
Each function returns the result of the conversion.
Converter invocations are chained in the following ways:
When writing to the database, first the registered
FieldConverter
, if any, is invoked.
Later, any registered TypeConverter
is
invoked.
When reading from the database, first the registered
TypeConverter
, if any, is invoked. Later,
any registered FieldConverter
is invoked.