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GdaDataHandler is implemented by GdaHandlerBin, GdaHandlerBoolean, GdaHandlerNumerical, GdaHandlerString, GdaHandlerTime and GdaHandlerType.
Because data types vary a lot from a DBMS to another, the GdaDataHandler interface helps managing data in its various representations, and converting from one to another:
as a GValue which is a generic value container for the C language
as a human readable string (in the user defined locale)
as an SQL string (a string which can be used in SQL statements)
For each data type, a corresponding GdaDataHandler object can be requested using the
gda_data_handler_get_default() function. However, when working
with a specific database provider, it's better to use a GdaDataHandler which may be specific to the database provider which will correctly handle each database specifics using
gda_server_provider_get_data_handler_g_type() or
gda_server_provider_get_data_handler_dbms().
gchar * gda_data_handler_get_sql_from_value (GdaDataHandler *dh,const GValue *value);
Creates a new string which is an SQL representation of the given value, the returned string
can be used directly in an SQL statement. For example if value
is a G_TYPE_STRING, then
the returned string will be correctly quoted. Note however that it is a better practice
to use variables in statements instead of value literals, see
the GdaSqlParser for more information.
If the value is NULL or is of type GDA_TYPE_NULL,
or is a G_TYPE_STRING and g_value_get_string() returns NULL, the returned string is "NULL".
dh |
an object which implements the GdaDataHandler interface |
|
value |
the value to be converted to a string, or |
[allow-none] |
gchar * gda_data_handler_get_str_from_value (GdaDataHandler *dh,const GValue *value);
Creates a new string which is a "user friendly" representation of the given value (in the user's locale, specially for the dates). If the value is NULL or is of type GDA_TYPE_NULL, the returned string is a copy of "" (empty string).
Note: the returned value will be in the current locale representation.
dh |
an object which implements the GdaDataHandler interface |
|
value |
the value to be converted to a string, or |
[allow-none] |
GValue * gda_data_handler_get_value_from_sql (GdaDataHandler *dh,const gchar *sql,GType type);
Creates a new GValue which represents the SQL value given as argument. This is
the opposite of the function gda_data_handler_get_sql_from_value(). The type argument
is used to determine the real data type requested for the returned value.
If the sql
string is NULL, then the returned GValue is of type GDA_TYPE_NULL;
if the sql
string does not correspond to a valid SQL string for the requested type, then
the NULL is returned.
dh |
an object which implements the GdaDataHandler interface |
|
sql |
an SQL string, or |
[allow-none][transfer none] |
type |
a GType |
GValue * gda_data_handler_get_value_from_str (GdaDataHandler *dh,const gchar *str,GType type);
Creates a new GValue which represents the str
value given as argument. This is
the opposite of the function gda_data_handler_get_str_from_value(). The type argument
is used to determine the real data type requested for the returned value.
If the str
string is NULL, then the returned GValue is of type GDA_TYPE_NULL;
if the str
string does not correspond to a valid string for the requested type, then
NULL is returned.
Note: the str
string must be in the current locale representation
dh |
an object which implements the GdaDataHandler interface |
|
str |
a string or |
[allow-none][transfer none] |
type |
a GType |
GValue * gda_data_handler_get_sane_init_value (GdaDataHandler *dh,GType type);
Creates a new GValue which holds a sane initial value to be used if no value is specifically provided. For example for a simple string, this would return a new value containing the "" string.
gboolean gda_data_handler_accepts_g_type (GdaDataHandler *dh,GType type);
Checks wether the GdaDataHandler is able to handle the gda type given as argument.
const gchar *
gda_data_handler_get_descr (GdaDataHandler *dh);
Get a short description of the GdaDataHandler
GdaDataHandler *
gda_data_handler_get_default (GType for_type);
Obtain a pointer to a GdaDataHandler which can manage GValue values of type for_type
. The returned
data handler will be adapted to use the current locale information (for example dates will be formatted
taking into account the locale).
The returned pointer is NULL if there is no default data handler available for the for_type
data type
Since: 4.2.3