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GNOME Data Access 3.0 manual | ![]() |
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GdaDataHandler; gchar* gda_data_handler_get_sql_from_value (GdaDataHandler *dh, const GValue *value); gchar* gda_data_handler_get_str_from_value (GdaDataHandler *dh, const GValue *value); GValue* gda_data_handler_get_value_from_sql (GdaDataHandler *dh, const gchar *sql, GType type); GValue* gda_data_handler_get_value_from_str (GdaDataHandler *dh, const gchar *str, GType type); GValue* gda_data_handler_get_sane_init_value (GdaDataHandler *dh, GType type); guint gda_data_handler_get_nb_g_types (GdaDataHandler *dh); gboolean gda_data_handler_accepts_g_type (GdaDataHandler *dh, GType type); GType gda_data_handler_get_g_type_index (GdaDataHandler *dh, guint index); const gchar* gda_data_handler_get_descr (GdaDataHandler *dh);
GdaDataHandler is implemented by GdaHandlerBoolean, GdaHandlerType, GdaHandlerBin, GdaHandlerNumerical, GdaHandlerTime and GdaHandlerString.
Because data types vary a lot from a DBMS to another, the GdaDataHandler interface helps designing modules which can handle very specific pieces of data through plugins. Each object which imlements the GdaDataHandler interface is expected to handle a subset of the possible libgda defined data types.
The GdaDataHandler object can convert a GValue to and from both SQL and 'STR'. The SQL representation of a value is the actual string which would be used in an SQL statement (for example a string's SQL representation is surrounded by quotes such as 'that\'s a string'). The 'STR' representation is a user friendly representation of a value (and the previous example would simply be: that's a string).
Only one object which implements this interface is needed for any given data type, and it mainly contains some methods to manage values (as GValue structures). The GnomeDbDataEntry interface is complementary to this one since it it implemented by widgets where the user can enter or modify some data.
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. If the value is NULL or is of type GDA_TYPE_NULL, the returned string is NULL.
dh : |
an object which implements the GdaDataHandler interface |
value : |
the value to be converted to a string |
Returns : | the new string. |
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 users'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).
dh : |
an object which implements the GdaDataHandler interface |
value : |
the value to be converted to a string |
Returns : | the new string. |
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 NULL is returned.
dh : |
an object which implements the GdaDataHandler interface |
sql : |
|
type : |
|
Returns : | the new GValue or NULL on error |
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 STR string for the requested type, then NULL is returned.
dh : |
an object which implements the GdaDataHandler interface |
str : |
|
type : |
|
Returns : | the new GValue or NULL on error |
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.
dh : |
an object which implements the GdaDataHandler interface |
type : |
|
Returns : | the new GValue, or NULL if no such value can be created.
|
guint gda_data_handler_get_nb_g_types (GdaDataHandler *dh);
Get the number of GType types the GdaDataHandler can handle correctly
dh : |
an object which implements the GdaDataHandler interface |
Returns : | the number. |
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.
dh : |
an object which implements the GdaDataHandler interface |
type : |
|
Returns : | TRUE if the gda type can be handled |
GType gda_data_handler_get_g_type_index (GdaDataHandler *dh, guint index);
Get the GType handled by the GdaDataHandler, at the given position (starting at zero).
dh : |
an object which implements the GdaDataHandler interface |
index : |
|
Returns : | the GType |
const gchar* gda_data_handler_get_descr (GdaDataHandler *dh);
Get a short description of the GdaDataHandler
dh : |
an object which implements the GdaDataHandler interface |
Returns : | the description |