## GdaDataModel

GdaDataModel — Basic data model class

## Synopsis

                        GdaDataModel;
    enum                GdaDataModelAccessFlags;
    enum                GdaDataModelHint;
    enum                GdaDataModelIOFormat;
    void                gda_data_model_row_inserted         (GdaDataModel *model,
                                                             gint row);
    void                gda_data_model_row_updated          (GdaDataModel *model,
                                                             gint row);
    void                gda_data_model_row_removed          (GdaDataModel *model,
                                                             gint row);
    void                gda_data_model_freeze               (GdaDataModel *model);
    void                gda_data_model_thaw                 (GdaDataModel *model);
    GdaDataModelAccessFlags gda_data_model_get_access_flags (GdaDataModel *model);
    gint                gda_data_model_get_n_rows           (GdaDataModel *model);
    gint                gda_data_model_get_n_columns        (GdaDataModel *model);
    GdaColumn*          gda_data_model_describe_column      (GdaDataModel *model,
                                                             gint col);
    gint                gda_data_model_get_column_index_by_name
                                                            (GdaDataModel *model,
                                                             const gchar *name);
    const gchar*        gda_data_model_get_column_title     (GdaDataModel *model,
                                                             gint col);
    void                gda_data_model_set_column_title     (GdaDataModel *model,
                                                             gint col,
                                                             const gchar *title);
    GdaValueAttribute   gda_data_model_get_attributes_at    (GdaDataModel *model,
                                                             gint col,
                                                             gint row);
    const GValue*       gda_data_model_get_value_at         (GdaDataModel *model,
                                                             gint col,
                                                             gint row);
    const GValue*       gda_data_model_get_value_at_col_name
                                                            (GdaDataModel *model,
                                                             const gchar *column_name,
                                                             gint row);
    gboolean            gda_data_model_set_value_at         (GdaDataModel *model,
                                                             gint col,
                                                             gint row,
                                                             const GValue *value,
                                                             GError **error);
    gboolean            gda_data_model_set_values           (GdaDataModel *model,
                                                             gint row,
                                                             GList *values,
                                                             GError **error);
    GdaDataModelIter*   gda_data_model_create_iter          (GdaDataModel *model);
    gint                gda_data_model_append_values        (GdaDataModel *model,
                                                             const GList *values,
                                                             GError **error);
    gint                gda_data_model_append_row           (GdaDataModel *model,
                                                             GError **error);
    gboolean            gda_data_model_remove_row           (GdaDataModel *model,
                                                             gint row,
                                                             GError **error);
    gint                gda_data_model_get_row_from_values  (GdaDataModel *model,
                                                             GSList *values,
                                                             gint *cols_index);
    void                gda_data_model_send_hint            (GdaDataModel *model,
                                                             GdaDataModelHint hint,
                                                             const GValue *hint_value);
    gchar*              gda_data_model_export_to_string     (GdaDataModel *model,
                                                             GdaDataModelIOFormat format,
                                                             const gint *cols,
                                                             gint nb_cols,
                                                             const gint *rows,
                                                             gint nb_rows,
                                                             GdaParameterList *options);
    gboolean            gda_data_model_export_to_file       (GdaDataModel *model,
                                                             GdaDataModelIOFormat format,
                                                             const gchar *file,
                                                             const gint *cols,
                                                             gint nb_cols,
                                                             const gint *rows,
                                                             gint nb_rows,
                                                             GdaParameterList *options,
                                                             GError **error);
    gboolean            gda_data_model_add_data_from_xml_node
                                                            (GdaDataModel *model,
                                                             xmlNodePtr node,
                                                             GError **error);
    gboolean            gda_data_model_import_from_model    (GdaDataModel *to,
                                                             GdaDataModel *from,
                                                             gboolean overwrite,
                                                             GHashTable *cols_trans,
                                                             GError **error);
    gboolean            gda_data_model_import_from_string   (GdaDataModel *model,
                                                             const gchar *string,
                                                             GHashTable *cols_trans,
                                                             GdaParameterList *options,
                                                             GError **error);
    gboolean            gda_data_model_import_from_file     (GdaDataModel *model,
                                                             const gchar *file,
                                                             GHashTable *cols_trans,
                                                             GdaParameterList *options,
                                                             GError **error);
    void                gda_data_model_dump                 (GdaDataModel *model,
                                                             FILE *to_stream);
    gchar*              gda_data_model_dump_as_string       (GdaDataModel *model);

## Object Hierarchy

      GInterface
       +----GdaDataModel

## Prerequisites

GdaDataModel requires GdaObject.

## Known Implementations

GdaDataModel is implemented by GdaDataModelFilterSQL, GdaDataProxy, GdaDataModelRow, GdaDataModelHash, GdaDataModelQuery, GdaDataAccessWrapper, GdaDataModelImport and GdaDataModelArray.

## Signals

      "reset"                                          : Run Last
      "row-inserted"                                   : Run Last
      "row-removed"                                    : Run Last
      "row-updated"                                    : Run Last

## Description

A GdaDataMode represents an array of values organized in rows and columns. All the data in the same column have the same type, and all the data in each row have the same semantic meaning. The GdaDataModel is actually an interface implemented by other objects to support various kinds of data storage and operations.

Depending on the real implementation, the contents of data models may be modified by the user using functions provided by the model. The actual operations a data model permits can be known using the `gda_data_model_get_access_flags()` method.

Again, depending on the real implementation, data retreiving can be done either accessing direct random values located by their row and column, or using a GdaDataModelIter cursor, or both. Use the `gda_data_model_get_access_flags()` method to know how the data model can be accessed. Note that a GdaDatamodel which can be accessed in a random way can also be accessed using cursors (and several cusrors may be used at the same time), whereas data model which can only be accessed using cursors can only have one cursor for iterating.

Random access data models are easier to use since picking a value is very simple using the `gda_data_model_get_value_at()`, but consume more memory since all the accessible values must generally be present in memory even if they are not used. Thus if a data model must handle large quantities of data, it is generally wiser to use a data model which can be only accessed using a cursor.

As a side note there are also data models which wrap other data models such as:

- The GdaDataProxy data model which stores temporary modifications and shows only some parts of the wrapped data model

- The GdaDataAccessWrapper data model which offers a memory-efficient random access on top of a wrapped cursor based access data model

## Details

### GdaDataModel

    typedef struct _GdaDataModel GdaDataModel;

### enum GdaDataModelAccessFlags

    typedef enum {
    	GDA_DATA_MODEL_ACCESS_RANDOM = 1 << 0,
    	GDA_DATA_MODEL_ACCESS_CURSOR_FORWARD = 1 << 1,
    	GDA_DATA_MODEL_ACCESS_CURSOR_BACKWARD = 1 << 2,
    	GDA_DATA_MODEL_ACCESS_INSERT  = 1 << 3,
    	GDA_DATA_MODEL_ACCESS_UPDATE  = 1 << 4,
    	GDA_DATA_MODEL_ACCESS_DELETE  = 1 << 5,
    	GDA_DATA_MODEL_ACCESS_WRITE = GDA_DATA_MODEL_ACCESS_INSERT | GDA_DATA_MODEL_ACCESS_UPDATE |
    	GDA_DATA_MODEL_ACCESS_DELETE,
    } GdaDataModelAccessFlags;

### enum GdaDataModelHint

    typedef enum {
    	GDA_DATA_MODEL_HINT_START_BATCH_UPDATE,
    	GDA_DATA_MODEL_HINT_END_BATCH_UPDATE,
    	GDA_DATA_MODEL_HINT_REFRESH,
    } GdaDataModelHint;

### enum GdaDataModelIOFormat

    typedef enum {
    	GDA_DATA_MODEL_IO_DATA_ARRAY_XML,
    	GDA_DATA_MODEL_IO_TEXT_SEPARATED,
    } GdaDataModelIOFormat;

### gda_data_model_row_inserted ()

    void                gda_data_model_row_inserted         (GdaDataModel *model,
                                                             gint row);

Emits the 'row_inserted' and 'changed' signals on `model`.

`model` : | a GdaDataModel object.
`row` : | row number.

### gda_data_model_row_updated ()

    void                gda_data_model_row_updated          (GdaDataModel *model,
                                                             gint row);

Emits the 'row_updated' and 'changed' signals on `model`.

`model` : | a GdaDataModel object.
`row` : | row number.

### gda_data_model_row_removed ()

    void                gda_data_model_row_removed          (GdaDataModel *model,
                                                             gint row);

Emits the 'row_removed' and 'changed' signal on `model`.

`model` : | a GdaDataModel object.
`row` : | row number.

### gda_data_model_freeze ()

    void                gda_data_model_freeze               (GdaDataModel *model);

Disables notifications of changes on the given data model. To re-enable notifications again, you should call the gda_data_model_thaw function.

`model` : | a GdaDataModel object.

### gda_data_model_thaw ()

    void                gda_data_model_thaw                 (GdaDataModel *model);

Re-enables notifications of changes on the given data model.

`model` : | a GdaDataModel object.

### gda_data_model_get_access_flags ()

    GdaDataModelAccessFlags gda_data_model_get_access_flags (GdaDataModel *model);

Get the attributes of `model` such as how to access the data it contains if it's modifiable, etc.

`model` : | a GdaDataModel object.
Returns : | an ORed value of GdaDataModelAccessFlags flags

### gda_data_model_get_n_rows ()

    gint                gda_data_model_get_n_rows           (GdaDataModel *model);

`model` : | a GdaDataModel object.
Returns : | the number of rows in the given data model, or -1 if the number of rows is not known

### gda_data_model_get_n_columns ()

    gint                gda_data_model_get_n_columns        (GdaDataModel *model);

`model` : | a GdaDataModel object.
Returns : | the number of columns in the given data model.

### gda_data_model_describe_column ()

    GdaColumn*          gda_data_model_describe_column      (GdaDataModel *model,
                                                             gint col);

Queries the underlying data model implementation for a description of a given column. That description is returned in the form of a GdaColumn structure, which contains all the information about the given column in the data model.

WARNING: the returned GdaColumn object belongs to the `model` model and and should not be destroyed; any modification will affect the whole data model.

`model` : | a GdaDataModel object.
`col` : | column number.
Returns : | the description of the column.

### gda_data_model_get_column_index_by_name ()

    gint                gda_data_model_get_column_index_by_name
                                                            (GdaDataModel *model,
                                                             const gchar *name);

Get the index of the column named `name` in `model`

`model` : | a GdaDataModel object.
`name` : | a column name
Returns : | the column index, or -1 if no column named `name` was found

### gda_data_model_get_column_title ()

    const gchar*        gda_data_model_get_column_title     (GdaDataModel *model,
                                                             gint col);

`model` : | a GdaDataModel object.
`col` : | column number.
Returns : | the title for the given column in a data model object.

### gda_data_model_set_column_title ()

    void                gda_data_model_set_column_title     (GdaDataModel *model,
                                                             gint col,
                                                             const gchar *title);

Sets the `title` of the given `col` in `model`.

`model` : | a GdaDataModel object.
`col` : | column number
`title` : | title for the given column.

### gda_data_model_get_attributes_at ()

    GdaValueAttribute   gda_data_model_get_attributes_at    (GdaDataModel *model,
                                                             gint col,
                                                             gint row);

Get the attributes of the value stored at (row, col) in `proxy`, which is an ORed value of GdaValueAttribute flags. As a special case, if `row` is -1, then the attributes returned correspond to a "would be" value if a row was added to `model`.

`model` : | a GdaDataModel object
`col` : | a valid column number
`row` : | a valid row number, or -1
Returns : | the attributes as an ORed value of GdaValueAttribute

### gda_data_model_get_value_at ()

    const GValue*       gda_data_model_get_value_at         (GdaDataModel *model,
                                                             gint col,
                                                             gint row);

Retrieves the data stored in the given position (identified by the `col` and `row` parameters) on a data model.

This is the main function for accessing data in a model.

Note that the returned GValue must not be modified directly (unexpected behaviours may occur if you do so). If you want to modify a value stored in a GdaDataModel, use the `gda_data_model_set_value()` method.

`model` : | a GdaDataModel object.
`col` : | a valid column number.
`row` : | a valid row number.
Returns : | a GValue containing the value stored in the given position, or `NULL` on error (out-of-bound position, etc).

### gda_data_model_get_value_at_col_name ()

    const GValue*       gda_data_model_get_value_at_col_name
                                                            (GdaDataModel *model,
                                                             const gchar *column_name,
                                                             gint row);

Retrieves the data stored in the given position (identified by the `col_name` column and `row` parameters) on a data model.

See also `gda_data_model_get_value_at()`.

`model` : | a GdaDataModel object.
`column_name` : | a valid column name.
`row` : | a valid row number.
Returns : | a GValue containing the value stored in the given position, or `NULL` on error (out-of-bound position, etc).

### gda_data_model_set_value_at ()

    gboolean            gda_data_model_set_value_at         (GdaDataModel *model,
                                                             gint col,
                                                             gint row,
                                                             const GValue *value,
                                                             GError **error);

`model` : | a GdaDataModel object.
`col` : | column number.
`row` : | row number.
`value` : | a GValue, or `NULL`
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if the value in the data model has been updated and no error occurred

### gda_data_model_set_values ()

    gboolean            gda_data_model_set_values           (GdaDataModel *model,
                                                             gint row,
                                                             GList *values,
                                                             GError **error);

If any value in `values` is actually `NULL`, then it is considered as a default value.

`model` : | a GdaDataModel object.
`row` : | row number.
`values` : | a list of GValue, one for each n (<nb_cols) columns of `model`
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if the value in the data model has been updated and no error occurred

### gda_data_model_create_iter ()

    GdaDataModelIter*   gda_data_model_create_iter          (GdaDataModel *model);

Creates a new iterator object GdaDataModelIter object which can be used to iterate through rows in `model`.

The row the returned GdaDataModelIter represents is undefined. For models which can be accessed randomly the correspoding row can be set using `gda_data_model_move_iter_at_row()`, and for models which are accessible sequentially only then the first row will be fetched using `gda_data_model_move_iter_next()`.

`model` : | a GdaDataModel object.
Returns : | a new GdaDataModelIter object, or `NULL` if an error occurred

### gda_data_model_append_values ()

    gint                gda_data_model_append_values        (GdaDataModel *model,
                                                             const GList *values,
                                                             GError **error);

Appends a row to the given data model. If any value in `values` is actually `NULL`, then it is considered as a default value.

`model` : | a GdaDataModel object.
`values` : | GList of GValue* representing the row to add. The length must match model's column count. These GValue are value-copied (the user is still responsible for freeing them).
`error` : | a place to store errors, or `NULL`
Returns : | the number of the added row, or -1 if an error occurred

### gda_data_model_append_row ()

    gint                gda_data_model_append_row           (GdaDataModel *model,
                                                             GError **error);

Appends a row to the data model.

`model` : | a GdaDataModel object.
`error` : | a place to store errors, or `NULL`
Returns : | the number of the added row, or -1 if an error occurred

### gda_data_model_remove_row ()

    gboolean            gda_data_model_remove_row           (GdaDataModel *model,
                                                             gint row,
                                                             GError **error);

Removes a row from the data model.

`model` : | a GdaDataModel object.
`row` : | the row number to be removed.
`error` : | a place to store errors, or `NULL`
Returns : | `TRUE` if successful, `FALSE` otherwise.

### gda_data_model_get_row_from_values ()

    gint                gda_data_model_get_row_from_values  (GdaDataModel *model,
                                                             GSList *values,
                                                             gint *cols_index);

Returns the first row where all the values in `values` at the columns identified at `cols_index` match. If the row can't be identified, then returns -1;

NOTE: the `cols_index` array MUST contain a column index for each value in `values`

`model` : | a GdaDataModel object.
`values` : | a list of GValue values
`cols_index` : | an array of gint containing the column number to match each value of `values`
Returns : | the requested row number, of -1 if not found

### gda_data_model_send_hint ()

    void                gda_data_model_send_hint            (GdaDataModel *model,
                                                             GdaDataModelHint hint,
                                                             const GValue *hint_value);

Sends a hint to the data model. The hint may or may not be handled by the data model, depending on its implementation

`model` : | a GdaDataModel
`hint` : | a hint to send to the model
`hint_value` : | an optional value to specify the hint, or `NULL`

### gda_data_model_export_to_string ()

    gchar*              gda_data_model_export_to_string     (GdaDataModel *model,
                                                             GdaDataModelIOFormat format,
                                                             const gint *cols,
                                                             gint nb_cols,
                                                             const gint *rows,
                                                             gint nb_rows,
                                                             GdaParameterList *options);

Exports data contained in `model` to a string; the format is specified using the `format` argument.

Specifically, the parameters in the `options` list can be:

- "SEPARATOR": a string value of which the first character is used as a separator in case of CSV export

- "NAME": a string value used to name the exported data if the export format is XML

`model` : | a GdaDataModel
`format` : | the format in which to export data
`cols` : | an array containing which columns of `model` will be exported, or `NULL` for all columns
`nb_cols` : | the number of columns in `cols`
`rows` : | an array containing which rows of `model` will be exported, or `NULL` for all rows
`nb_rows` : | the number of rows in `rows`
`options` : | list of options for the export
Returns : | a new string.

### gda_data_model_export_to_file ()

    gboolean            gda_data_model_export_to_file       (GdaDataModel *model,
                                                             GdaDataModelIOFormat format,
                                                             const gchar *file,
                                                             const gint *cols,
                                                             gint nb_cols,
                                                             const gint *rows,
                                                             gint nb_rows,
                                                             GdaParameterList *options,
                                                             GError **error);

Exports data contained in `model` to the `file` file; the format is specified using the `format` argument.

Specifically, the parameters in the `options` list can be:

- "SEPARATOR": a string value of which the first character is used as a separator in case of CSV export

- "NAME": a string value used to name the exported data if the export format is XML

- "OVERWRITE": a boolean value which tells if the file must be over-written if it already exists.

`model` : | a GdaDataModel
`format` : | the format in which to export data
`file` : | the filename to export to
`cols` : | an array containing which columns of `model` will be exported, or `NULL` for all columns
`nb_cols` : | the number of columns in `cols`
`rows` : | an array containing which rows of `model` will be exported, or `NULL` for all rows
`nb_rows` : | the number of rows in `rows`
`options` : | list of options for the export
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if no error occurred

### gda_data_model_add_data_from_xml_node ()

    gboolean            gda_data_model_add_data_from_xml_node
                                                            (GdaDataModel *model,
                                                             xmlNodePtr node,
                                                             GError **error);

Adds the data from a XML node to the given data model (see the DTD for that node in the $prefix/share/libgda/dtd/libgda-array.dtd file).

`model` : | a GdaDataModel.
`node` : | a XML node representing a <gda_array_data> XML node.
`error` : |
Returns : | `TRUE` if successful, `FALSE` otherwise.

### gda_data_model_import_from_model ()

    gboolean            gda_data_model_import_from_model    (GdaDataModel *to,
                                                             GdaDataModel *from,
                                                             gboolean overwrite,
                                                             GHashTable *cols_trans,
                                                             GError **error);

Copy the contents of the `from` data model to the `to` data model. The copy stops as soon as an error orrurs.

The `cols_trans` is a hash table for which keys are `to` columns numbers and the values are the corresponding column numbers in the `from` data model. To set the values of a column in `to` to NULL, create an entry in the hash table with a negative value.

`to` : | the destination GdaDataModel
`from` : | the source GdaDataModel
`overwrite` : | TRUE if `to` is completely overwritten by `from`'s data, and FALSE if `from`'s data is appended to `to`
`cols_trans` : | a GHashTable for columns translating, or `NULL`
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if no error occurred.

### gda_data_model_import_from_string ()

    gboolean            gda_data_model_import_from_string   (GdaDataModel *model,
                                                             const gchar *string,
                                                             GHashTable *cols_trans,
                                                             GdaParameterList *options,
                                                             GError **error);

Loads the data from `string` into `model`.

`model` : | a GdaDataModel
`string` : | the string to import data from
`cols_trans` : | a hash table containing which columns of `model` will be imported, or `NULL` for all columns
`options` : | list of options for the export
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if no error occurred.

### gda_data_model_import_from_file ()

    gboolean            gda_data_model_import_from_file     (GdaDataModel *model,
                                                             const gchar *file,
                                                             GHashTable *cols_trans,
                                                             GdaParameterList *options,
                                                             GError **error);

Imports data contained in the `file` file into `model`; the format is detected.

`model` : | a GdaDataModel
`file` : | the filename to import from
`cols_trans` : | a GHashTable for columns translating, or `NULL`
`options` : | list of options for the export
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if no error occurred

### gda_data_model_dump ()

    void                gda_data_model_dump                 (GdaDataModel *model,
                                                             FILE *to_stream);

Dumps a textual representation of the `model` to the `to_stream` stream

`model` : | a GdaDataModel.
`to_stream` : | where to dump the data model

### gda_data_model_dump_as_string ()

    gchar*              gda_data_model_dump_as_string       (GdaDataModel *model);

Dumps a textual representation of the `model` into a new string

`model` : | a GdaDataModel.
Returns : | a new string.

## Signal Details

### The "reset" signal

    void                user_function                      (GdaDataModel *gdadatamodel,
                                                            gpointer      user_data)         : Run Last

`gdadatamodel` : | the object which received the signal.
`user_data` : | user data set when the signal handler was connected.

### The "row-inserted" signal

    void                user_function                      (GdaDataModel *gdadatamodel,
                                                            gint          arg1,
                                                            gpointer      user_data)         : Run Last

`gdadatamodel` : | the object which received the signal.
`arg1` : |
`user_data` : | user data set when the signal handler was connected.

### The "row-removed" signal

    void                user_function                      (GdaDataModel *gdadatamodel,
                                                            gint          arg1,
                                                            gpointer      user_data)         : Run Last

`gdadatamodel` : | the object which received the signal.
`arg1` : |
`user_data` : | user data set when the signal handler was connected.

### The "row-updated" signal

    void                user_function                      (GdaDataModel *gdadatamodel,
                                                            gint          arg1,
                                                            gpointer      user_data)         : Run Last

`gdadatamodel` : | the object which received the signal.
`arg1` : |
`user_data` : | user data set when the signal handler was connected.