# wx.dataview.DataViewModel¶

wx.dataview.DataViewModel is the base class for all data model to be displayed by a wx.dataview.DataViewCtrl.

All other models derive from it and must implement its pure virtual functions in order to define a complete data model. In detail, you need to override wx.dataview.DataViewModel.IsContainer , wx.dataview.DataViewModel.GetParent , wx.dataview.DataViewModel.GetChildren , wx.dataview.DataViewModel.GetColumnCount , wx.dataview.DataViewModel.GetColumnType and wx.dataview.DataViewModel.GetValue in order to define the data model which acts as an interface between your actual data and the wx.dataview.DataViewCtrl.

Note that wx.dataview.DataViewModel does not define the position or index of any item in the control because different controls might display the same data differently. wx.dataview.DataViewModel does provide a wx.dataview.DataViewModel.Compare method which the wx.dataview.DataViewCtrl may use to sort the data either in conjunction with a column header or without (see wx.dataview.DataViewModel.HasDefaultCompare ).

wx.dataview.DataViewModel (as indeed the entire wx.dataview.DataViewCtrl code) is using Variant to store data and its type in a generic way. Variant can be extended to contain almost any data without changes to the original class. To a certain extent, you can use (the somewhat more elegant) Any instead of Variant as there is code to convert between the two, but it is unclear what impact this will have on performance.

Since you will usually allow the wx.dataview.DataViewCtrl to change your data through its graphical interface, you will also have to override wx.dataview.DataViewModel.SetValue which the wx.dataview.DataViewCtrl will call when a change to some data has been committed.

If the data represented by the model is changed by something else than its associated wx.dataview.DataViewCtrl, the control has to be notified about the change. Depending on what happened you need to call one of the following methods:

There are plural forms for notification of addition, change or removal of several item at once. See:

Note that Cleared can be called for all changes involving many, or all, of the model items and not only for deleting all of them (i.e. clearing the model).

This class maintains a list of wx.dataview.DataViewModelNotifier which link this class to the specific implementations on the supported platforms so that e.g. calling wx.dataview.DataViewModel.ValueChanged on this model will just call wx.dataview.DataViewModelNotifier.ValueChanged for each notifier that has been added. You can also add your own notifier in order to get informed about any changes to the data in the list model.

Currently wxWidgets provides the following models apart from the base model: wx.dataview.DataViewIndexListModel, wx.dataview.DataViewVirtualListModel, wx.dataview.DataViewTreeStore, wx.dataview.DataViewListStore.

Note that wx.dataview.DataViewModel is reference counted, derives from wx.RefCounter and cannot be deleted directly as it can be shared by several DataViewCtrls. This implies that you need to decrease the reference count after associating the model with a control like this:

musicCtrl = wx.dataview.DataViewCtrl(self, wx.ID_ANY)
musicModel = MyMusicModel()
musicCtrl.AssociateModel(musicModel)
musicModel.DecRef()  # avoid memory leak !!



A potentially better way to avoid memory leaks is to use ObjectDataPtr

### wxPython does not provide wrappers for wxObjectDataPtr


## Class Hierarchy¶

Inheritance diagram for class DataViewModel:

## Methods Summary¶

 __init__ Constructor. AddNotifier Adds a wx.dataview.DataViewModelNotifier to the model. ChangeValue Change the value of the given item and update the control to reflect it. Cleared Called to inform the model that all of its data has been changed. Compare The compare function to be used by the control. GetAttr Override this to indicate that the item has special font attributes. GetChildren Override this so the control can query the child items of an item. GetColumnCount Override this to indicate the number of columns in the model. GetColumnType Override this to indicate what type of data is stored in the column specified by col. GetParent Override this to indicate which wx.dataview.DataViewItem representing the parent of item or an invalid wx.dataview.DataViewItem if the root item is the parent item. GetValue Override this to indicate the value of item. HasContainerColumns Override this method to indicate if a container item merely acts as a headline (or for categorisation) or if it also acts a normal item with entries for further columns. HasDefaultCompare Override this to indicate that the model provides a default compare function that the control should use if no wx.dataview.DataViewColumn has been chosen for sorting. HasValue Return True if there is a value in the given column of this item. IsContainer Override this to indicate of item is a container, i.e. if it can have child items. IsEnabled Override this to indicate that the item should be disabled. IsListModel IsVirtualListModel ItemAdded Call this to inform the model that an item has been added to the data. ItemChanged Call this to inform the model that an item has changed. ItemDeleted Call this to inform the model that an item has been deleted from the data. ItemsAdded Call this to inform the model that several items have been added to the data. ItemsChanged Call this to inform the model that several items have changed. ItemsDeleted Call this to inform the model that several items have been deleted. RemoveNotifier Remove the notifier from the list of notifiers. Resort Call this to initiate a resort after the sort function has been changed. SetValue This gets called in order to set a value in the data model. ValueChanged Call this to inform this model that a value in the model has been changed. ~wxDataViewModel Destructor.

## Class API¶

class wx.dataview.DataViewModel(RefCounter)

Possible constructors:

DataViewModel()


DataViewModel is the base class for all data model to be displayed by a DataViewCtrl.

### Methods¶

__init__(self)

Constructor.

AddNotifier(self, notifier)

Adds a wx.dataview.DataViewModelNotifier to the model.

Parameters

notifier (wx.dataview.DataViewModelNotifier) –

ChangeValue(self, variant, item, col)

Change the value of the given item and update the control to reflect it.

This function simply calls SetValue and, if it succeeded, ValueChanged .

Parameters
• variant (DVCVariant) – The new value.

• item (wx.dataview.DataViewItem) – The item (row) to update.

• col (int) – The column to update.

Return type

bool

Returns

True if both SetValue and ValueChanged returned True.

New in version 2.9.1.

Cleared(self)

Called to inform the model that all of its data has been changed.

This method should be called if so many of the model items have changed, that the control should just reread all of them, repopulating itself entirely.

Note that, contrary to the name of the method, it doesn’t necessarily indicate that model has become empty – although this is the right method to call, rather than ItemsDeleted , if it was indeed cleared, which explains the origin of its name.

Return type

bool

Compare(self, item1, item2, column, ascending)

The compare function to be used by the control.

The default compare function sorts most data types implemented by Variant (i.e. bool, int, long, double, string) as well as datetime and wx.dataview.DataViewIconText. Override this method to implement a different sorting behaviour or override just DoCompareValues to extend it to support other Variant types.

The function should return negative, null or positive for an ascending comparison, depending on whether the first item is less than, equal to or greater than the second one. The reverse is True for descending comparisons. The items should be compared using the appropriate type for the column passed.

Parameters
• item1 (wx.dataview.DataViewItem) – First item to compare.

• item2 (wx.dataview.DataViewItem) – Second item to compare.

• column (int) – The column holding the items to be compared. If the model class overrides HasDefaultCompare to return True, this parameter will be

• ascending (bool) – Indicates whether the sort is being performed in ascending or descending order.

Return type

int

Returns

For an ascending comparison: a negative value if the item1 is less than (i.e. should appear above) item2, zero if the two items are equal or a positive value if item1 is greater than (i.e. should appear below) the second one. The reverse for a descending comparison.

Note

If there can be multiple rows with the same value, consider differentiating them form each other by their IDs rather than returning zero. This to prevent rows with the same value jumping positions when items are added etc. For example:

obj1 = self.ItemToObject(item1)
obj2 = self.ItemToObject(item2)
if obj1[column] == obj2[column]:
return 1 if ascending == (item1.GetId() > item2.GetId()) else -1
else:
return 1 if ascending == (obj1[column] > obj2[column]) else -1


HasDefaultCompare , DoCompareValues

GetAttr(self, item, col, attr)

Override this to indicate that the item has special font attributes.

This only affects the DataViewTextRendererText renderer.

The base class version always simply returns False.

Parameters
• item (wx.dataview.DataViewItem) – The item for which the attribute is requested.

• col (int) – The column of the item for which the attribute is requested.

• attr (wx.dataview.DataViewItemAttr) – The attribute to be filled in if the function returns True.

Return type

bool

Returns

True if this item has an attribute or False otherwise.

GetChildren(self, item, children)

Override this so the control can query the child items of an item.

Returns the number of items.

Parameters
Return type

int

GetColumnCount(self)

Override this to indicate the number of columns in the model.

Return type

int

GetColumnType(self, col)

Override this to indicate what type of data is stored in the column specified by col.

This should return a string indicating the type of data as reported by Variant .

Parameters

col (int) –

Return type

string

GetParent(self, item)

Override this to indicate which wx.dataview.DataViewItem representing the parent of item or an invalid wx.dataview.DataViewItem if the root item is the parent item.

Parameters

item (wx.dataview.DataViewItem) –

Return type

wx.dataview.DataViewItem

GetValue(self, item, col)

Override this to indicate the value of item.

A Variant is used to store the data.

Parameters
Return type

variant

HasContainerColumns(self, item)

Override this method to indicate if a container item merely acts as a headline (or for categorisation) or if it also acts a normal item with entries for further columns.

By default returns False.

Parameters

item (wx.dataview.DataViewItem) –

Return type

bool

HasDefaultCompare(self)

Override this to indicate that the model provides a default compare function that the control should use if no wx.dataview.DataViewColumn has been chosen for sorting.

Usually, the user clicks on a column header for sorting, the data will be sorted alphanumerically.

If any other order (e.g. by index or order of appearance) is required, then this should be used.

Note that if this method is overridden to return True, the implementation of Compare should be ready to accept

See wx.dataview.DataViewIndexListModel for a model which makes use of this.

Return type

bool

HasValue(self, item, col)

Return True if there is a value in the given column of this item.

All normal items have values in all columns but the container items only show their label in the first column (col == 0) by default (but see HasContainerColumns ). So this function by default returns True for the first column while for the other ones it returns True only if the item is not a container or HasContainerColumns was overridden to return True for it.

Since wxWidgets 3.1.4, this method is virtual and can be overridden to explicitly specify for which columns a given item has, and doesn’t have, values.

Parameters
Return type

bool

New in version 2.9.1.

IsContainer(self, item)

Override this to indicate of item is a container, i.e. if it can have child items.

Parameters

item (wx.dataview.DataViewItem) –

Return type

bool

IsEnabled(self, item, col)

Override this to indicate that the item should be disabled.

Disabled items are displayed differently (e.g. grayed out) and cannot be interacted with.

The base class version always returns True, thus making all items enabled by default.

Parameters
• item (wx.dataview.DataViewItem) – The item whose enabled status is requested.

• col (int) – The column of the item whose enabled status is requested.

Return type

bool

Returns

True if this item should be enabled, False otherwise.

New in version 2.9.2.

IsListModel(self)
Return type

bool

IsVirtualListModel(self)
Return type

bool

ItemAdded(self, parent, item)

Call this to inform the model that an item has been added to the data.

Parameters
Return type

bool

ItemChanged(self, item)

Call this to inform the model that an item has changed.

This will eventually emit a wxEVT_DATAVIEW_ITEM_VALUE_CHANGED event (in which the column fields will not be set) to the user.

Parameters

item (wx.dataview.DataViewItem) –

Return type

bool

ItemDeleted(self, parent, item)

Call this to inform the model that an item has been deleted from the data.

Parameters
Return type

bool

ItemsAdded(self, parent, items)

Call this to inform the model that several items have been added to the data.

Parameters
Return type

bool

ItemsChanged(self, items)

Call this to inform the model that several items have changed.

This will eventually emit wxEVT_DATAVIEW_ITEM_VALUE_CHANGED events (in which the column fields will not be set) to the user.

Parameters

items (DataViewItemArray) –

Return type

bool

ItemsDeleted(self, parent, items)

Call this to inform the model that several items have been deleted.

Parameters
Return type

bool

RemoveNotifier(self, notifier)

Remove the notifier from the list of notifiers.

Parameters

notifier (wx.dataview.DataViewModelNotifier) –

Resort(self)

Call this to initiate a resort after the sort function has been changed.

SetValue(self, variant, item, col)

This gets called in order to set a value in the data model.

The most common scenario is that the wx.dataview.DataViewCtrl calls this method after the user changed some data in the view.

This is the function you need to override in your derived class but if you want to call it, ChangeValue is usually more convenient as otherwise you need to manually call ValueChanged to update the control itself.

Parameters
Return type

bool

ValueChanged(self, item, col)

Call this to inform this model that a value in the model has been changed.

This is also called from wx.dataview.DataViewCtrl’s internal editing code, e.g. when editing a text field in the control.

This will eventually emit a wxEVT_DATAVIEW_ITEM_VALUE_CHANGED event to the user.

Parameters
Return type

bool

~wxDataViewModel(self)

Destructor.

This should not be called directly. Use DecRef instead.

### Properties¶

ColumnCount