QItemModelBarDataProxy Class▲
-
Header: QItemModelBarDataProxy
-
Since: QtDataVisualization 1.0
-
CMake:
find_package(Qt6 REQUIRED COMPONENTS DataVisualization)
target_link_libraries(mytarget PRIVATE Qt6::DataVisualization)
-
qmake: QT += datavisualization
-
Inherited By:
-
Instantiated By: qml-qtdatavisualization-itemmodelbardataproxy.xml
-
Inherits: QBarDataProxy
Detailed Description▲
QItemModelBarDataProxy allows you to use QAbstractItemModel derived models as a data source for Q3DBars. It uses the defined mappings to map data from the model to rows, columns, and values of Q3DBars graph.
The data is resolved asynchronously whenever mappings or the model changes. QBarDataProxy::arrayReset() is emitted when the data has been resolved. However, when useModelCategories property is set to true, single item changes are resolved synchronously, unless the same frame also contains a change that causes the whole model to be resolved.
Mappings can be used in the following ways:
-
If useModelCategories property is set to true, this proxy will map rows and columns of QAbstractItemModel directly to rows and columns of Q3DBars, and uses the value returned for Qt::DisplayRole as bar value by default. The value role to be used can be redefined if Qt::DisplayRole is not suitable.
-
For models that do not have data already neatly sorted into rows and columns, such as QAbstractListModel based models, you can define a role from the model to map for each of row, column and value.
-
If you do not want to include all data contained in the model, or the autogenerated rows and columns are not ordered as you wish, you can specify which rows and columns should be included and in which order by defining an explicit list of categories for either or both of rows and columns.
For example, assume that you have a custom QAbstractItemModel for storing various monthly values related to a business. Each item in the model has the roles "year", "month", "income", and "expenses". You could do the following to display the data in a bar graph:
// By defining row and column categories, you tell the mapping which row and column each item
// belongs to. The categories must match the data stored in the model in the roles you define
// for row and column mapping. In this example we expect "year" role to return four digit year
// and "month" to return three letter designation for the month.
//
// An example of an item in model would be:
// Requested role -> Returned data
// "year" -> "2006" // Matches the first row category, so this item is added to the first row.
// "month" -> "jan" // Matches the first column category, so this item is added as first item in the row.
// "income" -> "12.1"
// "expenses" -> "9.2"
QStringList years;
QStringList months;
years << "2006" << "2007" << "2008" << "2009" << "2010" << "2011" << "2012";
months << "jan" << "feb" << "mar" << "apr" << "may" << "jun" << "jul" << "aug" << "sep" << "oct" << "nov" << "dec";
QItemModelBarDataProxy *proxy = new QItemModelBarDataProxy(customModel,
QStringLiteral("year"), // Row role
QStringLiteral("month"), // Column role
QStringLiteral("income"), // Value role
years, // Row categories
months); // Column categories
//...
// To display different data later, you can simply change the mapping.
proxy->setValueRole(QStringLiteral("expenses"));If the fields of the model do not contain the data in the exact format you need, you can specify a search pattern regular expression and a replace rule for each role to get the value in a format you need. For more information how the replace using regular expressions works, see QString::replace(const QRegularExpression &rx, const QString &after) function documentation. Note that using regular expressions has an impact on the performance, so it's more efficient to utilize item models where doing search and replace is not necessary to get the desired values.
For example about using the search patterns in conjunction with the roles, see Qt Quick 2 Bars Example.
See Also▲
See also Qt Data Visualization Data Handling
Member Type Documentation▲
enum QItemModelBarDataProxy::MultiMatchBehavior▲
Behavior types for QItemModelBarDataProxy::multiMatchBehavior property.
|
Constant |
Value |
Description |
|---|---|---|
|
QItemModelBarDataProxy::MMBFirst |
0 |
The value is taken from the first item in the item model that matches each row/column combination. |
|
QItemModelBarDataProxy::MMBLast |
1 |
The value is taken from the last item in the item model that matches each row/column combination. |
|
QItemModelBarDataProxy::MMBAverage |
2 |
The values from all items matching each row/column combination are averaged together and the average is used as the bar value. |
|
QItemModelBarDataProxy::MMBCumulative |
3 |
The values from all items matching each row/column combination are added together and the total is used as the bar value. |
Property Documentation▲
autoColumnCategories : bool▲
This property holds whether column categories are generated automatically.
When set to true, the mapping ignores any explicitly set column categories and overwrites them with automatically generated ones whenever the data from model is resolved. Defaults to true.
Access functions:
-
bool autoColumnCategories() const
-
void setAutoColumnCategories(bool enable)
Notifier signal:
-
void autoColumnCategoriesChanged(bool enable)
autoRowCategories : bool▲
This property holds whether row categories are generated automatically.
When set to true, the mapping ignores any explicitly set row categories and overwrites them with automatically generated ones whenever the data from model is resolved. Defaults to true.
Access functions:
-
bool autoRowCategories() const
-
void setAutoRowCategories(bool enable)
Notifier signal:
-
void autoRowCategoriesChanged(bool enable)
columnCategories : QStringList▲
This property holds the column categories for the mapping.
Access functions:
-
columnCategories() const
-
void setColumnCategories(const &categories)
Notifier signal:
-
void columnCategoriesChanged()
columnRole : QString▲
This property holds the column role for the mapping.
Access functions:
-
columnRole() const
-
void setColumnRole(const &role)
Notifier signal:
-
void columnRoleChanged(const &role)
columnRolePattern : QRegularExpression▲
This property holds whether a search and replace is done on the value mapped by column role before it is used as a column category.
This property specifies the regular expression to find the portion of the mapped value to replace and columnRoleReplace property contains the replacement string. This is useful for example in parsing row and column categories from a single timestamp field in the item model.
Access functions:
-
columnRolePattern() const
-
void setColumnRolePattern(const &pattern)
Notifier signal:
-
void columnRolePatternChanged(const &pattern)
See Also▲
See also columnRole, columnRoleReplace
columnRoleReplace : QString▲
This property holds the replace content to be used in conjunction with columnRolePattern.
Defaults to empty string. For more information on how the search and replace using regular expressions works, see QString::replace(const QRegularExpression &rx, const QString &after) function documentation.
Access functions:
-
columnRoleReplace() const
-
void setColumnRoleReplace(const &replace)
Notifier signal:
-
void columnRoleReplaceChanged(const &replace)
See Also▲
See also columnRole, columnRolePattern
itemModel : QAbstractItemModel*▲
This property holds the item model.
Access functions:
-
*itemModel() const
-
void setItemModel( *itemModel)
Notifier signal:
-
void itemModelChanged(const *itemModel)
multiMatchBehavior : MultiMatchBehavior▲
How multiple matches for each row/column combination are handled.
Defaults to QItemModelBarDataProxy::MMBLast. The chosen behavior affects both bar value and rotation.
For example, you might have an item model with timestamped data taken at irregular intervals and you want to visualize total value of data items on each day with a bar graph. This can be done by specifying row and column categories so that each bar represents a day, and setting multiMatchBehavior to QItemModelBarDataProxy::MMBCumulative.
Access functions:
-
multiMatchBehavior() const
-
void setMultiMatchBehavior( behavior)
Notifier signal:
-
void multiMatchBehaviorChanged( behavior)
rotationRole : QString▲
This property holds the rotation role for the mapping.
Access functions:
-
rotationRole() const
-
void setRotationRole(const &role)
Notifier signal:
-
void rotationRoleChanged(const &role)
rotationRolePattern : QRegularExpression▲
This property holds whether a search and replace is done on the value mapped by rotation role before it is used as a bar rotation angle.
This property specifies the regular expression to find the portion of the mapped value to replace and rotationRoleReplace property contains the replacement string.
Access functions:
-
rotationRolePattern() const
-
void setRotationRolePattern(const &pattern)
Notifier signal:
-
void rotationRolePatternChanged(const &pattern)
See Also▲
See also rotationRole, rotationRoleReplace
rotationRoleReplace : QString▲
This property holds the replace content to be used in conjunction with rotationRolePattern.
Defaults to empty string. For more information on how the search and replace using regular expressions works, see QString::replace(const QRegularExpression &rx, const QString &after) function documentation.
Access functions:
-
rotationRoleReplace() const
-
void setRotationRoleReplace(const &replace)
Notifier signal:
-
void rotationRoleReplaceChanged(const &replace)
See Also▲
See also rotationRole, rotationRolePattern
rowCategories : QStringList▲
This property holds the row categories for the mapping.
Access functions:
-
rowCategories() const
-
void setRowCategories(const &categories)
Notifier signal:
-
void rowCategoriesChanged()
rowRole : QString▲
This property holds the row role for the mapping.
Access functions:
-
rowRole() const
-
void setRowRole(const &role)
Notifier signal:
-
void rowRoleChanged(const &role)
rowRolePattern : QRegularExpression▲
This property holds whether a search and replace is performed on the value mapped by row role before it is used as a row category.
This property specifies the regular expression to find the portion of the mapped value to replace and rowRoleReplace property contains the replacement string. This is useful for example in parsing row and column categories from a single timestamp field in the item model.
Access functions:
-
rowRolePattern() const
-
void setRowRolePattern(const &pattern)
Notifier signal:
-
void rowRolePatternChanged(const &pattern)
See Also▲
See also rowRole, rowRoleReplace
rowRoleReplace : QString▲
This property holds the replace content to be used in conjunction with rowRolePattern.
Defaults to empty string. For more information on how the search and replace using regular expressions works, see QString::replace(const QRegularExpression &rx, const QString &after) function documentation.
Access functions:
-
rowRoleReplace() const
-
void setRowRoleReplace(const &replace)
Notifier signal:
-
void rowRoleReplaceChanged(const &replace)
See Also▲
See also rowRole, rowRolePattern
useModelCategories : bool▲
This property holds whether row and column roles and categories are used for mapping.
When set to true, the mapping ignores row and column roles and categories, and uses the rows and columns from the model instead. Defaults to false.
Access functions:
-
bool useModelCategories() const
-
void setUseModelCategories(bool enable)
Notifier signal:
-
void useModelCategoriesChanged(bool enable)
valueRole : QString▲
This property holds the value role for the mapping.
Access functions:
-
valueRole() const
-
void setValueRole(const &role)
Notifier signal:
-
void valueRoleChanged(const &role)
valueRolePattern : QRegularExpression▲
This property holds whether a search and replace is done on the value mapped by value role before it is used as a bar value.
This property specifies the regular expression to find the portion of the mapped value to replace and valueRoleReplace property contains the replacement string.
Access functions:
-
valueRolePattern() const
-
void setValueRolePattern(const &pattern)
Notifier signal:
-
void valueRolePatternChanged(const &pattern)
See Also▲
See also valueRole, valueRoleReplace
valueRoleReplace : QString▲
This property holds the replace content to be used in conjunction with valueRolePattern.
Defaults to empty string. For more information on how the search and replace using regular expressions works, see QString::replace(const QRegularExpression &rx, const QString &after) function documentation.
Access functions:
-
valueRoleReplace() const
-
void setValueRoleReplace(const &replace)
Notifier signal:
-
void valueRoleReplaceChanged(const &replace)
See Also▲
See also valueRole, valueRolePattern
Member Function Documentation▲
[explicit] QItemModelBarDataProxy::QItemModelBarDataProxy(QObject *parent = nullptr)▲
Constructs QItemModelBarDataProxy with optional parent.
[explicit] QItemModelBarDataProxy::QItemModelBarDataProxy(QAbstractItemModel *itemModel, QObject *parent = nullptr)▲
Constructs QItemModelBarDataProxy with itemModel and optional parent. Proxy doesn't take ownership of the itemModel, as typically item models are owned by other controls.
[explicit] QItemModelBarDataProxy::QItemModelBarDataProxy(QAbstractItemModel *itemModel, const QString &valueRole, QObject *parent = nullptr)▲
Constructs QItemModelBarDataProxy with itemModel and optional parent. Proxy doesn't take ownership of the itemModel, as typically item models are owned by other controls. The value role is set to valueRole. This constructor is meant to be used with models that have data properly sorted in rows and columns already, so it also sets useModelCategories property to true.
[explicit] QItemModelBarDataProxy::QItemModelBarDataProxy(QAbstractItemModel *itemModel, const QString &rowRole, const QString &columnRole, const QString &valueRole, QObject *parent = nullptr)▲
Constructs QItemModelBarDataProxy with itemModel and optional parent. Proxy doesn't take ownership of the itemModel, as typically item models are owned by other controls. The role mappings are set with rowRole, columnRole, and valueRole.
[explicit] QItemModelBarDataProxy::QItemModelBarDataProxy(QAbstractItemModel *itemModel, const QString &rowRole, const QString &columnRole, const QString &valueRole, const QString &rotationRole, QObject *parent = nullptr)▲
Constructs QItemModelBarDataProxy with itemModel and optional parent. Proxy doesn't take ownership of the itemModel, as typically item models are owned by other controls. The role mappings are set with rowRole, columnRole, valueRole, and rotationRole.
[explicit] QItemModelBarDataProxy::QItemModelBarDataProxy(QAbstractItemModel *itemModel, const QString &rowRole, const QString &columnRole, const QString &valueRole, const QStringList &rowCategories, const QStringList &columnCategories, QObject *parent = nullptr)▲
Constructs QItemModelBarDataProxy with itemModel and optional parent. Proxy doesn't take ownership of the itemModel, as typically item models are owned by other controls. The role mappings are set with rowRole, columnRole, and valueRole. Row and column categories are set with rowCategories and columnCategories. This constructor also sets autoRowCategories and autoColumnCategories to false.
[explicit] QItemModelBarDataProxy::QItemModelBarDataProxy(QAbstractItemModel *itemModel, const QString &rowRole, const QString &columnRole, const QString &valueRole, const QString &rotationRole, const QStringList &rowCategories, const QStringList &columnCategories, QObject *parent = nullptr)▲
Constructs QItemModelBarDataProxy with itemModel and optional parent. Proxy doesn't take ownership of the itemModel, as typically item models are owned by other controls. The role mappings are set with rowRole, columnRole, valueRole, and rotationRole. Row and column categories are set with rowCategories and columnCategories. This constructor also sets autoRowCategories and autoColumnCategories to false.
[virtual] QItemModelBarDataProxy::~QItemModelBarDataProxy()▲
Destroys QItemModelBarDataProxy.
int QItemModelBarDataProxy::columnCategoryIndex(const QString &category)▲
Returns the index of the specified category in column categories list. If the category is not found, -1 is returned.
If the automatic column categories generation is in use, this method will not return a valid index before the data in the model is resolved for the first time.
void QItemModelBarDataProxy::remap(const QString &rowRole, const QString &columnRole, const QString &valueRole, const QString &rotationRole, const QStringList &rowCategories, const QStringList &columnCategories)▲
Changes rowRole, columnRole, valueRole, rotationRole, rowCategories and columnCategories to the mapping.
int QItemModelBarDataProxy::rowCategoryIndex(const QString &category)▲
Returns the index of the specified category in row categories list. If the row categories list is empty, -1 is returned.
If the automatic row categories generation is in use, this method will not return a valid index before the data in the model is resolved for the first time.