QGIS API Documentation 3.41.0-Master (3c143d501a8)
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The QgsFieldExpressionWidget class creates a widget to choose fields and edit expressions It contains a combo box to display the fields and expression and a button to open the expression dialog. More...
#include <qgsfieldexpressionwidget.h>
Public Slots | |
void | setExpression (const QString &expression) |
Sets the current expression text and if applicable also the field. | |
void | setField (const QString &fieldName) |
sets the current field or expression in the widget | |
void | setFields (const QgsFields &fields) |
Sets the fields used in the widget to fields, this allows the widget to work without a layer. | |
void | setLayer (QgsMapLayer *layer) |
Sets the layer used to display the fields and expression. | |
void | setRow (int row) |
sets the current row in the widget | |
Signals | |
void | allowEvalErrorsChanged () |
Allow accepting expressions with evaluation errors. | |
void | buttonVisibleChanged () |
Emitted when the button visibility changes. | |
void | fieldChanged (const QString &fieldName) |
Emitted when the currently selected field changes. | |
void | fieldChanged (const QString &fieldName, bool isValid) |
fieldChanged signal with indication of the validity of the expression | |
Public Member Functions | |
QgsFieldExpressionWidget (QWidget *parent=nullptr) | |
QgsFieldExpressionWidget creates a widget with a combo box to display the fields and expression and a button to open the expression dialog. | |
bool | allowEmptyFieldName () const |
Returns true if the combo box allows the empty field ("not set") choice. | |
bool | allowEvalErrors () const |
Allow accepting expressions with evaluation errors. | |
void | appendScope (QgsExpressionContextScope *scope) |
Appends a scope to the current expression context. | |
QString | asExpression () const |
Returns the currently selected field or expression. | |
bool | buttonVisible () const |
Returns the visibility of the button. | |
QString | currentField (bool *isExpression=nullptr, bool *isValid=nullptr) const |
currentField returns the currently selected field or expression if allowed | |
QString | currentText () const |
Returns the current text that is set in the expression area. | |
QString | expression () const |
Returns the currently selected field or expression. | |
const QString | expressionDialogTitle () |
Returns the title used for the expression dialog. | |
QgsFieldProxyModel::Filters | filters () const |
currently used filter on list of fields | |
bool | isExpression () const |
If the content is not just a simple field this method will return true . | |
bool | isValidExpression (QString *expressionError=nullptr) const |
Returns true if the current expression is valid. | |
QgsVectorLayer * | layer () const |
Returns the layer currently associated with the widget. | |
void | registerExpressionContextGenerator (const QgsExpressionContextGenerator *generator) |
Register an expression context generator class that will be used to retrieve an expression context for the widget. | |
void | setAllowEmptyFieldName (bool allowEmpty) |
Sets whether an optional empty field ("not set") option is shown in the combo box. | |
void | setAllowEvalErrors (bool allowEvalErrors) |
Allow accepting expressions with evaluation errors. | |
void | setButtonVisible (bool visible) |
Set the visibility of the button. | |
void | setCustomPreviewGenerator (const QString &label, const QList< QPair< QString, QVariant > > &choices, const std::function< QgsExpressionContext(const QVariant &) > &previewContextGenerator) |
Sets the widget to run using a custom preview generator. | |
void | setExpressionDialogTitle (const QString &title) |
define the title used in the expression dialog | |
void | setFilters (QgsFieldProxyModel::Filters filters) |
setFilters allows filtering according to the type of field | |
void | setGeomCalculator (const QgsDistanceArea &da) |
Sets the geometry calculator used in the expression dialog. | |
void | setLeftHandButtonStyle (bool isLeft) |
Protected Slots | |
void | currentFieldChanged () |
void | editExpression () |
open the expression dialog to edit the current or add a new expression | |
void | expressionEdited (const QString &expression) |
when expression is edited by the user in the line edit, it will be checked for validity | |
void | expressionEditingFinished () |
when expression has been edited (finished) it will be added to the model | |
bool | isExpressionValid (const QString &expressionStr) |
void | updateLineEditStyle (const QString &expression=QString()) |
updateLineEditStyle will re-style (color/font) the line edit depending on content and status | |
Protected Member Functions | |
void | changeEvent (QEvent *event) override |
bool | eventFilter (QObject *watched, QEvent *event) override |
Properties | |
bool | allowEmptyFieldName |
bool | allowEvalErrors |
bool | buttonVisible |
QString | expressionDialogTitle |
QgsFieldProxyModel::Filters | filters |
Friends | |
class | TestQgsFieldExpressionWidget |
The QgsFieldExpressionWidget class creates a widget to choose fields and edit expressions It contains a combo box to display the fields and expression and a button to open the expression dialog.
The combo box is editable, allowing expressions to be edited inline. The validity of the expression is checked live on key press, invalid expressions are displayed in red. The expression will be added to the model (and the fieldChanged signals emitted) only when editing in the line edit is finished (focus lost, enter key pressed).
Definition at line 46 of file qgsfieldexpressionwidget.h.
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explicit |
QgsFieldExpressionWidget creates a widget with a combo box to display the fields and expression and a button to open the expression dialog.
Definition at line 33 of file qgsfieldexpressionwidget.cpp.
bool QgsFieldExpressionWidget::allowEmptyFieldName | ( | ) | const |
Returns true
if the combo box allows the empty field ("not set") choice.
Definition at line 89 of file qgsfieldexpressionwidget.cpp.
bool QgsFieldExpressionWidget::allowEvalErrors | ( | ) | const |
Allow accepting expressions with evaluation errors.
This can be useful when we are not able to provide an expression context of which we are sure it's completely populated.
Definition at line 324 of file qgsfieldexpressionwidget.cpp.
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signal |
Allow accepting expressions with evaluation errors.
This can be useful when we are not able to provide an expression context of which we are sure it's completely populated.
void QgsFieldExpressionWidget::appendScope | ( | QgsExpressionContextScope * | scope | ) |
Appends a scope to the current expression context.
scope | The scope to add. |
Definition at line 414 of file qgsfieldexpressionwidget.cpp.
QString QgsFieldExpressionWidget::asExpression | ( | ) | const |
Returns the currently selected field or expression.
If a field is currently selected, the returned value will be converted to a valid expression referencing this field (ie enclosing the field name with appropriate quotations).
Definition at line 119 of file qgsfieldexpressionwidget.cpp.
bool QgsFieldExpressionWidget::buttonVisible | ( | ) | const |
Returns the visibility of the button.
If button is hidden, the widget essentially becomes an editable combo box
Definition at line 339 of file qgsfieldexpressionwidget.cpp.
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signal |
Emitted when the button visibility changes.
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overrideprotected |
Definition at line 285 of file qgsfieldexpressionwidget.cpp.
QString QgsFieldExpressionWidget::currentField | ( | bool * | isExpression = nullptr , |
bool * | isValid = nullptr |
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) | const |
currentField returns the currently selected field or expression if allowed
isExpression | determines if the string returned is the name of a field or an expression |
isValid | determines if the expression (or field) returned is valid |
Definition at line 140 of file qgsfieldexpressionwidget.cpp.
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protectedslot |
Definition at line 353 of file qgsfieldexpressionwidget.cpp.
QString QgsFieldExpressionWidget::currentText | ( | ) | const |
Returns the current text that is set in the expression area.
Definition at line 114 of file qgsfieldexpressionwidget.cpp.
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protectedslot |
open the expression dialog to edit the current or add a new expression
Definition at line 239 of file qgsfieldexpressionwidget.cpp.
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overrideprotected |
Definition at line 310 of file qgsfieldexpressionwidget.cpp.
QString QgsFieldExpressionWidget::expression | ( | ) | const |
Returns the currently selected field or expression.
If a field is currently selected, the returned value will be converted to a valid expression referencing this field (ie enclosing the field name with appropriate quotations).
Alias for asExpression()
Definition at line 124 of file qgsfieldexpressionwidget.cpp.
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inline |
Returns the title used for the expression dialog.
Definition at line 75 of file qgsfieldexpressionwidget.h.
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protectedslot |
when expression is edited by the user in the line edit, it will be checked for validity
Definition at line 269 of file qgsfieldexpressionwidget.cpp.
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protectedslot |
when expression has been edited (finished) it will be added to the model
Definition at line 275 of file qgsfieldexpressionwidget.cpp.
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signal |
Emitted when the currently selected field changes.
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signal |
fieldChanged signal with indication of the validity of the expression
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inline |
currently used filter on list of fields
Definition at line 97 of file qgsfieldexpressionwidget.h.
bool QgsFieldExpressionWidget::isExpression | ( | ) | const |
If the content is not just a simple field this method will return true
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Definition at line 135 of file qgsfieldexpressionwidget.cpp.
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protectedslot |
Definition at line 407 of file qgsfieldexpressionwidget.cpp.
bool QgsFieldExpressionWidget::isValidExpression | ( | QString * | expressionError = nullptr | ) | const |
Returns true
if the current expression is valid.
Definition at line 129 of file qgsfieldexpressionwidget.cpp.
QgsVectorLayer * QgsFieldExpressionWidget::layer | ( | ) | const |
Returns the layer currently associated with the widget.
Definition at line 156 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::registerExpressionContextGenerator | ( | const QgsExpressionContextGenerator * | generator | ) |
Register an expression context generator class that will be used to retrieve an expression context for the widget.
generator | A QgsExpressionContextGenerator class that will be used to create an expression context when required. |
Definition at line 161 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::setAllowEmptyFieldName | ( | bool | allowEmpty | ) |
Sets whether an optional empty field ("not set") option is shown in the combo box.
Definition at line 83 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::setAllowEvalErrors | ( | bool | allowEvalErrors | ) |
Allow accepting expressions with evaluation errors.
This can be useful when we are not able to provide an expression context of which we are sure it's completely populated.
Definition at line 329 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::setButtonVisible | ( | bool | visible | ) |
Set the visibility of the button.
If button is hidden, the widget essentially becomes an editable combo box
Definition at line 344 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::setCustomPreviewGenerator | ( | const QString & | label, |
const QList< QPair< QString, QVariant > > & | choices, | ||
const std::function< QgsExpressionContext(const QVariant &) > & | previewContextGenerator | ||
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Sets the widget to run using a custom preview generator.
In this mode, the widget will call a callback function to generate a new QgsExpressionContext as the previewed object changes. This can be used to provide custom preview values for different objects (i.e. for objects which aren't vector layer features).
label | The label to display for the combo box presenting choices of objects. This should be a representative name, eg "Band" if the widget is showing choices of raster layer bands |
choices | A list of choices to present to the user. Each choice is a pair of a human-readable label and a QVariant representing the object to preview. |
previewContextGenerator | A function which takes a QVariant representing the object to preview, and returns a QgsExpressionContext to use for previewing the object. |
Definition at line 166 of file qgsfieldexpressionwidget.cpp.
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slot |
Sets the current expression text and if applicable also the field.
Alias for setField.
Definition at line 234 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::setExpressionDialogTitle | ( | const QString & | title | ) |
define the title used in the expression dialog
Definition at line 73 of file qgsfieldexpressionwidget.cpp.
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slot |
sets the current field or expression in the widget
Definition at line 191 of file qgsfieldexpressionwidget.cpp.
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slot |
Sets the fields used in the widget to fields, this allows the widget to work without a layer.
Definition at line 229 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::setFilters | ( | QgsFieldProxyModel::Filters | filters | ) |
setFilters allows filtering according to the type of field
Definition at line 78 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::setGeomCalculator | ( | const QgsDistanceArea & | da | ) |
Sets the geometry calculator used in the expression dialog.
Definition at line 109 of file qgsfieldexpressionwidget.cpp.
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slot |
Sets the layer used to display the fields and expression.
Definition at line 173 of file qgsfieldexpressionwidget.cpp.
void QgsFieldExpressionWidget::setLeftHandButtonStyle | ( | bool | isLeft | ) |
Definition at line 94 of file qgsfieldexpressionwidget.cpp.
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inlineslot |
sets the current row in the widget
Definition at line 273 of file qgsfieldexpressionwidget.h.
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protectedslot |
updateLineEditStyle will re-style (color/font) the line edit depending on content and status
expression | if expression is given it will be evaluated for the given string, otherwise it takes current expression from the model |
Definition at line 375 of file qgsfieldexpressionwidget.cpp.
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friend |
Definition at line 338 of file qgsfieldexpressionwidget.h.
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readwrite |
Definition at line 51 of file qgsfieldexpressionwidget.h.
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readwrite |
Definition at line 52 of file qgsfieldexpressionwidget.h.
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readwrite |
Definition at line 53 of file qgsfieldexpressionwidget.h.
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readwrite |
Definition at line 49 of file qgsfieldexpressionwidget.h.
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readwrite |
Definition at line 50 of file qgsfieldexpressionwidget.h.