//! [0] QDesignerPropertyEditorInterface *propertyEditor = 0; propertyEditor = formEditor->propertyEditor(); connect(propertyEditor, SIGNAL(propertyChanged(QString, QVariant)), this, SLOT(checkProperty(QString, QVariant))); //! [0] //! [1] void checkProperty(QString property, QVariant value) { QDesignerPropertyEditorInterface *propertyEditor = 0; propertyEditor = formEditor->propertyEditor(); QObject *object = propertyeditor->object(); MyCustomWidget *widget = qobject_cast<MyCustomWidget>(object); if (widget && property == aProperty && value != expectedValue) {...} } //! [1]