Rework of catalog objects. Several of them are now inheriting from common

base classes that implement common functionality.

pglab/CrudTab.h

@@ -5,6 +5,7 @@
 #include <QWidget>
 #include "PlgPage.h"
 #include <memory>
+#include <optional>
 
 namespace Ui {
 	class CrudTab;
@@ -20,7 +21,7 @@ class CrudTab : public PlgPage
 
 public:
 	explicit CrudTab(MainWindow *parent = 0);
-	~CrudTab();
+	~CrudTab() override;
 
 	void setConfig(std::shared_ptr<OpenDatabase> db, const PgClass &table);
 
@@ -33,7 +34,7 @@ private:
 	MainWindow *m_window;
 
 	std::shared_ptr<OpenDatabase> m_db;
-	PgClass m_table;
+	std::optional<PgClass> m_table;
 
 	CrudModel *m_crudModel = nullptr;
 	std::vector<QAction*> actions;