Add some Qt database helpers

qt_db_helpers.hpp

@@ -0,0 +1,75 @@
+#ifndef QT_DB_HELPERS_HPP_
+#define QT_DB_HELPERS_HPP_
+
+#include <utility>
+#include <stdexcept>
+#include <QString>
+#include <QSqlError>
+#include <QSqlTableModel>
+
+template<typename T, typename Func, typename... Args>
+void SQL_error_check (T&& object, Func func, Args&&... args)
+{
+  if (!(std::forward<T> (object).*func) (std::forward<Args> (args)...))
+    {
+      auto error = object.lastError ();
+      if (QSqlError::NoError != error.type ())
+        {
+          throw std::runtime_error {("Database Error: " + error.text ()).toStdString ()};
+        }
+    }
+}
+
+class ConditionalTransaction final
+  : private boost::noncopyable
+{
+public:
+  explicit ConditionalTransaction (QSqlTableModel& model)
+    : model_ {model}
+    , submitted_ {false}
+  {
+    model_.database ().transaction ();
+  }
+  bool submit (bool throw_on_error = true)
+  {
+    Q_ASSERT (model_.isDirty ());
+    bool ok {true};
+    if (throw_on_error)
+      {
+        SQL_error_check (model_, &QSqlTableModel::submitAll);
+      }
+    else
+      {
+        ok = model_.submitAll ();
+      }
+    submitted_ = submitted_ || ok;
+    return ok;
+  }
+  void revert ()
+  {
+    Q_ASSERT (model_.isDirty ());
+    model_.revertAll ();
+  }
+  ~ConditionalTransaction ()
+  {
+    if (model_.isDirty ())
+      {
+        // abandon un-submitted changes to the model
+        model_.revertAll ();
+      }
+    auto database = model_.database ();
+    if (submitted_)
+      {
+        SQL_error_check (database, &QSqlDatabase::commit);
+      }
+    else
+      {
+        database.rollback ();
+      }
+  }
+private:
+  QSqlTableModel& model_;
+  bool submitted_;
+};
+
+#endif

wsjtx.pro

@@ -70,7 +70,7 @@ SOURCES += \
   EqualizationToolsDialog.cpp \
   LotWUsers.cpp TraceFile.cpp
 
-HEADERS  += qt_helpers.hpp \
+HEADERS  += qt_helpers.hpp qt_db_helpers.hpp \
   pimpl_h.hpp pimpl_impl.hpp \
   Radio.hpp NetworkServerLookup.hpp revision_utils.hpp \
   soundin.h soundout.h \