The ASyncDBConnection class uses C++ std::function callbacks now for reporting notices and state changes.

While I like some aspects of Qt's signals and slots system I prefer to
rely on more standard C++.

pglab/ASyncDBConnection.cpp

@@ -4,19 +4,19 @@
 
 using namespace boost::asio;
 
-namespace {
+//namespace {
 
-    class registerMetaTypes {
+//    class registerMetaTypes {
-    public:
+//    public:
-        registerMetaTypes()
+//        registerMetaTypes()
-        {
+//        {
-            qRegisterMetaType<ASyncDBConnection::State>();
+//            qRegisterMetaType<ASyncDBConnection::State>();
-            qRegisterMetaType<Pgsql::ErrorDetails>();
+//            qRegisterMetaType<Pgsql::ErrorDetails>();
-        }
+//        }
-    } registerMetaTypes_instance;
+//    } registerMetaTypes_instance;
     
     
-}
+//}
 
 ASyncDBConnection::ASyncDBConnection(boost::asio::io_service &ios)
     : m_asioSock(ios)
@@ -87,7 +87,8 @@ void ASyncDBConnection::doStateCallback(State state)
         m_connection.setNoticeReceiver(
             [this](const PGresult *result) { processNotice(result); });
     }
-	emit onStateChanged(state);	
+	if (m_stateChangeReceiver)
+		m_stateChangeReceiver(state);
 }
 
 
@@ -136,7 +137,7 @@ void ASyncDBConnection::async_query_handler(boost::system::error_code ec, std::s
             while ( ! finished && ! m_connection.isBusy()) {
                 auto res = m_connection.getResult();
                 qint64 ms = m_timer.restart();
-                on_result(res, ms);
+				on_result(res, ms); // do we really want to send null result to???
                 if (res == nullptr) {
                     m_timer.invalidate();
                     doStateCallback(State::Connected);
@@ -169,5 +170,16 @@ bool ASyncDBConnection::cancel()
 void ASyncDBConnection::processNotice(const PGresult *result)
 {
     Pgsql::ErrorDetails details = Pgsql::ErrorDetails::createErrorDetailsFromPGresult(result);
-	emit onNotice(details);
+	if (m_noticeReceiver)
+		m_noticeReceiver(details);
+}
+
+void ASyncDBConnection::setStateChangeReceiver(StateChangeReceiver state_change_receiver)
+{
+	m_stateChangeReceiver = state_change_receiver;
+}
+
+void ASyncDBConnection::setNoticeReceiver(NoticeReceiver notice_receiver)
+{
+	m_noticeReceiver = notice_receiver;
 }

pglab/ASyncDBConnection.h

@@ -1,14 +1,13 @@
 #ifndef ASYNCDBCONNECTION_H
 #define ASYNCDBCONNECTION_H
 
-#include <QObject>
-
 #include "Pgsql_Connection.h"
 #include "Pgsql_Params.h"
 #include "Pgsql_Result.h"
 #include "Expected.h"
 #include "ConnectionConfig.h"
 #include <QElapsedTimer>
+#include <functional>
 #include <mutex>
 #include <boost/asio/ip/tcp.hpp>
 #include <boost/asio/io_service.hpp>
@@ -16,10 +15,12 @@
 /** \brief Class that handles asynchronous execution of queries.
  *
  * Queries are passed to this class with a routine to call on completion
- * when the result is on that routine is called.
+ * when the result is received that routine is called. The asynchronous
+ * processing is done using boost::asio.
+ *
+ * You can cancel a running query but even then you have to wait for the result.
  */
-class ASyncDBConnection: public QObject {
+class ASyncDBConnection {
-    Q_OBJECT
 public:
 	enum class State {
 		NotConnected,
@@ -39,20 +40,36 @@ public:
 	void setupConnection(const ConnectionConfig &config);
 	void closeConnection();
 
-	/** Sends command to the server.
+	/** \defgroup send These function send queries to the server.
+	 *
+	 * The query string can actually contain multiple queries.
+	 * These functions report their results through a callback function.
+	 * If the command gives multiple results on_result will be called for each result.
+	 *
+	 * \note when the io_service that was passed to the constructor is running
+	 * on a different thread the callback also will be done on that thread. Forward
+	 * the call to your own thread if needed.
+	 *
+	 * \note while you can pass multiple queries to a single send call it is not allowed to
+	 *   send new queries while not all results have been received.
+	 */
 
-	When the result is in on_result will be	called directly within the thread.
+	/** \ingroup send
-
+	 * \brief Function to send a command without parameters to the server.
-	If the command gives multiple results on_result will be called for each result.
+	 */
-	*/
 	bool send(const std::string &command, on_result_callback on_result);
+	/** \ingroup send
+	 * \brief Function to send a a command with parameters to the server.
+	 */
 	bool send(const std::string &command, Pgsql::Params params, on_result_callback on_result);
 
 	bool cancel();
     
-signals:
+	using StateChangeReceiver = std::function<void(ASyncDBConnection::State)>;
-    void onStateChanged(ASyncDBConnection::State state);
+	void setStateChangeReceiver(StateChangeReceiver state_change_receiver);
-    void onNotice(Pgsql::ErrorDetails notice);
+
+	using NoticeReceiver = std::function<void(Pgsql::ErrorDetails)>;
+	void setNoticeReceiver(NoticeReceiver notice_receiver);
 
 private:
 	Pgsql::Connection m_connection;
@@ -60,6 +77,8 @@ private:
 	ConnectionConfig m_config;
 	State m_state = State::NotConnected;
     Pgsql::Canceller m_canceller;
+	StateChangeReceiver m_stateChangeReceiver;
+	NoticeReceiver m_noticeReceiver;
 
     QElapsedTimer m_timer;
     
@@ -69,8 +88,4 @@ private:
     void processNotice(const PGresult *result);
 };
 
-Q_DECLARE_METATYPE(ASyncDBConnection::State);
-Q_DECLARE_METATYPE(Pgsql::ErrorDetails);
-
-
 #endif // ASYNCDBCONNECTION_H

pglab/DatabaseWindow.cpp

@@ -11,8 +11,10 @@ DatabaseWindow::DatabaseWindow(QWidget *parent) :
 {
 	ui->setupUi(this);
 
-    connect(&m_dbConnection, &ASyncDBConnection::onStateChanged, this, &DatabaseWindow::connectionStateChanged);
+	m_dbConnection.setStateChangeReceiver(
-    connect(&m_dbConnection, &ASyncDBConnection::onNotice, this, &DatabaseWindow::receiveNotice);
+				[this](auto s) { QueueTask([this, s]() { connectionStateChanged(s); }); });
+	m_dbConnection.setNoticeReceiver(
+				[this](auto n) { QueueTask([this, n]() { receiveNotice(n); }); });
 }
 
 DatabaseWindow::~DatabaseWindow()

pglab/QueryTab.cpp

@@ -31,8 +31,10 @@ QueryTab::QueryTab(MainWindow *win, QWidget *parent) :
 {
 	ui->setupUi(this);
 
-    connect(&m_dbConnection, &ASyncDBConnection::onStateChanged, this, &QueryTab::connectionStateChanged);
+	m_dbConnection.setStateChangeReceiver(
-    connect(&m_dbConnection, &ASyncDBConnection::onNotice, this, &QueryTab::receiveNotice);
+				[this, win](auto s) { win->QueueTask([this, s]() { connectionStateChanged(s); }); });
+	m_dbConnection.setNoticeReceiver(
+				[this, win](auto n) { win->QueueTask([this, n]() { receiveNotice(n); }); });
 
 	QFont font;
 	font.setFamily("Source Code Pro");