This might be promising...

api/container/connectionlist.h

@@ -24,13 +24,14 @@ namespace iRail
     class ConnectionList : public QAbstractListModel
     {
     Q_OBJECT
-    public:
+    private:
         // Construction and destruction
         ConnectionList(const Journey::Id& iJourney, QObject* iParent = 0);
         ~ConnectionList();
         friend class ContainerCache;
 
         // Basic I/O
+    public:
         const Journey::Id& journeyId() const;
 
         // Model interface

api/data.h

@@ -0,0 +1,64 @@
+//
+// Configuration
+//
+
+// Include guard
+#ifndef DATA_H
+#define DATA_H
+
+// Includes
+#include <QObject>
+#include <QHash>
+
+namespace iRail
+{
+    class Data : public QObject
+    {
+    Q_OBJECT
+    Q_PROPERTY(Id id READ id CONSTANT)
+    public:
+        // Auxiliary types
+        struct Id
+        {
+            // Operator implementation
+            virtual bool equals(const Id& id) const = 0;
+            virtual unsigned int hash() const = 0;
+
+            // Operators
+            friend unsigned int qHash(const Id& id);
+            friend bool operator==(const Id& lhs, const Id& rhs);
+        };
+
+        // Basic I/O
+        virtual Id& id() const = 0;
+
+        // Operator implementation
+        virtual bool equals(const Data& data) const = 0;
+        virtual Data& assign(const Data& data) = 0;
+
+        // Operators
+        virtual Data& operator=(const Data& data)
+        {
+            return assign(data);
+        }
+
+        friend bool operator==(const Data& lhs, const Data& rhs);
+    };
+
+    unsigned int qHash(const Data::Id& id)
+    {
+        return id.hash();
+    }
+
+    bool operator==(const Data::Id& lhs, const Data::Id& rhs)
+    {
+        return lhs.equals(rhs);
+    }
+
+    bool operator==(const Data& lhs, const Data& rhs)
+    {
+        return lhs.equals(rhs);
+    }
+}
+
+#endif // DATA_H

api/data/connection.cpp

@@ -65,19 +65,21 @@ void Connection::setDelay(unsigned int iDelay)
 
 
 //
-// Operators
+// Operator implementation
 //
 
-bool iRail::operator==(const Connection& lhs, const Connection& rhs)
+bool Connection::equals(const Data& data) const
 {
-    return  (lhs.departure() == rhs.departure() &&
-             lhs.arrival() == rhs.arrival() &&
-             lhs.terminus() == rhs.terminus() &&
-             lhs.vehicle() == rhs.vehicle());
+    const Connection& other = dynamic_cast<const Connection&>(data);
+    return  (departure() == other.departure() &&
+             arrival() == other.arrival() &&
+             terminus() == other.terminus() &&
+             vehicle() == other.vehicle());
 }
 
-Connection& Connection::operator=(const Connection& other)
+Data& Connection::assign(const Data& data)
 {
+    const Connection& other = dynamic_cast<const Connection&>(data);
     if (this != &other)
     {
         Q_ASSERT(this->id() == other.id());
@@ -89,13 +91,14 @@ Connection& Connection::operator=(const Connection& other)
     return *this;
 }
 
-inline unsigned int qHash(const Connection::Id& iConnection)
+unsigned int Connection::Id::hash()
 {
-    return (3*qHash(iConnection.origin)) ^ (5*qHash(iConnection.destination));
+    return (3*qHash(origin)) ^ (5*qHash(destination));
 }
 
-bool iRail::operator==(const Connection::Id& lhs, const Connection::Id& rhs)
+bool Connection::Id::equals(const Data::Id& data) const
 {
-    return  (lhs.origin->id() == rhs.origin->id() &&
-             lhs.destination->id() == rhs.destination->id());
+    const Connection::Id& other = dynamic_cast<const Connection::Id&>(data);
+    return  (origin->id() == other.origin->id() &&
+             destination->id() == other.destination->id());
 }

api/data/connection.h

@@ -30,8 +30,10 @@ namespace iRail
         {
             Stop const* origin;
             Stop const* destination;
-            friend inline unsigned int qHash(const Connection::Id& iConnection);
-            friend bool operator==(const Connection::Id& lhs, const Connection::Id& rhs);
+
+            // Operator implementation
+            bool equals(const Data::Id& id) const;
+            unsigned int hash() const;
         };
         enum Roles
         {
@@ -54,20 +56,16 @@ namespace iRail
         unsigned int delay() const;
         void setDelay(unsigned int iDelay);
 
-        // Operators
-        friend bool operator==(const Connection& lhs, const Connection& rhs);
-        Connection& operator=(const Connection& other);
+        // Operator implementation
+        bool equals(const Data& data) const;
+        Data& assign(const Data& data);
 
     private:
         Id mId;
         Station const* mTerminus;
         Vehicle const* mVehicle;
         unsigned int mDelay;
     };
-
-    bool operator==(const Connection& lhs, const Connection& rhs);
-    inline unsigned int qHash(const Connection::Id& iConnection);
-    bool operator==(const Connection::Id& lhs, const Connection::Id& rhs);
 }
 
 Q_DECLARE_METATYPE(iRail::Connection::Id)

api/data/departure.cpp

@@ -43,17 +43,19 @@ void Departure::setDelay(unsigned int iDelay)
 
 
 //
-// Operators
+// Operator implementation
 //
 
-bool iRail::operator==(const Departure& lhs, const Departure& rhs)
+bool Departure::equals(const Data& data)
 {
-    return  (lhs.id().vehicle == rhs.id().vehicle &&
-             lhs.id().origin == rhs.id().origin);
+    const Departure& other = dynamic_cast<const Departure&>(data);
+    return  (id().vehicle == other.id().vehicle &&
+             id().origin == other.id().origin);
 }
 
-Departure& Departure::operator=(const Departure& other)
+Data& Departure::assign(const Data& data)
 {
+    const Departure& other = dynamic_cast<const Departure&>(data);
     if (this != &other)
     {
         Q_ASSERT(this->id() == other.id());
@@ -63,13 +65,14 @@ Departure& Departure::operator=(const Departure& other)
     return *this;
 }
 
-inline unsigned int qHash(const Departure::Id& iDepartureId)
+unsigned int Departure::Id::hash()
 {
-    return qHash(iDepartureId.origin) ^ qHash(iDepartureId.vehicle);
+    return qHash(origin) ^ qHash(vehicle);
 }
 
-bool iRail::operator==(const Departure::Id& lhs, const Departure::Id& rhs)
+bool Departure::Id::equals(const Data::Id& data) const
 {
-    return  (lhs.vehicle->id() == rhs.vehicle->id() &&
-             lhs.origin->id() == rhs.origin->id());
+    const Departure::Id& other = dynamic_cast<const Departure::Id&>(data);
+    return  (vehicle->id() == other.vehicle->id() &&
+             origin->id() == other.origin->id());
 }

api/data/departure.h

@@ -28,8 +28,10 @@ namespace iRail
         {
             Stop const* origin;
             Vehicle const* vehicle;
-            friend inline unsigned int qHash(const Departure::Id& iDepartureId);
-            friend bool operator==(const Departure::Id& lhs, const Departure::Id& rhs);
+
+            // Operator implementation
+            bool equals(const Data::Id& id) const;
+            unsigned int hash() const;
         };
         enum Roles
         {
@@ -46,18 +48,14 @@ namespace iRail
         unsigned int delay() const;
         void setDelay(unsigned int iDelay);
 
-        // Operators
-        friend bool operator==(const Departure& lhs, const Departure& rhs);
-        Departure& operator=(const Departure& other);
+        // Operator implementation
+        bool equals(const Data& data) const;
+        Data& assign(const Data& data);
 
     private:
         Id mId;
         unsigned int mDelay;
     };
-
-    bool operator==(const Departure& lhs, const Departure& rhs);
-    inline unsigned int qHash(const Departure::Id& iDepartureId);
-    bool operator==(const Departure::Id& lhs, const Departure::Id& rhs);
 }
 
 Q_DECLARE_METATYPE(iRail::Departure::Id)

api/data/journey.cpp

@@ -43,17 +43,19 @@ void Journey::setDelay(unsigned int iDelay)
 
 
 //
-// Operators
+// Operator implementation
 //
 
-bool iRail::operator==(const Journey& lhs, const Journey& rhs)
+bool Journey::equals(const Data& data)
 {
-    return  (lhs.id().origin || rhs.id().origin &&
-             lhs.id().destination || rhs.id().destination);
+    const Journey& other = dynamic_cast<const Journey&>(data);
+    return  (id().origin || other.id().origin &&
+             id().destination || other.id().destination);
 }
 
-Journey& Journey::operator=(const Journey& other)
+Data& Journey::assign(const Data& data)
 {
+    const Journey& other = dynamic_cast<const Journey&>(data);
     if (this != &other)
     {
         Q_ASSERT(this->id() == other.id());
@@ -63,13 +65,14 @@ Journey& Journey::operator=(const Journey& other)
     return *this;
 }
 
-unsigned int qHash(const Journey::Id& iJourneyId)
+unsigned int Journey::Id::hash()
 {
-    return (3*qHash(iJourneyId.origin)) ^ (5*qHash(iJourneyId.destination));
+    return (3*qHash(origin)) ^ (5*qHash(destination));
 }
 
-bool iRail::operator==(const Journey::Id& lhs, const Journey::Id& rhs)
+bool Journey::Id::equals(const Data::Id& data) const
 {
-    return  (lhs.origin->id() == rhs.origin->id() &&
-             lhs.destination->id() == rhs.destination->id());
+    const Journey::Id& other = dynamic_cast<const Journey::Id&>(data);
+    return  (origin->id() == other.origin->id() &&
+             destination->id() == other.destination->id());
 }

api/data/journey.h

@@ -28,8 +28,10 @@ namespace iRail
         {
             Stop const* origin;
             Stop const* destination;
-            friend inline unsigned int qHash(const Journey::Id& iJourneyId);
-            friend bool operator==(const Journey::Id& lhs, const Journey::Id& rhs);
+
+            // Operator implementation
+            bool equals(const Data::Id& id) const;
+            unsigned int hash() const;
         };
 
         enum Roles
@@ -47,18 +49,14 @@ namespace iRail
         unsigned int delay() const;
         void setDelay(unsigned int iDelay);
 
-        // Operators
-        friend bool operator==(const Journey& lhs, const Journey& rhs);
-        Journey& operator=(const Journey& other);
+        // Operator implementation
+        bool equals(const Data& data) const;
+        Data& assign(const Data& data);
 
     private:
         Id mId;
         unsigned int mDelay;
     };
-
-    bool operator==(const Journey& lhs, const Journey& rhs);
-    inline unsigned int qHash(const Journey::Id& iJourneyId);
-    bool operator==(const Journey::Id& lhs, const Journey::Id& rhs);
 }
 
 Q_DECLARE_METATYPE(iRail::Journey::Id)

api/data/station.cpp

@@ -58,18 +58,20 @@ void Station::setLocation(const Location& iLocation)
 
 
 //
-// Operators
+// Operator implementation
 //
 
-bool iRail::operator==(const Station& lhs, const Station& rhs)
+bool Station::equals(const Data& data) const
 {
-    return  (lhs.id() == rhs.id() &&
-             lhs.name() == rhs.name() &&
-             *(lhs.location()) == *(rhs.location()));
+    const Station& other = dynamic_cast<const Station&>(data);
+    return  (id() == other.id() &&
+             name() == other.name() &&
+             *(location()) == *(other.location()));
 }
 
-Station& Station::operator=(const Station& other)
+Data& Station::assign(const Data& data)
 {
+    const Station& other = dynamic_cast<const Station&>(data);
     if (this != &other)
     {
         Q_ASSERT(this->id() == other.id());
@@ -80,6 +82,17 @@ Station& Station::operator=(const Station& other)
     return *this;
 }
 
+unsigned int Station::Id::hash()
+{
+    return qHash(guid);
+}
+
+bool Station::Id::equals(const Data::Id& data) const
+{
+    const Station::Id& other = dynamic_cast<const Station::Id&>(data);
+    return  (guid == other.guid);
+}
+
 QDataStream& iRail::operator<<(QDataStream& iStream, const Station& iStation)
 {
     iStream << iStation.mId;
@@ -98,7 +111,3 @@ QDataStream& iRail::operator>>(QDataStream& iStream, Station& iStation)
     return iStream;
 }
 
-inline unsigned int iRail::qHash(const Station &iStation)
-{
-    return qHash(iStation.id());
-}