- Qt 5.15
- Qt Remote Objects
- Example 2: Direct Connection with a Dynamic Replica
- Qt 5.15.19 Reference Documentation

# Example 2: Direct Connection with a Dynamic Replica

There are no changes to be made on the source side, as a dynamic Replica only impacts how the requestor node acquires the replica. So, we use the source-side code shown in Example 1.

1. Add replica generation to the project.

   Because the replica is dynamically acquired, no `.rep` file is required unlike in Example 1.

2. Create the remote node and connect it to the source host node.

   The code for this step is unchanged from Example 1.

        QRemoteObjectNode repNode; // create remote object node
        repNode.connectToNode(QUrl(QStringLiteral("local:switch"))); // connect with remote host node

3. Acquire a replica of the remote source object.

   In `main.cpp`, we use a QSharedPointer to hold a replica of the remote object, and then instantiate a replica requestor object:

        #include <QCoreApplication>

        #include "dynamicclient.h"

        int main(int argc, char *argv[])
        {
            QCoreApplication a(argc, argv);

            QSharedPointer<QRemoteObjectDynamicReplica> ptr; // shared pointer to hold replica

            QRemoteObjectNode repNode;
            repNode.connectToNode(QUrl(QStringLiteral("local:switch")));

            ptr.reset(repNode.acquireDynamic("SimpleSwitch")); // acquire replica of source from host node

            DynamicClient rswitch(ptr); // create client switch object and pass replica reference to it
        }

The complete declaration and definition of the requestor class, `DynamicClient`, is as follows:

`dynamicclient.h`

     #ifndef _DYNAMICCLIENT_H
     #define _DYNAMICCLIENT_H

     #include <QObject>
     #include <QSharedPointer>

     #include <QRemoteObjectNode>
     #include <qremoteobjectdynamicreplica.h>

     class DynamicClient : public QObject
     {
         Q_OBJECT
     public:
         DynamicClient(QSharedPointer<QRemoteObjectDynamicReplica> ptr);
         ~DynamicClient();

     Q_SIGNALS:
         void echoSwitchState(bool switchState);// this signal is connected with server_slot(..) slot of source object and echoes back switch state received from source

     public Q_SLOTS:
         void recSwitchState_slot(); // Slot to receive source state
         void initConnection_slot(); //Slot to connect signals/slot on replica initialization

     private:
         bool clientSwitchState; // holds received server switch state
         QSharedPointer<QRemoteObjectDynamicReplica> reptr;// holds reference to replica
      };

     #endif

`dynamicclient.cpp`

     #include "dynamicclient.h"

     // constructor
     DynamicClient::DynamicClient(QSharedPointer<QRemoteObjectDynamicReplica> ptr) :
         QObject(nullptr), reptr(ptr)
     {

         //connect signal for replica valid changed with signal slot initialization
         QObject::connect(reptr.data(), &QRemoteObjectDynamicReplica::initialized, this,
                          &DynamicClient::initConnection_slot);
     }

     //destructor
     DynamicClient::~DynamicClient()
     {
     }

     // Function to initialize connections between slots and signals
     void DynamicClient::initConnection_slot()
     {

         // connect source replica signal currStateChanged() with client's recSwitchState() slot to receive source's current state
        QObject::connect(reptr.data(), SIGNAL(currStateChanged()), this, SLOT(recSwitchState_slot()));
        // connect client's echoSwitchState(..) signal with replica's server_slot(..) to echo back received state
        QObject::connect(this, SIGNAL(echoSwitchState(bool)),reptr.data(), SLOT(server_slot(bool)));
     }

     void DynamicClient::recSwitchState_slot()
     {
        clientSwitchState = reptr->property("currState").toBool(); // use replica property to get currState from source
        qDebug() << "Received source state " << clientSwitchState;
        Q_EMIT echoSwitchState(clientSwitchState); // Emit signal to echo received state back to server
     }

When run together with the source-side example, the output is identical to Example 1.