generalize a c++ method

[jsulm]

@LeLev This small example works for me:

#include <iostream>

class A
{
public:
    typedef void (A::*MethodPtr) ();
    void someMethod() { std::cout << "Hallo!" << std::endl; }
    void uaSub2(MethodPtr updateHandlerPtr){
       (this->* updateHandlerPtr)();
    }
};

int main()
{
    A a;
    a.uaSub2(&A::someMethod); 
    return 0;
}

[ODБOï]

@jsulm yes sorry that is the first one i have tryed:

uaSub2(nIndexNode,"ns=4;s=MAIN.nIndex", &MachineBackend::nIndexUpdated);

// err :  cannot initialize a parameter of type 'Machinebackend::MethorPtr' (aka 'void (MAchinebackend::*)()') with an rvalue of type 'void (MAchineBAckend::*)(QOpcUa::NodeAttribute, const QVariant &)' : different number of parameters (0 vs 2)

error : no matching function for call to 'MachineBackend::uaSub2(QScopedPointer<QOpcUaNode>&, const char [19], <unresolved overloaded function type>)'
         uaSub2(nIndexNode,"ns=4;s=MAIN.nIndex",MachineBackend::nIndexUpdated);
                                                                             ^

[jsulm]

This post is deleted!

[jsulm]

@LeLev said in generalize a c++ method:

nIndexUpdated

This one has parameters, you need to adapt your typedef for the pointer accordingly.
This is what the error tells you.

[ODБOï]

@jsulm

class MachineBackend : public QObject
{
    typedef void (MachineBackend::*MethodPtr) ();
    Q_OBJECT

void nIndexUpdated(QOpcUa::NodeAttribute attr, const QVariant &value){...}

void uaSub2(QScopedPointer<QOpcUaNode>&node, QString nodeId, MethodPtr updateHandlerPtr){
       
       (this->*updateHandlerPtr)();

    }
};

in the constructor of this class i call m_client.connectToServer(), then connect stateChanged signal of the m_client to a method where i want to create the subscriptions :

 QObject::connect(m_client.data(), &QOpcUaClient::stateChanged, this, &MachineBackend::clientStateHandler);

void MachineBackend::clientStateHandler(QOpcUaClient::ClientState state)
{
    setConnected((state == QOpcUaClient::ClientState::Connected)); 

    if (state == QOpcUaClient::ClientState::Connected) {// if client is connected i create subscriptions
                 
        // uaSub(nIndexNode,"ns=4;s=MAIN.nIndex",*nIndexUpdated); // function pointer to static function

        // uaSub1(nIndexNode,"ns=4;s=MAIN.nIndex", MachineBackend::NINDEX) // enum
        
         uaSub2(nIndexNode,"ns=4;s=MAIN.nIndex",&MachineBackend::nIndexUpdated);   

    }

   [...]
}

I think i have to adapt my typedef because &QOpcUaClient::stateChanged returns 2 parameters

[jsulm]

@LeLev said in generalize a c++ method:

I think i have to adapt my typedef

Yes, you have to specify the parameter types when defining a function/method pointer type.

[ODБOï]

i'm having troubles to adapt the typedef..
should it be

typedef void (MachineBackend::*MethodPtr) (QOpcUa::NodeAttribute attr,const QVariant &value);

 or 

typedef void (MachineBackend::*MethodPtr(QOpcUa::NodeAttribute attr,const QVariant &value)) ();

[jsulm]

@LeLev said in generalize a c++ method:

typedef void (MachineBackend::*MethodPtr) (QOpcUa::NodeAttribute attr,const QVariant &value);

typedef void (MachineBackend::*MethodPtr) (QOpcUa::NodeAttribute, const QVariant&);

No need for parameter names, only types.

[ODБOï]

@jsulm

class MachineBackend : public QObject
{
    typedef void (MachineBackend::*MethodPtr) (QOpcUa::NodeAttribute, const QVariant&);

    Q_OBJECT

public:
    void uaSub2(QScopedPointer<QOpcUaNode>&node, QString nodeId, MethodPtr updateHandlerPtr){
 
      //  trying to use lambda to call my pointed function but can't

      /*  QObject::connect(node.data(),&QOpcUaNode::attributeUpdated,[&]{
             (this->*updateHandlerPtr() ) ();
        });
     */ 
  
         // maybe  is it possible to connect to my function directly  ?     
     QObject::connect(node.data(),&QOpcUaNode::attributeUpdated,this,&MachineBackend:: ??)

    }
    

};

[jsulm]

@LeLev said in generalize a c++ method:

(this->*updateHandlerPtr() ) ();

(this->*updateHandlerPtr) (); <--- You have to pass 2 parameters to it!

[ODБOï]

@jsulm yes but i don't have any parameter to pass to it .. .

its just a handler function that must be connected to
QOpcUaNode::attributeUpdated witch returns 2 values ;

that is why it has to have 2 params.

I don't want to call that function, i want it to be connected to

QOpcUaNode::attributeUpdated , and called automatically when attributeUpdated is emitted in the opcua backend

[ODБOï]

@jsulm finally it is this working thanks to you !

class MachineBackend : public QObject
{
    typedef void (MachineBackend::*MethodPtr) (QOpcUa::NodeAttribute, const QVariant&);

    Q_OBJECT


public:


    void uaSub2(QScopedPointer<QOpcUaNode>&node, QString nodeId, MethodPtr updateHandlerPtr){

     QObject::connect(node.data(),&QOpcUaNode::attributeUpdated,this,updateHandlerPtr);

    }

  void nIndexUpdated(QOpcUa::NodeAttribute attr, const QVariant &value){
        //return; // i can access member variables / signal / methods here
    }


// use uaSub

uaSub2(nIndexNode,"ns=4;s=MAIN.nIndex",&MachineBackend::nIndexUpdated);
//

};

thank you infinitely everybody who helped me