Calling a method before executing a slot

fmope

Hello,

I would like to ask whether it is possible to perform a specific function before executing a slot? I mean a mechanism similar to "before triggers" found in SQL.

Example:

class TestA : public QObject
{
     Q_OBJECT

public slots:
     void slotOne();
     void slotTwo();

private:
    bool ready;
    void beforeAnySlot()
    {
         if(ready)
              //execute slot
         else
              //reject
    }
};

I would like to skip this solution:

void slotOne() 
{
    if(!ready)
        return;
}

void slotTwo() 
{
    if(!ready)
        return;
}

Regards
Paul

jsulm

No, there is no such mechanism. But you could connect the signals to the slots when ready becomes true and disconnect when it becomes false.

fmope

Unfortunately I can not use this solution, because I want to use QWebChannel.

mrjj

hi
Could you not call a function from the slots that
can check if ready before performing the "action" ?

If you provide more info about your use case, we might get good ideas :)

fmope

Example code:

class MyClass2 : public QObject
{
    Q_OBJECT

public slots:
    void logout()
    {
        //can call slot only if user is logged
    }

    void slot2()
    {
        //can call slot only if user is logged
    }

    //...

private:
    bool logged;
}

class Client : public QObject
{
   Q_OBJECT

public:   

   Client() 
   {
       channel.registerObject("dashboard", myClass);
       channel.registerObject("user", myClass2);
       //...
   }

   QWebChannel channel;
   QWebSocket socket;
   MyClass myClass;
   MyClass2 myClass2;
}

I want to avoid a situation where the client-side method 'logout' is called when the user is offline.

//client.js

//...
channel.objects.user.logout();

By limiting Web Channel can not register the object 'user' at the moment when the client logs in. Because the objects must be registered before initialize the client.
"Note: A current limitation is that objects must be registered before any client is initialized."

mrjj

Ok. i see.

who will call the slots?

Could the signals go to same slot and you use the
sender() to know whom send
the signal?
That way u need only check once.

jsulm

@fmope You should always check whether the user is logged on or not in logout()! It is similar to the rule: check input parameters before using them and don't expect them to be always correct.