One signal more slots

[paolom]

Hi,
I've a manager who handles more objects, each of them lives in a different thread.
During the creation of this objects, I connect a signal of a manager to a slot of the objects.

My goal is to emit a signal from manager and execute only one object slot.

I think I can enumerate all the objects and then invoke a signal with a parameters than identify the number of the object.
So every object receive the signal but when compare the signal parameter, only one object execute the slot.

I think this is a simple solution, but I don't think it's the best, in particular If I've a large number of objects.

Do you have any solutions?

Thanks

[amleto]

You can just keep a pointer of all objects in the manager and use a QHash using the id parameters to make a key

struct Object
{
  void bar(){/* do nothing */}
};
 
class Manager
{
  QHash<Key, Object*>  map;
 
  void foo()
  {
    // do something with 'key's object:
    Key key;
    map[key]->bar(); // no need to run method for each key/object
  }
};

struct Object
{
  void bar(){/* do nothing */}
};

class Manager
{
  QHash<Key, Object*>  map;

  void foo()
  {
    // do something with 'key's object:
    Key key;
    map[key]->bar(); // no need to run method for each key/object
  }
};

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[paolom]

I can't do this cause the object lives in different threads.

I've something like this:

class Manager : public QObject
{
    Q_OBJECT
 
    signals:
         void invokeObjMethod(int);
 
    private:
        void initManager(){
 
            for ( int idx = 0 ; idx < n; idx++){
                QThread * th = new QThread(this);
                MyObject * obj = new MyObject(idx);
                connect(this,SIGNAL(invokeObjMethod(int)),obj,SLOT(doSomething(int)));
                obj->moveToThread(th);
                th->start();       
           }
       }
}
 
class MyObject : public QObject
{
      Q_OBJECT
      public:
          MyObject(int idx, QObject * parent = 0)
                :QObject(parent),
                m_index(idx){}
 
     private:
          int m_index;
 
     public slots:
          void doSomething(int idx){
                  if ( idx != m_index)
                        return;
 
                  ...do Something ...
           }
}

class Manager : public QObject
{
    Q_OBJECT

    signals:
         void invokeObjMethod(int);

    private:
        void initManager(){

            for ( int idx = 0 ; idx < n; idx++){
                QThread * th = new QThread(this);
                MyObject * obj = new MyObject(idx);
                connect(this,SIGNAL(invokeObjMethod(int)),obj,SLOT(doSomething(int)));
                obj->moveToThread(th);
                th->start();       
           }
       }
}

class MyObject : public QObject
{
      Q_OBJECT
      public:
          MyObject(int idx, QObject * parent = 0)
                :QObject(parent),
                m_index(idx){}

     private:
          int m_index;

     public slots:
          void doSomething(int idx){
                  if ( idx != m_index)
                        return;

                  ...do Something ...
           }
}

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When the manager emit the signal invokeObjMethod(int) all the objects invoke their slot but only one do something.
I want to know if this is the right way or there are other best solu

[spirit]

QSignalMapper?

[paolom]

The QSignalMapper class bundles signals from identifiable senders.
In my case I've only one sender.
I think that is not possible to use QSignalMapper in my case.

Am I wrong?

[yeye_olive]

You are right. QSignalMapper cannot help you here.

There is a simple solution to your problem: QMetaObject::invokeMethod(). No more indices, just do something like

QMetaObject::invokeMethod(pointerToTheMyObjectInstance, "doSomething", Qt::QueuedConnection);

QMetaObject::invokeMethod(pointerToTheMyObjectInstance, "doSomething", Qt::QueuedConnection);

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[paolom]

With this method I can directly call the thread slot of the single object, with QueuedConnection (safety for thread).

I think it's the best solution....many thanks!!!

[amleto]

I can't do this cause the object lives in different threads.

Yes you can, just use invokeMethod and use it with a queued connection slot.