qRegisterMetaType- reference as argument in connect throwing run time error

[prasad_N]

you would have the thread access a destroyed object._

you are referring to below function I think & myData obj; is a class member in my actual code & It never gets destructed before thread finishes. again this is due to writing some code on fly sorry for that.

void myclass::startThread()
{
     myData obj;   //this is class member in actual code & never gets destructed before thread finishes, I just wanted to show the reference variable problem here so I just didn't care this 
 
     emit startMyThread(obj);
}

void myclass::startThread()
{
     myData obj;   //this is class member in actual code & never gets destructed before thread finishes, I just wanted to show the reference variable problem here so I just didn't care this 
 
     emit startMyThread(obj);
}

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Passing a reference is possible, just not via a queued connection._

So what connect should I use, Direct connection making slot to execute in main thread. I think other connections more or less same as these 2 connections except unique connection.

What feature?
To store a reference like a pointer? That you would have to take up with the C++ standard comittee._

passing reference to thread when It is queued connection if there is no other way.

[Lesiok]

myData obj is destroyed immediately after emiting signal. Slot in another thread is run in the future when the object referenced by reference no longer exists.

[prasad_N]

myData obj is destroyed immediately after emiting signal. Slot in another thread is run in the future when the object referenced by reference no longer exists.

That is what I clarified in the above reply, myData obj is actually class member of myclass in my original code. It never gets destroyed before worker thread finishes its work.

[anda_skoa]

you are referring to below function I think & myData obj; is a class member in my actual code & It never gets destructed before thread finishes. again this is due to writing some code on fly sorry for that.

Then you should probably not have used a local variable definition.

So what connect should I use, Direct connection making slot to execute in main thread. I think other connections more or less same as these 2 connections except unique connection.

It depends on your requirements.
If you want the slot to execute in the context of the emitter thread, use a direct connection.
If you want to use the signal/slot bridge as a mean to conveniently copy data between threads, use a queued connection.

passing reference to thread when It is queued connection if there is no other way.

I wouldn't get my hope up. If the C++ Standard committee wanted to allow assigment of reference variables, that would have been possible a long time ago, especially since that has always been possible for pointers.

I.e. if C programmers want to refer to the same object from two different variables (aliasing), they use pointers.
C++ programmers can also use pointers and can use references for the special case where the alias can be initialized with the address of the object, e.g. passing a reference to a constructor, storing it in a reference member.

Cheers,
_

[d_stranz]

Then you should probably not have used a local variable definition.

@prasad_N:
Or at least written it as a commented-out line, with an explanation that "obj" is a class member variable. How are we to understand that when you write it as you did, you weren't posting your actual code? A lot of the discussion here was based on your incorrect posting, and it could have been avoided if you had posted the actual code in the first place.

C++ programmers can also use pointers and can use references for the special case where the alias can be initialized with the address of the object, e.g. passing a reference to a constructor, storing it in a reference member.

And this has the added benefit over storing a pointer member variable in that you are absolutely assured that the member variable is a valid reference to an object instance, whereas anything can be assigned to a pointer member, including nothing.

[prasad_N]

A lot of the discussion here was based on your incorrect posting, and it could have been avoided if you had posted the actual code in the first place.

There was a mistake & people are over emphasizing on that rather than a actual question, Anyhow I will take care from next time while posting.

It depends on your requirements.
If you want the slot to execute in the context of the emitter thread, use a direct connection.
If you want to use the signal/slot bridge as a mean to conveniently copy data between threads, use a queued connection.
_

None of them are not my requirements. As per my requirement & Replay's from you guys I think there is no solution for this at least for now (passing reference across threads if it it is queued connection).

[anda_skoa]

Yes, the only reference that can be stored is a pointer.

Cheers.
_