how to emit signal in a static function ?

[cxl2253]

i defined a signal and want to emit it in a static function. as you know ,the refrenced signal should be static, but signal function cannot be static in qt, how should i do ? how to convert this signal function to static ? Anybody can tell me how to use static_cast to solve the problem?

[aamer4yu]

try implementing a function , say emitMySignal(), from where you emit the signal.
From the static function call this funtion, emitMySignal(), which emits the signal ...

Hope this works

[cxl2253]

My code just like that:
1 class mythreadublic QThread
2 {
3 static void mycallbackfunc();
4 void myfunc()
5 private singlas:
6 void mysignal();
7 }
8 void mythread::myfunc()
9 {
10 somefuntion(mycallbackfunc)
11 }
12 void mythread::mycallbackfunc()
13 {
14 emit mysignal();
15 }

what should i do ? thanks

[aamer4yu]

just trying to understand wat u want to do...

why do u want to emit signal from a static function ?? what purpose do u want to achieve ??

[cxl2253]

because i use third party function, it used the callback .now I want to emit the signal in the callback funtion to inform the qt as indiating the progess. How to solve the problem?can you help me ?

[aamer4yu]

so why do u have to make the callback function as static ??

can u show some code ??

[wysota]

What sense would it make to emit a signal without having an object?

[sunil.thaha]

so why do u have to make the callback function as static ??

Callbacks functions has to be static member functions
Read this to know why http://www.newty.de/fpt/callback.html#intro


Now for the part of emitting a signal from the static function. I believe it makes no sense to have the signal emitted from a static function. Since a static function is not bound to an oobject how will you ever connect to that signal.

you just cannot write

connect( MyClass, SIGNAL( sinalEmittedFromStaticFunction() ), someObject, SLOT( whatEver() );

connect( MyClass, SIGNAL( sinalEmittedFromStaticFunction() ), someObject, SLOT( whatEver() );

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More over if you go through the Qt docs, you will find that the signals cannot be static.

But you can always post/send Custom Events from the static function.

[high_flyer]

I fail to see the need for a call back in a Qt application.
In Qt you can use a signal/slot connection or events.
I am sure that if you explain to us what it is you want to do we can show you how to do this with siganl and slots.

[cxl2253]

yes,you are all right. now I found a solution way. USED a static variable to record this address,then call non-static member function of the class.JUST LIKE THAT.
//mythread.h
1 static unsigned long classAddress;
2 class myclass: public QThread
3 {
Q_Object
4 private:
5 static void myfuntion(); // callback function
6 protected:
7 void run();
8 static void emitMsg( unsigned long user_value,char * filename)
9 {
10 myclass* pthis = (myclass*)user_value; // get this address
11 pthis->emit storescpProgressInfo(filename) ;
12 }
13 signals:
14 void storescpProgressInfo(char * filename);
15 }

//mythread.cpp
16 void myclass::myfuntion(char * filename)
17 {
18 classAddress =(unsigned long)this ;
19 emitMsg(classAddress,filename);
20 }

//main.cpp
21 frmmainWindow::frmmainWindow()
22 {
23 myclass my;
24 connect(&my,SIGNAL(storescpProgressInfo(char *)),this,SLOT(myslot(char *)));
25 }

the myclass can emit the signal,
but frmmainwindow cannot receive the SIGNAL and not load the myslot function, what's wrong ? can you help ?

[sunil.thaha]

Can you explain what exactly you are trying to achieve ? I just could not figure it out.
more over please use the code tags like shown below
[code]
(put your code here)
[/ code]

[high_flyer]

static void emitMsg( unsigned long user_value,char * filename)
 {
 myclass* pthis = (myclass*)user_value; // get this address
 pthis->emit storescpProgressInfo(filename) ;
 }

static void emitMsg( unsigned long user_value,char * filename)
 {
 myclass* pthis = (myclass*)user_value; // get this address
 pthis->emit storescpProgressInfo(filename) ;
 }

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This makes NO SENSE in the context you made it!
Such call back is good, when you have the need to allow some external code to execute code it knows nothing about.
Then, such code will offer a call back signature that it knows, in which you can wrap your code for it to execute.
But in your case you only emit a signal, which means the other code is in the context of your class, which means it must have a pointer to your class, otherwise the signal will have no effect.
If you have pointer to your class, you don't need the call back!

what's wrong ?

What wrong is, that you are not listening to what we are saying to you, and you are not explainig what it is you are trying to do.
We can't help you if you don't supply us with details about your problem.

can you help ?

We try to help, but you need to help us help you.

[cxl2253]

I am sorry.My expression is poor.my problem is that i want to emit signal in the static function which will be used as a param in a callback function. why i must use the callback? because i use a third party libarary ,it used the callback, i have to do it. why i want to emit signal in the static function? I want to let the static function to inform its status and other can response alternatively.
Now the problem is that the emited signal cannot be recieved. tommorrow i will give the detail code, thanks all.