As dynamic libraries to use class variables?

[Mikee]

It is my *.pro file. What to do next?

QT       -= gui

TARGET = StrategyCod
TEMPLATE = lib

DEFINES += STRATEGYCOD_LIBRARY
DEFINES += QT_DEPRECATED_WARNINGS

SOURCES += \
        strategycod.cpp

HEADERS += \
        strategycod.h \
        strategycod_global.h 

unix {
    target.path = /usr/lib
    INSTALLS += target
}

INCLUDEPATH = c : / mainwindow.h/include

[mrjj]

@Mikee said in As dynamic libraries to use class variables?:

INCLUDEPATH = c : / mainwindow.h/include

That is complete wrong syntax ?

INCLUDEPATH = "C:/Qt/project/MyCandleSrick"

if that is the folder where it should look for the other files.

[Mikee]

I replaced. What to do next?

QT       -= gui

TARGET = StrategyCod
TEMPLATE = lib

DEFINES += STRATEGYCOD_LIBRARY
DEFINES += QT_DEPRECATED_WARNINGS
SOURCES += \
        strategycod.cpp

HEADERS += \
        strategycod.h \
        strategycod_global.h 

unix {
    target.path = /usr/lib
    INSTALLS += target
}

#INCLUDEPATH = C: / Qt / project / MyCandleSrick/include
INCLUDEPATH = "C: / Qt / project / MyCandleSrick"

[mrjj]

@Mikee said in As dynamic libraries to use class variables?:

INCLUDEPATH = "C: / Qt / project / MyCandleSrick"

Why the spaces ?
Seems not correct.

-What to do next?
Depends on what you are trying ?
If you can now build your library and get a DLL
then you should load that library in your main app and
try to call function StrategyCod2 with your data.

https://wiki.qt.io/How_to_create_a_library_with_Qt_and_use_it_in_an_application
See section "Loading the library using QLibrary"

Since you are not exporting void StrategyCod2()
you need to resolve it to call it.
http://doc.qt.io/qt-5/qlibrary.html#resolve

[Mikee]

This is my library:
StrategyCod.pro:

QT       -= gui

TARGET = StrategyCod
TEMPLATE = lib

DEFINES += STRATEGYCOD_LIBRARY

# The following define makes your compiler emit warnings if you use
# any feature of Qt which has been marked as deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if you use deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
        strategycod.cpp

HEADERS += \
        strategycod.h \
        strategycod_global.h 

unix {
    target.path = /usr/lib
    INSTALLS += target
}

#INCLUDEPATH = C: / Qt / project / MyCandleSrick/include
INCLUDEPATH = "C:/Qt/project/MyCandleSrick"

strategycod.h:

#ifndef STRATEGYCOD_H
#define STRATEGYCOD_H

#include "strategycod_global.h"


extern "C" {STRATEGYCODSHARED_EXPORT void StrategyCod();}

class STRATEGYCODSHARED_EXPORT StrategyCod
{

//public:
   // StrategyCod1();
};

#endif // STRATEGYCOD_H

strategycod_global.h:

#ifndef STRATEGYCOD_GLOBAL_H
#define STRATEGYCOD_GLOBAL_H

#include <QtCore/qglobal.h>

#if defined(STRATEGYCOD_LIBRARY)
#  define STRATEGYCODSHARED_EXPORT Q_DECL_EXPORT
#else
#  define STRATEGYCODSHARED_EXPORT Q_DECL_IMPORT
#endif

#endif // STRATEGYCOD_GLOBAL_H

strategycod.cpp:

#include "strategycod.h"
#include <QDebug>
//#include "C:\\Qt\project\\MyCandleSrick\\mainwindow.h"
//#include <mainwindow>
//StrategyCod::StrategyCod1(){qDebug()<<"Library work1";}



void StrategyCod()
{
    //MainWindow w;
    qDebug()<<"Library work2";//<<w.NBar;
}

This is my app
main.cpp

#include "mainwindow.h"
#include <QApplication>
#include <cstdlib>
#include <QMessageBox>
#include <QtConcurrent/QtConcurrent>
#include <QMutex>
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;    
    QLibrary MyLib("C:\\Qt\\project\\build-StrategyCod-Desktop_Qt_5_9_2_MinGW_32bit-Debug\\debug\\StrategyCod"); 
    MyLib.load();
    typedef void (*MyPrototype)();
    MyPrototype StrategyCod = (MyPrototype) MyLib.resolve("StrategyCod");
    StrategyCod();  
    MyLib.unload();
    w.show();
    return a.exec();
}

In the MainWindow class is written needed variables.
But I can not create an object of MainWindow class in the library and can't use its variables.

[mrjj]

Hi
Ok, and you can call the void StrategyCod() function ? ( that works ?)
If yes, you can now
make it into

void StrategyCod(MainWinow *main) ( it should know the type since u include its .h file)
extern "C" {STRATEGYCODSHARED_EXPORT void StrategyCod(MainWinow *main);}

and from main call it with
typedef void (*MyPrototype)((MainWinow *);
MyPrototype StrategyCod = (MyPrototype) MyLib.resolve("StrategyCod");
StrategyCod(&w); // give it the real MainWindow

There is no reason to try to create a new MainWindow inside the StrategyCod() function as
that would be ANOTHER mainwindow than the running one and not have the right data.

You should give it as parameter.

Using mainwindow seems silly, a Data class would make more sense but can work.
But you should NOT call any functions inside mainwindow from library as there is no event loop running and
it will not work. But you should be able to use public member variables.

[Mikee]

I can call the void StrategyCod() .
I did:
strategycod.h:

#ifndef STRATEGYCOD_H
#define STRATEGYCOD_H

#include "strategycod_global.h"


extern "C" {STRATEGYCODSHARED_EXPORT void StrategyCod(MainWinow * main);}

class STRATEGYCODSHARED_EXPORT StrategyCod
{

//public:
   // StrategyCod1();
};

#endif // STRATEGYCOD_H

strategycod.cpp:

#include "strategycod.h"
#include <QDebug>
//#include "C:\\Qt\project\\MyCandleSrick\\mainwindow.h"
//#include <mainwindow>
//StrategyCod::StrategyCod1(){qDebug()<<"Library work1";}



void StrategyCod(MainWinow * main)
{
    //MainWindow w;
    qDebug()<<"Library work2";//<<w.NBar;
}

6 errors:
C:\Qt\project\StrategyCod\strategycod.h:7: error: variable or field 'StrategyCod' declared void
extern "C" {STRATEGYCODSHARED_EXPORT void StrategyCod(MainWinow * main);}
^
C:\Qt\project\StrategyCod\strategycod.h:7: error: 'MainWinow' was not declared in this scope
C:\Qt\project\StrategyCod\strategycod.h:7: error: 'main' was not declared in this scope
extern "C" {STRATEGYCODSHARED_EXPORT void StrategyCod(MainWinow * main);}
^
C:\Qt\project\StrategyCod\strategycod.cpp:9: оerror: variable or field 'StrategyCod' declared void
void StrategyCod(MainWinow * main)
^
C:\Qt\project\StrategyCod\strategycod.cpp:9: error: 'MainWinow' was not declared in this scope
C:\Qt\project\StrategyCod\strategycod.cpp:9: error: 'main' was not declared in this scope
void StrategyCod(MainWinow * main)
^

[mrjj]

Hi
You must include mainwindw.h so it knows type

trategycod.cpp:
#include "mainwindow.h" // should know where to find it due to the INCLUDEPATH in .pro file

[Mikee]

When i do this same error appers:
C:\Qt\project\MyCandleSrick\mainwindow.h:4: error: QMainWindow: No such file or directory

In the file C:/Qt/project/MyCandleSrick/mainwindow.h:
4:#include <QMainWindow>

[mrjj]

@Mikee
Well you library is with

QT -= gui

so it dont know QMainwindow type ( or any Qt widget type)

[Mikee]

I fixed strategycod.pro:

QT       += core gui

TARGET = StrategyCod
TEMPLATE = lib

DEFINES += STRATEGYCOD_LIBRARY
DEFINES += QT_DEPRECATED_WARNINGS
SOURCES += \
        strategycod.cpp

HEADERS += \
        strategycod.h \
        strategycod_global.h 

unix {
    target.path = /usr/lib
    INSTALLS += target
}
INCLUDEPATH = "C:/Qt/project/MyCandleSrick"

But the error is the same.

[Mikee]

I done this in strategycod.pro

INCLUDEPATH = "C:/Qt/project/MyCandleSrick"  "C:/Qt/Qt5.9.2/5.9.2/Src/qtbase/include/QtWidgets"

Now it included <QMainWindow>. But it isnt working now

extern "C" {STRATEGYCODSHARED_EXPORT void StrategyCod(MainWinow * main);}

and

void StrategyCod(MainWinow * main)

errors:
C:\Qt\project\StrategyCod\strategycod.h:7: error: variable or field 'StrategyCod' declared void
extern "C" {STRATEGYCODSHARED_EXPORT void StrategyCod(MainWinow * main);}
^
C:\Qt\project\StrategyCod\strategycod.h:7: error: 'MainWinow' was not declared in this scope
C:\Qt\project\StrategyCod\strategycod.h:7: error: 'main' was not declared in this scope
extern "C" {STRATEGYCODSHARED_EXPORT void StrategyCod(MainWinow * main);}
^
C:\Qt\project\StrategyCod\strategycod.cpp:9: оerror: variable or field 'StrategyCod' declared void
void StrategyCod(MainWinow * main)
^
C:\Qt\project\StrategyCod\strategycod.cpp:9: error: 'MainWinow' was not declared in this scope
C:\Qt\project\StrategyCod\strategycod.cpp:9: error: 'main' was not declared in this scope
void StrategyCod(MainWinow * main)

[SGaist]

Because when you do INCLUDEPATH = you replace the content of that variable with what follows. Use INCLUDEPATH += to append your folders to it.

[Mikee]

Now all includes are working.
When I use function

void StrategyCod(MainWindow * main)
{
    //MainWindow w;
    main->NBar;
    qDebug()<<"Library work2"<<main->NBar;//<<w.NBar;
}

qDebug message is not a valid value NBar

[Mikee]

I think that need to do reference class variable. But this code isn't working

void StrategyCod(/*MainWindow * main*/)
{
    long long &NBar1 =MainWindow.NBar;
    qDebug()<<"Library work2";//<<w.NBar;
}

How can i do reference?

[mrjj]

@Mikee

via the parameter ( main or what u called it)

void StrategyCod(MainWindow * main) {
    qDebug()<<"Library work2"<<main->NBar;
}

if NBAr is wrong, then something else is wrong. not the function
it might be you call StrategyCod BEFORE setting it in mainwindow or
something like that.

[Mikee]

I checked:
library:
void StrategyCod(double Parametr)

{
    MainWindow *w;
    qDebug()<<"Library work2"<<Parametr<<w->NBar;
}

main.cpp:

QLibrary MyLib("C:\\Qt\\project\\build-StrategyCod-Desktop_Qt_5_9_2_MinGW_32bit-Debug\\debug\\StrategyCod");  
    MyLib.load();
    typedef void (*MyPrototype)();
    MyPrototype StrategyCod = (MyPrototype) MyLib.resolve("StrategyCod");
    qDebug()<<w.NBar;  //NBar=0 is hear 
    StrategyCod();  //NBar=5943858560 is hear 
    MyLib.unload();

Maybe here typedef void (*MyPrototype)(); need append void (*MyPrototype)(class); ?

[mrjj]

@Mikee
Yes it must all match.

typedef void (*MyPrototype)();

means pointer to function takes no parameters
which is untrue.

[Mikee]

But what to do with NBar?

void StrategyCod()
{
    MainWindow *w;
    qDebug()<<"Library work2"<<w->NBar;
  
}

[jsulm]

@Mikee

typedef void (*MyPrototype)(MainWindow *w);