As dynamic libraries to use class variables?

Mikee

Hi.
As dynamic libraries to use class variables?
I have a dynamic library function

void StrategyCod2()
{
    qDebug()<<"Library work2"<<NBar;
}

NBar is a variable of the MainWindow class of the main application.
Please tell me how StrategyCod2 function() use variable NBar?

SGaist

Hi,

Make it a parameter of StrategyCod2

Mikee

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

Make it a parameter of StrategyCod2

But these parameters about 20. Is there another option?

SGaist

Since you are showing only a qDebug statement I would say do it directly in the class that is concerned. Otherwise explain what the methods should really do with these variables.

Mikee

The function of the strategy calculates the functions and variables of the class.
Because I need to pass variables to the function library.

mrjj

@Mikee
use a class struct to hold the variables and
pass that to library function

mydata.h

class mydata {
public:
int x;
QString name;
float NBar;
}

#include "mydata.h"
void StrategyCod2(mydata & data)
{
qDebug()<<"Library work2"<<data.NBar;
}

Mikee

I use class

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include "qcustomplot.h"
#include <QFile>  
#include <QDebug>
#include <QByteArray> 
#include <QString> 
#include <QVector>
#include <QTextStream>
#include <QStringList>
#include <iostream>
#include <QtConcurrent/QtConcurrent>
#include <QMutex>


namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
  long long NBar;

When i do

#include <C:\\Qt\project\\MyCandleSrick\\mainwindow.h>

Appeared error: no files

#include <QMainWindow>
#include "qcustomplot.h"
#include <QFile>  
#include <QDebug> 
#include <QByteArray> 
#include <QString> 
#include <QVector>
#include <QTextStream>
#include <QStringList>
#include <iostream>
#include <QtConcurrent/QtConcurrent>
#include <QMutex>

mrjj

@Mikee
I dont know what "error: no files" is or means or what happens.
where do you do

#include <C:\\Qt\project\\MyCandleSrick\\mainwindow.h> ?
also should be
#include "C:\\Qt\project\\MyCandleSrick\\mainwindow.h"

Mikee

In the library :

#include "C:\\Qt\project\\MyCandleSrick\\mainwindow.h"

error:
C:\Qt\project\MyCandleSrick\mainwindow.h:4: error: QMainWindow: No such file or directory

mrjj

@Mikee
Well what is on line 4 in mainwindow.h ?
It says it cant find what ever you include there.

mrjj

Hi
You should use
http://doc.qt.io/qt-5/qmake-variable-reference.html#includepath

instead of linking to the file with full path

Mikee

4: #include <QMainWindow>
I have no patch, I have a dynamic library.

Mikee

May be need use http://doc.qt.io/Qt-5/qlocalsocket.html ?

mrjj

@Mikee
not a patch, a path
you include with
#include "C:\Qt\project\MyCandleSrick\mainwindow.h"

then in THAT mainwindow.h, if it tries to include something else
it will look in the folder with the .pro file for the current project and
will know nothing about MyCandleSrick folder.

So im saying:
it will not work good for you to include using full paths, it will not be able to find other files.
and hence you should tell it with
http://doc.qt.io/qt-5/qmake-variable-reference.html#includepath
where ALSO to look for other files.
Else it will miss what ever mainwindow.h also includes.

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.