communicate data between two windows

[Albator]

Hello qt people,

I have two mainwindows.ui and in the first windows I make a 2+2 calculation and I display this result in my first window in a qlabel and I would like to be able to display this result in my second window! how do I do it?

//seconde_p2.cpp
#include "seconde_p2.h"

#include "mainwindow.h"

#include "ui_seconde_p2.h"


seconde_p2::seconde_p2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p2)
{
    ui->setupUi(this);
    
    int a,b,c;
    a=2;
    b=2;
    c=a+b;
    ui->lineEdit->setText(QString::number(c)); 


}

seconde_p2::~seconde_p2()
{
    delete ui;
}

//seconde_p3.cpp
#include "seconde_p3.h"
#include "seconde_p2.h"

#include "ui_seconde_p3.h"


seconde_p3::seconde_p3(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p3)
{
    ui->setupUi(this);
    
     // how use c here 
}

seconde_p3::~seconde_p3()
{
    delete ui;
}

[SGaist]

Hi,

You can use Signals and Slots, or a simple setter, or pass the value as a parameter of the constructor.

[mrjj]

Hi
One way is to give it to the window when you create it.
Change its constructor to accept extra parameter
and give it to it when constructed.

int c= xxxx
seconde_p3 * win3 = new seconde_p3(this, c):
win3->show();

[Albator]

This post is deleted!

[Albator]

I try getter/setter :

in my first windows second_p2

// seconde_p2.h

    //getter
    int get_c() const{return c;}
    //setter
    void set_c(int val);

protected :
    int c;

// seconde_p2.cpp
seconde_p2::seconde_p2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p2)
{
    ui->setupUi(this);

    c=3;


}

yes for this example setter is useless and in my seconde page alias seconde_p3 i have :

// seconde_p3.cpp

seconde_p3::seconde_p3(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p3)
{
    ui->setupUi(this);



seconde_p2* test = new seconde_p2();
test->get_c();
qDebug()<< test;



}

i have 0 error but ! in the console i can look this :
seconde_p2(0x1bf26bf8, name="seconde_p2")

and it's not my c=3 :(

[Bonnie]

@Albator said in communicate data between two windows:

i have 0 error but ! in the console i can look this :
seconde_p2(0x1bf26bf8, name="seconde_p2")

and it's not my c=3 :(

[EDITED]
Sorry, didn't understand your code until now...

qDebug()<< test->get_c();

That should output a "3"

[Albator]

yes it's exact ! thanks all for your help ! :)))

[Albator]

i have a little problem, for a int it's okay but to make a getter with a qvector<double> it doesn't work.

seconde_p2.h
 //getter
    int get_c() const{return c;}
    QVector<double> get_vector() const{return fer;}
    //setter
    //void set_c(int val);

protected :
    int c=6;
    QVector<double> fer;

// seconde_p2.cpp
seconde_p2::seconde_p2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p2)
{
    ui->setupUi(this);

    c=3;
    fer={ 1, 2, 3, 4, 5, 6, 7 };


}

and in the seconde_p3.cpp

seconde_p3::seconde_p3(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p3)
{
    ui->setupUi(this);

seconde_p2* test = new seconde_p2();
seconde_p2* test1 = new seconde_p2();

test->get_vector();
qDebug()<<"qvector<double> display"<< test->get_vector();

test1->get_c();
qDebug()<<"int display"<< test1->get_c();


}

in the console :

qvector<double> display QVector() // why he is empty ?
int display 3

[Albator]

This post is deleted!

[mrjj]

Hi
Should work as you put value in the vector, in the constructor.

what does test->get_vector();
do ?

maybe you return empty list there ?

[Albator]

@Albator said in communicate data between two windows:

QVector<double> get_vector() const{return fer;}

and fer is not empty, it works for c ...

[Q139]

Is it wrong to use global window pointers and access setters getters via pointer instead of signals&slots?

[Albator]

i want use getter in first but if i have not the choice maybe i will change my solution, it works for c so it should work for the qvector

[mrjj]

@Albator
yes must also work for Qvector same way as int.

[Albator]

@mrjj
that's what I think, but who knows where the pangolin is that's standing in the way of my code?

[mrjj]

@Albator
so while it returns empty list and the same time in same code and
in same run, it can return 3 for c ?
it seems impossible :)

[Albator]

@mrjj
in first i put my value :

seconde_p2::seconde_p2(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p2)
{
    ui->setupUi(this);

    c=3;
    fer={ 1, 2, 3, 4, 5, 6, 7 };
    qDebug() << fer;


}

and in second i have a button who call the other windows :

void seconde_p2::on_page3_clicked()
{
    p3 = new seconde_p3(this);
    p3->show();
}

and for the final in the second_p3.cpp (my other window), i use my getter and display :

seconde_p3::seconde_p3(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::seconde_p3)
{
    ui->setupUi(this);

seconde_p2* test = new seconde_p2();
seconde_p2* test1 = new seconde_p2();

test->get_data1();
qDebug()<<"qvector<double> display"<< test->get_data1();

test1->get_c();
qDebug()<<"int display"<< test1->get_c();


}

and tadaaaa : c is displayed correctly and fer is empty
my conclusion ? it's a sad day :(

[Christian Ehrlicher]

@Albator said in communicate data between two windows:

seconde_p2* test = new seconde_p2();
seconde_p2* test1 = new seconde_p2();

C++ basics - this are new local instances - it won't help at all. You have to pass the pointer from the other object to this class. This is basic c++ stuff - programming with Qt without this basic knowledge will not work.

[Albator]

@Christian-Ehrlicher
excuse me I try and thanks to your advices I advance and yes sometimes I miss my bases :)