How Can i get array in another class

dziko147

Hello ,
I created a public array in class A .
I want to get this array in class B .

so this is my code .

In class A.h

std::array<QString,25> Inputs;

In class A.cpp

int compteur=0;
QString cell0;
QString cell3 ;
for(int i=0;i<ui->tablewidget->rowCount();i++){

QTableWidgetItem *cell7 = ui->tablewidget->item(i,7);

QVariant myData7 = cell7->data(Qt::DisplayRole);
if (myData7=="Core_meas"){
cell0 = ui->tablewidget->item(i,0)->text();
cell3 = ui->tablewidget->item(i,3)->text();
Inputs[compteur]=cell3;
qDebug() << "Inputs baby"<<Inputs[compteur] ;
compteur++;
}

In class B :

I create instance of Class A then I called the array but I get it null .

this what I did :
In class B.h

#include "classA.h"

ClassA myclassA ;

In class B.cpp

for(size_t i=0;i<myclasseA.Inputs.size();i++){
myclasseA.Inputs[i];
qDebug() << "this is data",myclasseA.Inputs[i]

I get outputs :

this is data : ""

What I did wrong .
Or How can I do this correctly
thankyou

SGaist

Hi,

What exactly do you want to do ?

Class A seems to be a widget that you likely instanciate somewhere. You likely instanciate an object of class B somewhere else and thus these are two different objects of class A.

What exactly are you trying to do ?

dziko147

@SGaist
yes , exact class A is a widget .I uploaded a csv file then extract some data from it and put it in Inputs[] using this code :

int compteur=0;
QString cell0;
QString cell3 ;
for(int i=0;i<ui->tablewidget->rowCount();i++){

QTableWidgetItem *cell7 = ui->tablewidget->item(i,7);

QVariant myData7 = cell7->data(Qt::DisplayRole);
if (myData7=="Core_meas"){
cell0 = ui->tablewidget->item(i,0)->text();
cell3 = ui->tablewidget->item(i,3)->text();
Inputs[compteur]=cell3;
qDebug() << "Inputs "<<Inputs[compteur] ;
compteur++;
}

So I would like to get the Inputs[] in my class B .

I create a classA instance in class B .

ClasseA myclasseA; // in classB.h
//then i tried to get Inputs[] using this code
for(size_t i=0;i<myclasseA.Inputs.size();i++){
myclasseA.Inputs[i];
qDebug() << "this is data",myclasseA.Inputs[i]

So my question is what i have missed .? Or how can i do this correctly .

SGaist

What is class B supposed to be doing ?

dziko147

@SGaist I will manipulate a CAN bus (send and receive frame) using data in inputs[].

Anonymous_Banned275

@dziko147 I am doing similar task - passing data between classes and trying to use "connect". In my case the "parent " class" is a "form" and the "child" class is a widget - dialog.
I do not have it fully solved.
I can use QDesigner "go to slot" , but so far only within the class.
I found a bug ( submitted and acknowledged as bug ) in "go to slot" and trying to hack around it for now.
Is that something - connect - which would work for you?

dziko147

@AnneRanch what type variable you passed please !

dziko147

This post is deleted!

CP71

@dziko147
Hi,
I tried doing make the same thing and I didn't see anything wrong.
Are you sure the fill function is called?
Are you sure that you don't have two instances of the class?

Class1.h
public:
std::array<QString,25> Inputs;

Class1.cpp
Class1::Class1(QObject *parent) : QObject(parent)
{
for( int i=0; i<25; i++)
{
Inputs[i] = 'a'+i;
}
}
Class2.h
protected:
Class1 *myClass;

Class2.cpp
Class2::Class2(QObject *parent) : QObject(parent)
{
myClass = new Class1();
for ( int i=0; i<25; i++)
qDebug() << myClass->Inputs[i];
}
My output
"a"
"b"
"c"
"d"
"e"
"f"
"g"
"h"
"i"
"j"
"k"
"l"
"m"
"n"
"o"
"p"
"q"
"r"
"s"
"t"
"u"
"v"
"w"
"x"
"y"

dziko147

@CP71 said in How Can i get array in another class:

protected:
ClassChield *chield;

can you explain me what did this ?

CP71

@dziko147
My mistake, I have corrected my previous post.
In my example project the classes have different names
Sorry

dziko147

@CP71 thanks for your reply .
I used your solution but still get array empty.

I set data in Inputs in a Slot called after clicking in button .
It cause problem ?

void UploadCSV::on_parambtn_2_clicked()
{

    int compteur=0;
    QString cell0;
    QString cell3 ;
    for(int i=0;i<ui->tablewidget->rowCount();i++){

        QTableWidgetItem *cell7 = ui->tablewidget->item(i,7);

        QVariant myData7 = cell7->data(Qt::DisplayRole);
        if (myData7=="Core_meas"){
            cell0  = ui->tablewidget->item(i,0)->text();
            cell3 = ui->tablewidget->item(i,3)->text();
            Inputs[compteur]=cell3;
            qDebug() << "Inputs baby"<<Inputs[compteur] ;
            compteur++;
        }

    }


}

CP71

@dziko147
I suppose you see a valid values in array at line:
qDebug () << "Inputs baby" << Inputs [compteur];

If yes, the only thing I think is a double instance of the class, but surely you have already checked it.

I don't have other ideas :(

Anonymous_Banned275

@dziko147 At current state of the project I need only a text (QTString ) - basically address and name of local , connected to PC, Bluetooth device.
That data is a result of my dialog "scan" for local Bluetooth adapters. .

Since it is such small amount of data I am currently NOT using "connect".
Eventually I am going to use connect to pass real data from the dialog to the form.

I started using "go to slot" feature , however I have not figured out how to use it "between objects ".
It is interesting feature but so far only good to "pass data" in same object.

It has an optional "parameter", but I not found how to use it.

So in summary - using "go to slot" should be able to pass data between objects - as you desire . But I need to study it more.

PS
Passing data between objects seems to be subject of many discussions.
The way I see it - it is two step process - you have to collect the data (obviously) using "connect" triggered by the data event. . Then use second "connect " to pass the captured data between objects.

dziko147

@AnneRanch if you need just a Qstring to pass it . I recommend using signal/Slot .

SGaist

@dziko147 you should go back to the basics first: séparation of responsibilities.

There's no reason for you child class to have an instance of your GUI class in it.

From the looks of it, your GUI is responsible to generate that array and it looks as well as the class processing that array should receive it from the GUI object. Hence there's no need for it to know anything or contain an object of your GUI class.

dziko147

@SGaist exact. I set data in my array from GUI element .
if i understand you. I don't need to create an instance of my class .
So how can i call the array from the other class

anh_ph

If class B is child of class A, then you can do sth like this in class B

classA *clsA= dynamic_cast <classA*> (parent());
clsA->funcToGetData();

dziko147

@anh_ph the funcToGetData(); can be a slot wich get data from GUI elements ?

And if classA isn't child od classB . How can i call it

JonB

@dziko147 said in How Can i get array in another class:

And if classA isn't child od classB . How can i call it

The code you were shown attempts to cast the parent() to classA. If your classA instance is not related to you classB instance through its parent, then use whatever you have for the desired classA instance....

I'm not sure but you seem not to understand the difference between a class and an instance (or object)? If that is the case I suggest you read up to understand, as this is vital in OO programming.