Calling structure object with QString or string

Question

I would like to take result from object of struct.

allitems.h

#ifndef ALLITEMS_H
#define ALLITEMS_H
#include <QString>
class allitems
{
public:
    allitems();
    struct magazalar{
        QString rev;
    }kfc;
};
#endif // ALLITEMS_H

item.cpp

#include "allitems.h"
allitems::allitems()
{
    kfc.rev="2";
}

now I would like to take result of kfc.rev from another cpp file

void MainWindow::clicked(){
    allitems aaa;
    QPushButton *xx=(QPushButton *)sender();
    //xx->objectName() returns "kfc"
    qDebug()<<aaa.(xx->objectName()).rev;
}

I would like to call kfc.rev with clicking button. when I clicked the button button objectname is kfc I can take as a result but I couldnt achieve to call struct data from button objectnames

Any idea to solve it?

You can not access a member with its name as string :aaa.(xx->objectName()).kat. — seleciii44
– seleciii44, Commented Dec 27, 2017 at 10:29
I'm sorry I just make mistake. I just edited. It is not kat, it should be rev — Kerem
– Kerem, Commented Dec 27, 2017 at 10:30
Is there anyway to convert string to member type? @seleciii44 — Kerem
– Kerem, Commented Dec 27, 2017 at 10:37
you could use a map(std::map or QMap) but that requires all of your members to be the same type (or at least same polymorphic base) — seleciii44
– seleciii44, Commented Dec 27, 2017 at 10:41

marcinj · Accepted Answer · 2017-12-27 10:28:47Z

3

You cannot do like that:

qDebug()<<aaa.(xx->objectName()).kat;

it is not valid C++, this: (xx->objectName()) must be known at compile time, not at runtime. If you want to make it work at runtime, you would need to use a map, or if statements:

here you can use simple if-s:

if (xx->objectName() == "kfc")
 qDebug()<<aaa.kfc.kat;
//else if (xx->objectName() == "some_other_kfc")
// qDebug()<<aaa.some_other_kfc.kat;

but I dont think its best design, usually you associate with a button a click handler which knows which structure to modify - and it does not need to derive this knowledge from the button instance.

answered Dec 27, 2017 at 10:28

marcinj

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3 Comments

Kerem Over a year ago

yes I can use the if statements but I will have more than 30 buttons I dont want to write other 30 different if statements so I have to access member with using object name of button.

marcinj Over a year ago

You may add to allitems method which will return magazalar by name, like: magazalar& getData(QString name) { if (name == "kfc") return kfc; .... }. C++ does not support (yet) reflection.

Kerem Over a year ago

I will try your approach but I think my problem occurs because the invalid calling of member. I have to convert the QString (xx->objectName() ) to someting that I can access to struct member kfc.rev I dont know what should I need to convert to.

Kuba hasn't forgotten Monica · Accepted Answer · 2017-12-27 18:44:27Z

0

The use of sender() is bad code smell, usually, and indicates that you should be doing something else instead.

In modern C++, you can easily generate the necessary code when you connect the buttons. Let's assume that aaa is a member of MainWindow:

MainWindow::MainWindow(QWidget * parent) : QMainWindow(parent) {
  auto const clicked = &QPushButton::clicked;
  connect(ui->kfc, clicked, [this]{ qDebug() << this->aaa.kfc.rev; });
  //more connect statements here...
}

answered Dec 27, 2017 at 18:44

Kuba hasn't forgotten Monica

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