Arrays of functions help

bwcal1999

I am trying to make an array of functions and can't understand why this is not working. I get the following error when I compile.

error: cannot convert 'MainWindow::readMe' from type 'void (MainWindow::)()' to type 'arrayOfFunctions {aka void*}'
functions[i] = readMe;
^

Below is the code.

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>

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

MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::readMe()
{
    qDebug() << "I got read";
}

void MainWindow::on_pushButton_clicked()
{
    typedef void (*arrayOfFunctions);
    arrayOfFunctions  functions[10];

    for(int i = 0; i < 10; i++)
        functions[i] = readMe;


}

VRonin

try

void MainWindow::on_pushButton_clicked()
{
std::function<void()> functions[10];
for(int i = 0; i < 10; i++)
        functions[i] = std::bind( &MainWindow::readMe,this);
}

bwcal1999

@VRonin Nope, that just give a lot more errors.

VRonin

I tried it and it works. did you forget to #include <functional>?

bwcal1999

@VRonin Yes i included that.

I get the error
'function' is not a member of 'std' std::function<void()> functions[10];
^

VRonin

try this code:

#include <functional>
#include <QDebug>
class MyClass{
public:
    MyClass()=default;
    void on_pushButton_clicked()
    {
    std::array<std::function<void()>,10> functions;
    for(int i = 0; i < 10; i++)
            functions[i] = std::bind( &MyClass::readMe,this);
    for(int i = 0; i < 10; i++)
        functions[i]();
    }
    void readMe()
    {
        qDebug() << "I got read";
    }

};

int main()
{
MyClass tempClass;
tempClass.on_pushButton_clicked();
return 0;
}

It works for me... Make sure your pro file contains:

CONFIG += c++11

and re-run qmake

EDIT:
@Wieland is correct, std::array is preferable
There is so much C++11 here I'm having an overdose!

? Offline

Hi! Or use a lambda:

void MainWindow::sayHi()
{
    qDebug() << "Hi!";
}

void MainWindow::on_pushButton_clicked()
{
    auto const count{10};
    std::array<std::function<void()>,count> myArray;
    for (auto &i : myArray) {
        i = [=]() { this->sayHi(); };
    }
}

bwcal1999

@VRonin said in Arrays of functions help:

CONFIG += c++11

I am using QTCreator 5.5.1 and still get the same error. not a member of std with both function and bind.

Also with g++ it i get the same error.

VRonin

In Qt Creator click on build->run qmake after you put CONFIG += c++11 in your .pro file

bwcal1999

@VRonin yes I have done that several times.

VRonin

let's go C++11 mental!

try this code in your main.cpp commenting out all the rest that's already there and tell me if it works and if not what does it complain about

#include <functional>
#include <array>
#include <QDebug>
class MyClass{
public:
    void on_pushButton_clicked()
    {
    std::array<std::function<void()>,10> functions;
    std::fill(std::begin(functions),std::end(functions),std::bind( &MyClass::readMe,this));
    for(const auto& i : functions)
        i();
    }
    void readMe()
    {
        qDebug() << "I got read";
    }

};
int main()
{
MyClass tempClass;
tempClass.on_pushButton_clicked();
return 0;
}

VRonin

This is the C++98 version of the code above

#include <QDebug>

class MyClass{
public:

    void on_pushButton_clicked()
    {

    void (MyClass::*functions[10])() ;
    for(int i = 0; i < 10; ++i)
        functions[i] = &MyClass::readMe;
    for(int i = 0; i < 10; ++i)
        (this->*functions[i])();
    }
    void readMe()
    {

        qDebug() <<  "I got read";
    }

};

int main(int argc, char **argv)
{
MyClass tempClass;
tempClass.on_pushButton_clicked();
return 0;
}

? Offline

@VRonin This is so retro, i want to watch Miami Vice on VHS now :-D

SGaist

@Wieland Starwars on Super 8mm ;)

@bwcal1999 What Qt version, compiler (including version), OS are you using ?

kshegunov

@VRonin said in Arrays of functions help:

void (MyClass::*functions[10])() ;

I hope you acknowledge most of us dinosaurs will typedef that. We are not masochists, only old-fashioned. ;)

? Offline

@VRonin said in Arrays of functions help:

let's go C++11 mental!

Okay :-)

void MainWindow::on_pushButton_clicked()
{
    std::array<std::function<void()>, 10> f;
    std::fill(std::begin(f), std::end(f), [=](){this->sayHi();});
    std::for_each(std::begin(f), std::end(f), [](auto &i){i();});
}