如何从 mainwindow.cpp 中的函数访问 main.cpp 中的变量？

Question

I click button and want change some variables in main.cpp. How access it from function in mainwindow.cpp.

void MainWindow::on_spinBox_valueChanged(int coef)
{
   //here I need x=coef;
   //x is in main.cpp
}

Answer 1

As explained in the comments, it is better to change the architecture of your program. However, if you still want to opt for a simple solution, you can use the external variables:

Declare x in your file main.cpp out of main function:

#include ...  

int x;

int main ()...  

In your mainwindow.cpp , declare your x as extern in global scope:

extern int x;  
void MainWindow::on_spinBox_valueChanged(int coef) 
{
   x = coef;
}