How to access Main Window's members from an object belongig to a user defined class

[marcel]

Actually, it is more like a recursive inclusion. Population includes main window, and the other way around.

Add ifdefs to population.h too to make it compile only once.
Something like:

#ifndef POPULATION_H
#define POPULATION_H
 
//class declarations, etc
 
#endif

#ifndef POPULATION_H
#define POPULATION_H

//class declarations, etc

#endif

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Also, in Ui_mainwindow.h, if possible, store a pointer to Population and include population.h in the cpp only.

Regards