C++ Can I use Identifiers in another class?

Question

I am new to C++ so I'm not sure how to do this. Basically I have some identifiers of type CEdit declared in PvUiSampleDlg.h. They are used in PvUiSampleDlg.cpp.

CEdit mIPEdit;
CEdit mMACEdit;
CEdit mManufacturerEdit;
CEdit mModelEdit;
CEdit mNameEdit;

What I have done is created another class called SettingsDlg.cpp and I want to use the same identifiers in this class as well. How do I go about doing this? I am assuming that you have to get the identifiers in the SettingsDlg.h but I am not sure how to do that. I have #include PvUiSample.h in both the SettingsDlg.cpp and SettingsDlg.h. Any help would be appreciated.

Answer 1

It looks like you're looking for the extern keyword.

When you declare your variables put extern infront of them. This lets the compiler/linker know that these variables will be used outside of this file.

//PvUiSampleDlg.h
extern CEdit mIPEdit;
extern CEdit mMACEdit;
extern CEdit mManufacturerEdit;
extern CEdit mModelEdit;
extern CEdit mNameEdit;

Make sure you only initialize your variables in one place.

//PvUiSampleDlg.cpp
#include "PvUiSampleDlg.h"

CEdit mIPEdit(/* your constructor args*/); // You can initialize like this
...
void someFunc(){
    return mIpEdit;  // do something with your variable as you would normally
}

You can initialize the your variable as seen above. Make sure you include the header containing your extern variables otherwise the initialization will treat it like a normal static variable.

Then in any other file including your header, you can use these variables as you would expect.