How declare a variable global to use in two forms?

[fayevalentine]

I want to know if anyone could help me:

I declare a global variable to use in a form, but I cannot access this variable from a diferent form.

How can I do it?

 

[onrdbandit]

Howdy,

The best way to do this is to make the "global" variable a property of the main TForm object. Then you simply include the header file for the main TForm object in the .cpp of the second form, and access it by
MainFormNamedWhatever->The"Global"VariableYouWantAccess

It is all rather simple, but if you need more detailed assistance, just give a haller...

Good luck,
onrdbandit

No! Try not. Do, or do not. There is no try. - Yoda

 

[butthead]

you might try the "extern" thingy

see "extern" in help files

Examples

extern int _fmode;

extern void Factorial(int n);

extern "c" void cfunc(int);

extern

Category

Storage class specifiers

Syntax

extern <data definition> ;

[extern] <function prototype> ;

Description

Use the extern modifier to indicate that the actual storage and initial value of a variable, or body of a function, is defined in a separate source code module. Functions declared with extern are visible throughout all source files in a program, unless you redefine the function as static.

The keyword extern is optional for a function prototype.

Use extern "c" to prevent function names from being mangled in C++ programs.

 

[kes103]

onrdbandit, your approach works for me to bring an EditVariable or a Label, etc. "back" into scope, but how about other variables used in the form class, how can they be brought into scope?

 

[kes103]

It looks like you can also declare the variable(s) in the header file for the form instead of under the event where your main calculations are.

 

[butthead]

you could also declare the variable above
winmain

#include <vcl.h>
#pragma hdrstop
USERES("Project1.res");
USEFORM("Unit1.cpp", Form1);

int GlobalVariable;

WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
{
try
{
Application->Initialize();
Application->CreateForm(__classid(TForm1), &Form1);
Application->Run();
}
catch (Exception &exception)
{
Application->ShowException(&exception);
}
return 0;
}

 

[kes103]

butthead, that doesn't seem to work for me.

 

[kes103]

Works best for me if I put the global variable(s)
right after #pragma hdrstop

#include <vcl.h>
#pragma hdrstop
//-------------------------------------------
int GlobalVariable(s);
//--------------------------------------------
USERES("Project1.res");
USEFORM("Unit1.cpp", Form1);



WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
{
try
{
Application->Initialize();
Application->CreateForm(__classid(TForm1), &Form1);
Application->Run();
}
catch (Exception &exception)
{
Application->ShowException(&exception);
}
return 0;
}

 

[Rached]

kes103 i think u need this for practice and an answer for ure first Q:

you can add your own variables and functions to the header file of your form. as a start do that by adding them to the public part, means you can have direct access to them from another form without that need for a function call.

assuming you have the first form called Form1 and it's headre file Unit1.h

public: // User declarations
__fastcall TForm1(TComponent* Owner);

//add here ure variables
int Unit1Var;

if you want to access this variable from another form, lets say Form2 with Unit2.h as it's header file then in that form include the .h file of Form1:

#include "Unit1.h"

in Form2 (as an example) you can get the variable by:
int Unit2Var = Form1->Unit1Var;
u'll figure out the rest