Calling vars from a DLL

Hello, I would Export Vars from a DLL and call them in my programm, example I would export S:String from a Dll and call that in another programm. Could you help me there??
k4hvd88Asked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

sftwengCommented:
It would be much better practice to export a Function call from the DLL that returns a value of the expected type (e.g., in this case, a string), or to make it a property of a class.

The history of software is strewn with defects caused by the use of "global" shared variables. That's why encapsulation is such a valuable concept.
0
gmayoCommented:
An example (DLL code first):

library Project2;

uses
  SysUtils,
  Classes;

{$R *.res}

var
      MyInt : integer = 999;
      MyStr : string = 'Hello, world!';

function GetMyInt : integer; stdcall;
begin
      Result := MyInt;
end;

procedure SetMyInt(v : integer); stdcall;
begin
      MyInt := v;
end;

function GetMyStr : PChar; stdcall;
begin
      Result := PChar(MyStr);
end;

procedure SetMyStr(s : PChar); stdcall;
begin
      MyStr := s;
end;

exports
      GetMyInt,
      SetMyInt,
      GetMyStr,
      SetMyStr;

begin
end.


...and the code to call it:

program Project1;

uses
  Dialogs, SysUtils;

{$R *.res}

const
      MyDLL = 'Project2.dll';

function GetMyInt : integer; stdcall; external MyDLL;
function GetMyStr : PChar; stdcall; external MyDLL;
procedure SetMyInt(v : integer); stdcall; external MyDLL;
procedure SetMyStr(s : PChar); stdcall; external MyDLL;

begin
      ShowMessage(GetMyStr);
      ShowMessage(IntToStr(GetMyInt));
      SetMyStr('Goodbye');
      SetMyInt(123);
      ShowMessage(GetMyStr);
      ShowMessage(IntToStr(GetMyInt));
end.


Geoff M.
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
k4hvd88Author Commented:
is there any method to call vars directly?
0
gmayoCommented:
I believe not. From Delphi help:

"Global variables declared in a shared library cannot be imported by a Delphi application.

A library can be used by several applications at once, but each application has a copy of the library in its own process space with its own set of global variables. For multiple libraries--or multiple instances of a library--to share memory, they must use memory-mapped files. Refer to the your system documentation for further information."

Geoff M.
0
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Delphi

From novice to tech pro — start learning today.