Question

How do I create a unit in order to call it after that by adding it to the uses clause of the implementation part of 3 other units?

When I first create a unit I see something like:

unit Unit1;

interface

implementation

end.

How do I put some variables which I am using in my script in order to re-call them from 3 other units (to avoid circular references)?

Answer 1

Global variables, classes, methods, constants, and public members defined in the Interface section are all available to reference in other units.

unit Unit1;

interface

const
  // Global constant
  MY_CONSTANT = 'FOO';

type TMyObject = class
private
  FMyProperty: String;
public
  // Public instance variable of class TMyObject
  myPublicInstanceVariable: String;
  // Public property of class TMyObject
  property MyProperty: String read FMyProperty;
end;

var
  // Global variable
  myStringVariable: String;

implementation

end.

Protected members are available from other units within an inherited class.

Unfortunately, the documentation in XE2 is rather sparse. If you had an earlier version of Delphi, everything you needed to know about the basics would be included in the online help.

Edit

My answer to this question gives more details about uses clauses and avoiding circular references:

How to manage circular references in delphi units?