Delphi Basics : Do command

Delphi Basics
Do Keyword	Defines the start of some controlled action

1. for   Variable := Expression to Expression do Statement;
2. while Expression do Statement
3. try   Statements except on ExceptionClass do Statement; end;
4. with  Expression do Statement

Description

The Do keyword is always a part of one of the shown 4 control types. It precedes the Statements section of the control action.

Related commands

Begin		Keyword that starts a statement block
End		Keyword that terminates statement blocks
Except		Starts the error trapping clause of a Try statement
For		Starts a loop that executes a finite number of times
Repeat		Repeat statements until a ternmination condition is met
Try		Starts code that has error trapping
While		Repeat statements whilst a continuation condition is met
With		A means of simplifying references to structured variables

Example code : Show singles and block do statement blocks

// Full Unit code.
// -----------------------------------------------------------
// You must store this code in a unit called Unit1 with a form
// called Form1 that has an OnCreate event called FormCreate.

unit Unit1;

interface

uses
  SysUtils,
  Forms, Dialogs;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation
{$R *.dfm} // Include form definitions

procedure TForm1.FormCreate(Sender: TObject);
var
  i : Integer;

begin
  // A for statement - the do keyword precedes a single statement
  for i := 1 to 3 Do
    ShowMessage('For loop, i = '+IntToStr(i));

  // A while statement - the do precedes a statement block
  while i < 6 Do
  begin
    ShowMessage('While loop, i = '+IntToStr(i));
    Inc(i);
  end;
end;

end.

Hide full unit code

   For loop, i = 1
   For loop, i = 2
   For loop, i = 3
   While loop, i = 4
   While loop, i = 5