Editing Object Pascal (section)

==Sample "Hello World" programs==
{{unreferenced section|date=June 2013}}
Here are several "Hello World" programs in different Object Pascal versions.

===Apple version===
<syntaxhighlight lang="objectpascal">
program ObjectPascalExample;

   type
      THelloWorld = object
         procedure Put;
      end;

   var
      HelloWorld: THelloWorld;

   procedure THelloWorld.Put;
   begin
      ShowMessage('Hello, World!');
   end;

begin
   New(HelloWorld);
   HelloWorld.Put;
   Dispose(HelloWorld);
end.
</syntaxhighlight>

===Turbo Pascal version===
Still supported in Delphi and Free Pascal. FPC also packages its own substitutes for the libraries/units. Delphi does not. The Free Pascal 1.0 series and the FPC textmode IDE are the largest open codebases in this dialect. Free Pascal 2.0 was rewritten in a more Delphi-like dialect, and the textmode IDE and related frameworks (Free Vision) are the only parts in the TP version of Object Pascal.

====Stack based allocation====
<syntaxhighlight lang="objectpascal">
program ObjectPascalExample;

   type
      THelloWorld = object
         procedure Put;
      end;

   procedure THelloWorld.Put;
   begin
      WriteLn('Hello, World!');
   end;

var
  HelloWorld: THelloWorld; { allocated on the stack and can be used without explicit allocation. }
begin
   HelloWorld.Put;
end.
</syntaxhighlight>

====Heap based allocation====
<syntaxhighlight lang="objectpascal">
program ObjectPascalExample;

   type
      PHelloWorld = ^THelloWorld;
      THelloWorld = object
         procedure Put;
      end;

   procedure THelloWorld.Put;
   begin
      WriteLn('Hello, World!');
   end;

var
  HelloWorld: PHelloWorld; { this is a typed pointer to a THelloWorld }

begin
   New(HelloWorld);
   HelloWorld^.Put;
   Dispose(HelloWorld);
end.
</syntaxhighlight>

Another example:

<syntaxhighlight lang="objectpascal">
program ObjectPascalExample;

   type
      PHelloWorld = ^THelloWorld;
      THelloWorld = object
         procedure Put;
      end;

   procedure THelloWorld.Put;
   begin
      WriteLn('Hello, World!');
   end;

var
  HelloWorld: PHelloWorld; { this is a typed pointer to a THelloWorld }
  HelloWorld2: ^THelloWorld; { this is exactly the same with different syntax } 
  HelloWorld3: ^THelloWorld;                               
  HelloWorld4: PHelloWorld;   
begin
   { This works in a similar way as the code above, note the allocation and de-allocation, though,
     many people get confused. In the past there was a wrong example with wrong comments here... }

   New(HelloWorld);  { one instance }
   HelloWorld4 := HelloWorld; { this is valid - a pointer copy }
   HelloWorld2 := HelloWorld; { this is valid - a pointer copy }
   New(HelloWorld3); { a second instance }
   HelloWorld4 := HelloWorld3; { this is valid - a pointer copy }
   HelloWorld2 := HelloWorld3; { this is valid - a pointer copy }
   Dispose(HelloWorld);  { it allocates only two instances }
   Dispose(HelloWorld3); { so it must release only two instances }
end.
</syntaxhighlight>

This works based on pointer copy, unless there is a specific allocation for a deeper copy.

===Delphi and Free Pascal version===
<syntaxhighlight lang="delphi">
program ObjectPascalExample;

type
  THelloWorld = class
    procedure Put;
  end;

procedure THelloWorld.Put;
begin
  Writeln('Hello, World!');
end;

var
  HelloWorld: THelloWorld;               { this is an implicit pointer }

begin
  HelloWorld := THelloWorld.Create;      { constructor returns a pointer to an object of type THelloWorld }
  HelloWorld.Put;
  HelloWorld.Free;                       { this line deallocates the THelloWorld object pointed to by HelloWorld }
end.
</syntaxhighlight>
Note that the object construct is still available in Delphi and Free Pascal.

===Oxygene version===
<syntaxhighlight lang="objectpascal">
namespace ObjectPascalExample;

   interface

   type
      ConsoleApp = class
         class method Main;
      end;

      THelloWorld = class
         method Put;
      end;

   implementation

   method THelloWorld.Put;
   begin
      Console.WriteLine('Hello, World!');
   end;

   class method ConsoleApp.Main;
   begin
      var HelloWorld := new THelloWorld;
      HelloWorld.Put;
   end;

end.
</syntaxhighlight>

===DWScript (Smart Pascal) version===
<syntaxhighlight lang="objectpascal">
type
   THelloWorld = class
      procedure Put;
      begin
         PrintLn('Hello, World!');
      end
   end;

var HelloWorld := THelloWorld.Create;
HelloWorld.Put;
</syntaxhighlight>

The method implementation can also be made in a distinct location as in other Object Pascal dialects.