OOP - Image Movement

I am just starting to learn delphi, in particular in school we have been doing Classes. I thought i'd give it a go trying to make an object move around using the arrow keys.

So Far this is my Class Definitions.

"unit ClassDefs;

interface

uses
Classes, StdCtrls, Buttons;

type
TCar = Class
Private
inX : Integer;
inY : Integer;
Public
Procedure UpKey;
Procedure DownKey;
Procedure LeftKey;
Procedure RightKey;
Function XPosition : Integer;
Function YPosition : Integer;
Function GetinX : Integer;
Function GetinY : Integer;
End;

implementation

Function TCar.XPosition;
begin
Result := inX;
end;

Function TCar.YPosition;
begin
Result := inY;
end;

Procedure TCar.UpKey;
begin
inY := inY + 1;
end;

Procedure TCar.DownKey;
begin
inY := inY - 1;
end;

Procedure TCar.LeftKey;
begin
inX := inX - 1;
end;

Procedure TCar.RightKey;
begin
inX := inX + 1;
end;


Function TCar.GetinX : Integer;
begin
Result := inX;
end;

Function TCar.GetinY : Integer;
begin
Result := inY;
end;

end."


And then this is my main Program.



"unit RaceUnit1;

interface

uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, ClassDefs , Vcl.Dialogs, Vcl.ExtCtrls,
Vcl.Imaging.pngimage;

type
TfrmRace = class(TForm)
imgRacecar: TImage;
procedure FormCreate(Sender: TObject);
procedure FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);
private
public
end;

var
frmRace: TfrmRace;
Car : TCar;

implementation

{$R *.dfm}

procedure TfrmRace.FormCreate(Sender: TObject);
begin
imgRacecar.Left := 10;
imgRacecar.Top := 10;
end;



procedure TfrmRace.FormKeyDown(Sender: TObject; var Key: Word;
Shift: TShiftState);
begin
case Key of
VK_UP : Car.UpKey;
VK_DOWN : Car.DownKey;
VK_LEFT : Car.LeftKey;
VK_RIGHT : Car.RightKey;
end;
imgRacecar.Top := Car.XPosition;
imgRacecar.Left := Car.YPosition;
end;

end."


So far I have managed to get the movement working without Using Classes, but whenever I put it into a Class it doesn't seem to work. Now after playing around with it for an hour or so i've decided to rest and seek Help.

As far as I can see, in the code you posted, you never actually create a car object.

Thanks, just as a further question. Do you know how i would create the Car Object as an Image Class.

There are a number of different approaches you could take.
One as you suggest, inheriting from TImage.
Another would be passing a pointer to TImage inside TCar (but that is for another day).

Taking your original question and (with no testing) hopefully getting it right

Something like this:


Clive