为什么出错

[mjpclab]

自定义一个类，但出错，我是凭c++的经验写的，可能有什么不对

type
.......

TPlate=class
public
Width,Height:byte;
constructor Create(tWidth,tHeight:byte);
end;

implementation

constructor TPlate.Create(tWidth,tHeight:byte);
begin
Width:=tWidth;
Height:=tHeight;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
p1,p2:TPlate;
begin
p1.Create(1,2);
p2.Create(3,4); //执行至此出错，代码窗口下方提示p1,p2尚未初始化

showmessage(inttostr(p1.Width));
showmessage(inttostr(p1.Height));
end;

[linzhisong]

var
p1,p2:TPlate;
begin
p1:= TPlate.Create(1,2);
p2:= TPlate.Create(3,4);

showmessage(inttostr(p1.Width));
showmessage(inttostr(p1.Height));
end;