为何创建对像时不会调用构造函数？
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls,Unit2;

type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
a:ta;
begin
a:=ta.Create;
a.Free;
end;

end.
==========================
unit Unit2;

interface
uses
Windows, Messages, SysUtils, Variants, Classes;

type
ta=class(tobject)
private
constructor create;overload;
destructor destroy;override;
end;
implementation

{ ta }

constructor ta.create;
begin
inherited;
messagebox(0, 'a', 'a', 0);
end;

destructor ta.destroy;
begin
messagebox(0, 'b', 'b', 0);
inherited;
end;

end.
==================
这是全部代码，为何在按按钮时，不会调用构造函数呢？

[解决办法]
ta=class(tobject)
private ->改成public

[解决办法]
不要把constructor create;overload; destructor destroy;override; 写在Private段里