理解Delphi的类(五)

先新建一个 VCL Forms Application 工程, 代码中就已经出现了两个类:

一个是 TForm 类; 一个是 TForm1 类; TForm1 继承于 TForm.

TForm 是 TForm1 的父类; TForm1 是 TForm 的子类.

unit Unit1;
interface
uses
　Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
　Dialogs, StdCtrls;
type
　TForm1 = class(TForm)
　　Button1: TButton;
　　Button2: TButton;
　　procedure Button1Click(Sender: TObject);
　　procedure Button2Click(Sender: TObject);
　end;
　//下面自定义了两个类, TChild 继承于 TBass
　TBass = class
　　procedure msg1;
　end;
　TChild = class(TBass)
　　procedure msg2;
　end;
var
　Form1: TForm1;
implementation
{$R *.dfm}
{ TBass }
procedure TBass.msg1;
begin
　ShowMessage('is Bass');
end;
{ TChild }
procedure TChild.msg2;
begin
　ShowMessage('is Child');
end;
//测试1: 父类只有一个方法 msg1
procedure TForm1.Button1Click(Sender: TObject);
var
　b: TBass;
begin
　b := TBass.Create;
　b.msg1; {is Bass}
　b.Free;
end;
//测试2: 子类有两个方法, 自己一个 msg2, 还继承了一个 msg1
procedure TForm1.Button2Click(Sender: TObject);
var
　c: TChild;
begin
　c := TChild.Create;
　c.msg1; {is Bass}
　c.msg2; {is Child}
　c.Free;
end;
end.