覆盖虚方法

unit Unit1;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
  {自定义父类}
  TParent = class
    protected
      function MyFun(i:Integer):Integer; dynamic;  //动态方法
      procedure MyProc; virtual;  //虚拟方法
  end;
  {自定义子类}
  TChild = class(TParent)
    protected
      function MyFun(i:Integer):Integer; override;   //覆盖父类的同名动态方法
      procedure MyProc; override;
  end;
var
  Form1: TForm1;

implementation

{$R *.dfm}

{ TParent }

function TParent.MyFun(i: Integer): Integer;   //功能，对函数参数+1
begin
  inc(i);
  Result:=i;
end;

procedure TParent.MyProc; //功能，显示一个字符串'TParent'
begin
  ShowMessage('TParent');
end;

{ TChild }

function TChild.MyFun(i: Integer): Integer;  //功能，调用父类的MyFun方法后再+1
begin
  i:=inherited MyFun(i);
  inc(i);
  Result:=i;
end;

procedure TChild.MyProc;  //功能，调用父类的MyProc方法后再显示另一个字符串'TChild'
begin
  inherited;
  ShowMessage('TChild');
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  p:TParent;
  c:TChild;
begin
  p:=TParent.Create;
  c:=TChild.Create;

  p.MyProc;  //Parent
  c.MyProc;  //Parent; TChild

  ShowMessage(IntToStr(p.MyFun(2)));  //3
  ShowMessage(IntToStr(c.MyFun(2)));  //4

  p.Free;
  c.Free;
end;

end.