对delphi的Create,inherited,AfterConstruction的流程了解及测试

来源：互联网发布：数据备份方案编辑：程序博客网时间：2024/05/22 03:47

写了一个测试代码, 创建一个窗体拉上一个按钮控件,复制以下的代码

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;
  C1 = class //(TPersistent) 
  private
    p1:string;
  public
    procedure Show;
    procedure AfterConstruction; override;
    procedure BeforeDestruction; override;
    constructor Create; virtual;
    procedure test(str: string);
  end;
  C2 = class(C1)
  public
    constructor Create; override;
    constructor CreateNew; virtual;
    procedure AfterConstruction; override;
    procedure Show;
  end;
  C3 = class(c2)
  end;
var
  Form1: TForm1;
implementation
{$R *.dfm}
{ C1 }
procedure C1.AfterConstruction;
begin
  inherited AfterConstruction;
  test('C1.AfterConstruction'); ;
end;
procedure C1.BeforeDestruction;
begin
  test('C1.BeforeDestruction'); ;
  inherited BeforeDestruction;
end;
constructor C1.Create;
begin
inherited;
  test('C1.Create');
end;
procedure C1.Show;
begin
  ShowMessage(p1);
end;
procedure C1.test(str: string);
begin
  ShowMessage(str);
end;
{ C2 }
procedure C2.AfterConstruction;
begin
  inherited;
  ShowMessage('C2.AfterConstruction');
end;
constructor C2.Create;
begin
  inherited Create;
  test('c2.Create'); ;
end;
constructor C2.CreateNew;
begin
  Create;
  test('c2.CreateNew');
end;
procedure C2.Show;
begin
  inherited Show;
  test('c2.show');
end;
procedure TForm1.Button1Click(Sender: TObject);
var
  a: c3;
  b: c2;
  c:c1;
  begin
  c:=c3.CreateNew;
  c.p1:='aaa';
  c.Show;
  c.test('aaaaa');
end;
end.

单击按钮时,依次显示:

C1.Create // 运行了c:=c3.CreateNew; inherited Create;

C2.Create //Create;

C2.CreateNew

C1.AfterConstruction C2.AfterConstruction 里的inherited

C2.AfterConstruction

aaa

aaaaa

在对象创建前会自动调用AfterConstruction,资料参考空间里之前发布的文章