[讨论] 你所不知道的inherited

[ZuoBaoquan]

我们直奔主题，看看下面这段代码，你觉得程序的运行结果是什么？

program TestInherited;

{$APPTYPE CONSOLE}

uses
  SysUtils, Dialogs;

type
  TBase = class
  public
    constructor Create; overload;
    constructor Create(value: Integer); overload;
  end;

  TDerived = class(TBase)
  public
    constructor Create(value: Boolean = False); overload;
  end;

{ TBase }

constructor TBase.Create;
begin
  ShowMessage('TBase.Create');
end;

constructor TBase.Create(value: Integer);
begin
  ShowMessage('TBase.Create(value: Integer)');
end;

{ TDerived }

constructor TDerived.Create(value: Boolean);
begin
  inherited;
  ShowMessage('TDerived.Create');
end;

var
  example: TDerived;

begin
  try
    example := TDerived.Create;
    try
      // do nothing  
    finally
      example.Free;
    end;
  except
    on E:Exception do
      Writeln(E.Classname, ': ', E.Message);
  end;
end.

[ZuoBaoquan]

Yeah，回答正确！
我在使用Delphi2009泛型容器的时候，发现了几个严重Bug。其中一个就是因为TObjectList<T>使用inherited而导致没有正确初始化。

详见：Delphi 2009 泛型容器的两个严重Bug及深入分析
http://www.cnblogs.com/baoquan/archive/2009/01/03/1367702.html

[datm]

因为Create后面的参数类型不一致，所以不会区执行TBase.Create

[gwhdaxia]

inherited; 如果后面没有指定参数，那么就会找父类的相同名称，相同参数，
TBase里没有constructor Create(value: Boolean = False); 所以TBase里没找到相同的，

所以结果只是出现个'TDerived.Create '


如果指定了，就找指定的，比如说
constructor TDerived.Create(value: Boolean);
begin
inherited Create ;
ShowMessage('TDerived.Create');
end;

这里才先执行TBase.Create;
结果就是
'TBase.Create'
'TDerived.Create '

[starluck]

program TestInherited;

{$APPTYPE CONSOLE}

uses
SysUtils, Dialogs;

type
TBase = class
public
constructor Create; overload;
constructor Create(value: Integer); overload;
end;

TDerived = class(TBase)
public
constructor Create(value: Boolean = False); overload;
end;

{ TBase }

constructor TBase.Create;
begin
ShowMessage('TBase.Create');
end;

constructor TBase.Create(value: Integer);
begin
ShowMessage('TBase.Create(value: Integer)');
end;

{ TDerived }

constructor TDerived.Create(value: Boolean);
begin
inherited;
ShowMessage('TDerived.Create');
end;

var
example: TDerived;

begin
try
example := TDerived.Create;
try
// do nothing
finally
example.Free;
end;
except
on E:Exception do
Writeln(E.Classname, ': ', E.Message);
end;
end.


只会 ShowMessage('TDerived.Create');

如果 inherited create；的话，将继承基类的CREATE事件

[budded]

正常现象

[深宇]

那两个严重BUG在3379版本里已经修复了