如何在不释放内容的情况下释放对象列表

Question

>我有一个填充的 ObjectList。然后对象中的细节发生了变化。现在我需要释放对象列表，但当我这样做时，也会释放列表中的对象。如何在不释放对象本身的情况下释放此列表？

示例代码：

{Gets starting cards and put them into the correct rows}
//***************************************************************************
procedure TFGame.GetStartingCards;
//***************************************************************************
const
  ManaTypes : array [0..3] of string = ('Lava','Water','Dark','Nature');
var
   i: integer;
   z:integer;
   Cards: TObjectList<Tcard>;
begin
  Cards := TObjectList<TCard>.Create;
  z:=0;
  {add all tcards (Desgin ) to this list in order Lava,water,dark,nature }
  cards.Add(cardLava1);
  cards.Add(cardlava2);
  cards.Add(cardlava3);
  cards.Add(cardlava4);
  cards.Add(cardwater1);
  cards.Add(cardwater2);
  cards.Add(cardwater3);
  cards.Add(cardwater4);
  cards.Add(carddark1);
  cards.Add(carddark2);
  cards.Add(carddark3);
  cards.Add(carddark4);
  cards.Add(cardnature1);
  cards.Add(cardnature2);
  cards.Add(cardnature3);
  cards.Add(cardnature4);
 //get data from DB
  for i := 0 to Length(ManaTypes) - 1 do
  begin
    with adoquery1 do
    begin
      close;
      sql.Clear;
      sql.Add('SELECT TOP 4 * FROM Cards WHERE Color = "'+ManaTypes[i]+'" ORDER BY Rnd(-(1000*ID)*Time())');
      open;
    end;
      {return the result of everything for giving mana type.. }
     if adoquery1.RecordCount = 0 then
        Showmessage('Error no cards in db');
     adoquery1.First;
     while not adoquery1.Eof do
     begin
        cards[z].Cname := adoquery1.FieldByName('Name').AsString;
        cards[z].Ccost := adoquery1.Fieldbyname('Cost').AsInteger;
        cards[z].Ctext := adoquery1.FieldByName('Text').AsString;
        cards[z].Ccolor := adoquery1.FieldByName('Color').AsString;
        cards[z].Cinplay := false; //in the play area
        if adoquery1.fieldbyname('Power').asstring <> '' then
            cards[z].Cpower := adoquery1.FieldByName('Power').AsInteger;
        if adoquery1.fieldbyname('Def').asstring <> '' then
            cards[z].Cdef := adoquery1.FieldByName('Def').AsInteger;
        if adoquery1.FieldByName('Type').AsString = 'Spell' then
           cards[z].Cspell := true
        else
           cards[z].Cspell := false;
        if adoquery1.FieldByName('Target').AsString = 'yes' then
            cards[z].SetTargetTrue
        else
            cards[z].settargetfalse;
        //based on color change background
        cards[z].Background.LoadFromFile(format('%spics%s.png',[maindir,cards[z].Ccolor]));
       adoquery1.Next;
       cards[z].repaint;
       z:=z+1;
     end;
  end;
 //cards.Free; if i free this it removes all the cards added to it..
end;

Answer 1

TObjectList<T>的构造函数接收一个名为 AOwnsObjects 的参数，该参数指定谁负责释放对象。如果您传递True则列表具有该责任。否则，责任仍由您承担。

constructor Create(AOwnsObjects: Boolean = True); overload;

该参数的默认值为 True，我假设您在未指定该参数的情况下调用构造函数。因此，您将获得默认行为 - 列表拥有其成员。

文档是这样说的：

AOwnsObjects 参数是一个布尔值，指示对象条目是否归列表所有。如果对象是所有者，则从列表中删除该条目时，将释放该对象。属性是从此参数的值设置的。默认值为 true。

现在，如果您希望此特定列表实例不释放其成员，那么使用 TObjectList<T> 几乎没有什么好处。您不妨使用普通的旧TList<T>.