Question

我想创建一个包含（ao）两个属性ObjectLinks和ObjectBacklinks的Tinterfacedobject。 Objectlinks包含对其他对象的接口引用，ObjectBacklinks包含这些链接的反向

两个属性都包含一个TWeakIntfDictionary = class（TDictionary） Backlinks属性在ObjectLinks.ValueNotify事件

中维护

为了确保在原始对象被释放时从字典中删除接口引用，通知算法（与TFmxObject使用的相同）将被放置到位

怀疑我在创建对同一个interfacedobjects的这么多引用时遇到各种循环引用问题:(但我似乎无法摆脱这个问题。当从被破坏的对象调用FreeNotification时一切顺利，直到从FreeNOtification返回。此时再次调用对象的.Destroy： - （

 {1 Dictionary of interfaces (using weak references) using Free notification }
  TWeakIntfDictionary = class(TDictionary<int64, IInterface>, IFreeNotificationMonitor)
  protected
    procedure ValueNotify(const Value: IInterface; Action: TCollectionNotification); override;
  public
    procedure FreeNotification(aObject: TObject);
  end;

  implementation

  procedure TWeakIntfDictionary.FreeNotification(aObject: TObject);
  var
    lObj: TPair<int64, IInterface>;
  begin
    //Object is going to be destroyed, remove it from dictionary
    for lObj in Self do
    begin
      if (lObj.Value as TObject).Equals(aObject) then
      begin
        Remove(lObj.Key);
        Break;
      end;
    end;
  end;

  procedure TWeakIntfDictionary.ValueNotify(const Value: IInterface; Action: TCollectionNotification);
  var
    lDestrIntf: IFreeNotificationBehavior;
  begin
      // When a TObject is added to the dictionary, it must support IDestroyNotification
      // This dictionary is than added to the notificationlist of the TObject
    if Supports(Value, IFreeNotificationBehavior, lDestrIntf) then
      case Action of
        cnAdded:      begin
                        lDestrIntf.AddFreeNotify(Self);
                        lDestrIntf._Release;
                      end;
        cnRemoved,
        cnExtracted:  begin
                        lDestrIntf.RemoveFreeNotify(Self);
                      end;
      end
    else
      raise EWeakInftDictionaryException.Create('Object added to TWeakIntfDictionary does not support IFreeNotificationBehavior');

    inherited;

  end;

任何人都知道WeakReferences词典的现有实现？有人建议如何解决这个问题？

Answer 1

在以下代码中找到解决方案

procedure TWeakIntfDictionary.FreeNotification(aObject: TObject);
var
  ...
begin
  //Object is going to be destroyed, remove it from dictionary
  lSavedEvent := FDict.OnValueNotify;
  FDict.OnValueNotify := nil;
  lRemoveList := TList<TKey>.Create;
  try
    for lPair in FDict do
    begin
      pointer(lIntf) := lPair.Value;
      if (lIntf as TObject) = aObject then
        lRemoveList.Add(lPair.Key);
    end;
    pointer(lIntf):=nil; // avoid _release for the last item

    for lKey in lRemoveList do
      FDict.Remove(lKey);

  finally
    FDict.OnValueNotify := lSavedEvent;
    lRemoveList.Free;
  end;
end;

如何在delphi中创建包含对接口的弱引用的TDictionary

1 个答案: