Datasnap和TObject参考

Question

如何处理datasnap服务器中的对象引用？

我有返回TUser对象的Datasnap服务器方法

TServerMethods.CurrentUser(const AId: Integer): TUser
begin
  Result := GlobalCurrentUser; // <- Don't want to free this object
  Result.AddReference;
end;

TReferencedObject的子类中的TUser

TReferencedObject = class(TObject)
private
  FReferenceCnt:     integer;
public
  procedure AddReference; virtual;
  procedure RemoveReference; virtual; // Frees object if reference count goes to 0
  property ReferenceCnt: integer Read FReferenceCnt Write FReferenceCnt;
end;

目前，DataSnap服务器释放了TUser对象，但我想为TReferencedObject后代调用RemoveReference。

Answer 1

我将DataSnap文件Data.DBXJSONReflect.pas和Datasnap.DSReflect.pas复制到项目目录中，添加到项目中，并做了三处修改。

设置正确ReferenceCount的Data.DBXJSONReflect中的两个更改

1) TJSONUnMarshal.CreateObject

  if HasObject(ObjId) then
  begin
    Obj := GetObject(ObjId);
    if Obj is TReferencedObject then {Framework}
      TReferencedObject(Obj).AddReference; {Framework}    
    exit(Obj);
  end

2) TJSONPopulationCustomiser.PostPopulate

  if Data is TReferencedObject then {Framework}
    TReferencedObject(Data).AddReference; {Framework}

Datasnap.DSReflect发布参考中的一处更改

1) TDsMethodValues.ClearReferenceParameters

将FUserObject.Clear更改为ClearUserObjects(FUserObjects);，并添加本地函数

  procedure ClearUserObjects(const AUserObjects: TObjectList<TObject>); {Framework}
  var
    i: Integer;
  begin
    FUserObjects.OwnsObjects := False;
    for i := FUserObjects.Count - 1 downto 0 do
      if FUserObjects.Items[i] is TReferencedObject then
      begin
        TReferencedObject(FUserObjects.Items[i]).RemoveReference;
        FUserObjects.Delete(i);
      end;
    FUserObjects.OwnsObjects := True;
    FUserObjects.Clear;
  end;