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Delphi XE: Is it possible to call virtual constructors with parameters from a typical type with restrictions of the classtype type without departing from the hack?

I am trying to create a common ancestor for composite controls. The initial idea looked something like this:

type
  TCompositeControl<TControl1: TControl; TControl2: TControl> = class(TWinControl)
  private
    FControl1,
    FControl2: TControl;
  public
    constructor Create(AOwner: TComponent); override; 
  end;

  TLabelAndEdit = TCompositeControl<TLabel, TEdit>; // simple example for illustration only

constructor TCompositeControl<TControl1,TControl2>.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  FControl1 := TControl1.Create(Self);
  FControl2 := TControl2.Create(Self);
end;

As you already know, this will cause an E2568 compiler error: it is not possible to create a new instance without the CONSTRUCTOR constraint in the type parameter declaration. Adding a constraint constructordoes not help, since it implies a constructor without parameters.

Casting templates into TControlcompiled code makes:

...
FControl1 := TControl(TControl1).Create(Self);
...

... but this leads to an access violation at runtime.

One hack that is likely to work calls the constructor via RTTI, but I would find this a rather dirty solution.

, , :

type
  TControlClass = class of TControl;

constructor TCompositeControl<TControl1,TControl2>.Create(AOwner: TComponent);
var
  lCtrlClass1,
  lCtrlClass2: TControlClass;
begin
  inherited Create(AOwner);
  lCtrlClass1 := TControl1;
  FControl1 := lCtrlClass1.Create(Self);
  lCtrlClass2 := TControl2;
  FControl2 := lCtrlClass2.Create(Self);
end;

? , - , classtype-constraint ?

+5
4

: TControl(TControl1).Create(Self). , TControl1 TControl, , . . -:

FControl1 := TControlClass(TControl1).Create(Self);
+6

FControl1 := TControl1(TControl1.NewInstance); // get memory for object
FControl1.Create(self); // call type-specific constructor

FControl2 := TControl2(TControl2.NewInstance); // get memory for object
FControl2.Create(self); // call type-specific constructor

Delphi Classes.pas:: CreateComponent , !

0

, delphi (), . , , DelphiXe8 delphi Seattle

0

(, TObject), , :

"

:

TCompositeControl < Control1: TControl, ; TControl2: TControl, p >= (TWinControl)

, .

Howether, , , .

, , .

-1

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