Problem with typecast in Delphi XE - delphi

Question

I try to do list of procedures this way:
type
TProc = procedure of object;
TMyClass=class
private
fList:Tlist;
function getItem(index:integer):TProc;
{....}
public
{....}
end;
implementation
{....}
function TMyClass.getItem(index: Integer): TProc;
begin
Result:= TProc(flist[index]);// <--- error is here!
end;
{....}
end.
and get error:
E2089 Invalid typecast
How can I fix it?
As I see, I can make a fake class with only one property Proc:TProc; and make list of it. But I feel that it's a bad way, isn't it?
PS: project have to be delphi-7-compatible.

Answer 1

The typecast is invalid because you can not fit a method pointer to a pointer, a method pointer is in fact two pointers first being the address of the method and the second being a reference to the object that the method belongs. See Procedural Types in the documentation. This will not work in any version of Delphi.

Answer 2

Sertac has explained why your code doesn't work. In order to implement a list of such things in Delphi 7 you can do something like this.
type
PProc = ^TProc;
TProc = procedure of object;
TProcList = class(TList)
private
FList: TList;
function GetCount: Integer;
function GetItem(Index: Integer): TProc;
procedure SetItem(Index: Integer; const Item: TProc);
public
constructor Create;
destructor Destroy; override;
property Count: Integer read GetCount;
property Items[Index: Integer]: TProc read GetItem write SetItem; default;
function Add(const Item: TProc): Integer;
procedure Delete(Index: Integer);
procedure Clear;
end;
type
TProcListContainer = class(TList)
protected
procedure Notify(Ptr: Pointer; Action: TListNotification); override;
end;
procedure TProcListContainer.Notify(Ptr: Pointer; Action: TListNotification);
begin
inherited;
case Action of
lnDeleted:
Dispose(Ptr);
end;
end;
constructor TProcList.Create;
begin
inherited;
FList := TProcListContainer.Create;
end;
destructor TProcList.Destroy;
begin
FList.Free;
inherited;
end;
function TProcList.GetCount: Integer;
begin
Result := FList.Count;
end;
function TProcList.GetItem(Index: Integer): TProc;
begin
Result := PProc(FList[Index])^;
end;
procedure TProcList.SetItem(Index: Integer; const Item: TProc);
var
P: PProc;
begin
New(P);
P^ := Item;
FList[Index] := P;
end;
function TProcList.Add(const Item: TProc): Integer;
var
P: PProc;
begin
New(P);
P^ := Item;
Result := FList.Add(P);
end;
procedure TProcList.Delete(Index: Integer);
begin
FList.Delete(Index);
end;
procedure TProcList.Clear;
begin
FList.Clear;
end;
Disclaimer: completely untested code, use at your own risk.