Custom property only trigger read statement - excel

Question

So, I'm trying to make a component that will do the job on setting the settings of a excel, libreoffice, etc... cells. At first I just wanted to set the value, but now, I need to change cell background color, change font name, style, set a formula, etc... So for that, I decided to do a type that will hold all the things I want to change and so, I did this:
type
TMyCell = class
private
FBgColor: TColor;
FValue: String;
FFormula: String;
FFormat: String;
FFont: TFont;
public
constructor Create;
destructor Destroy;
property Value: String read FValue write FValue;
property Formula: String read FFormula write FFormula;
property Format: String read FFormat write FFormat;
property BgColor: TColor read FBgColor write FBgColor;
property Font: TFont read FFont write FFont;
end;
{ TMyCell }
constructor TMyCell.Create;
begin
FFont := TFont.Create;
end;
destructor TMyCell.Destroy;
begin
FFont.Free;
end;
And my component look like this:
type
TMyPlan = class(TComponent)
private
FExcel: Variant;
procedure SetMyCell(Row, Column: Integer; Value: TMyCell);
function GetMyCell(Row, Column: Integer): TMyCell;
public
constructor Create(AOwner: TComponent);
destructor Destroy;
property Cell[Row, Column: Integer]: TMyCell read GetMyCell write SetMyCell;
end;
{ TMyPlan }
constructor TMyPlan.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
FExcel := CreateOleObject('Excel.Application');
FExcel.Workbooks.Add(1);
end;
destructor TMyPlan.Destroy;
begin
FExcel := Unassigned;
inherited;
end;
function TMyPlan.GetMyCell(Row, Column: Integer): TMyCell;
begin
Result := TMyCell.Create;
Result.Value := FExcel.Cells[Row, Column];;
end;
procedure TMyPlan.SetMyCell(Row, Column: Integer; Value: TMyCell);
begin
FExcel.Cells[Row, Column] := Value.Value;
end;
Just to let you know, I already did some components, and I'm still learning how to do them properly, so this may have a not decent structure, anyway, this is the first time that I'm trying to do something like this, a property that has input parameters with subproperties, and it doesn't seem to work as I though it would.
Back to the topic, it doesn't matter how I call my property
Set: MyPlan.Cell[1, 1].Value := '1';
Get: ShowMessage(MyPlan.Cell[1, 1].Value);
Either way only the GetMyCell function is triggered. Why's that?

Answer 1

See my answer to this question: "Left side cannot be assigned to" for record type properties in Delphi
While what you're doing isn't quite the same thing, it is similar. However, in your case, you're allocating a new instance of TMyCell for every access to GetMyCell. This "temporary" instance is isn't being freed and will leak (Unless you're doing this on one of the ARC platforms).
The reason your SetMyCell isn't being called is because you're not actually setting the cell itself, rather you're setting a value on the cell instance (that I explained above is leaking).