This is what I have:

In a unit where a logging class is defined:

type
  TRxEvent = procedure (const Buffer: TBytes) of object;
...
  TWiFiCommLogger = class(TThread)
  private
  ...
    FOnRxData: TRxEvent;
  ...
  public
  ...
    property OnRxData: TRxEvent read FOnRxData write FOnRxData;
  ...
end;
procedure TWiFiCommLogger.Execute;
begin
  while not Terminated do
  begin
     ...
      if Assigned(FOnRxData) then
      begin
        FOnRxData(FBuffer);
        SetLength(FBuffer, 0);
      end;
     ...

Then in the form unit where I want to use this:
...

  private

...

    procedure OnRxSS(Buf: TBytes);

...
end;

In the form constructor:

procedure TfrmCommTest.FormCreate(Sender: TObject);
...
  FLogSS := TWiFiCommLogger.Create;
  FLogSS.OnRxData := OnRxSS;  // <== Error on this line
...

When I compile this I get the following error:

formcommtest.pas(112,22) Error: Incompatible types: got "TfrmCommTest.OnRxSS(TBytes);" expected "<procedure variable type of procedure(const TBytes) of object;Register>"

What am I doing wrong here?

I have written similar types of programs where I have used this kind of construction and it has worked fine (in Delphi).

Both the form file and the unit where the handler class is defined have been set to:

{$mode Delphi}

Missing "const" before Buf?

procedure OnRxSS(*const* Buf: TBytes);

W dniu 2018-10-13 o 20:43, Bo Berglund via Lazarus pisze:

Regards, Michał.

Did you try simply to add "const"?
 
V.
______________________________________________________________

What am I doing wrong here?

I have written similar types of programs where I have used this kind of construction and it has worked fine (in Delphi).

Both the form file and the unit where the handler class is defined have been set to:

 {$mode Delphi}

Bo Berglund wrote

type TRxEvent = procedure (const Buffer: TBytes) of object;

Of course posting here is the best way to actually discover the solution just a few minutes afterwards...

The const specifier was missing in the implementation on the form where I wanted to use the class object. Adding it in let the compile succeed!

Sorry for the noise.

Bo Berglund wrote

Sorry for the noise.

This is just a test of posting via GMane since my posts on the fpc list have been rejected. Reason unknown to me. Worked for years until now...

After rebooting my router, thus obtaining a different Internet IP address my rejection from the fpc.general list disappeared. Surely a GMane thing...