Best Practice: Wann verwendet ihr Exceptions in Funktionen?

[Sir Rufo]

Mit Exceptions wird zudem der Code in der Regel kompakter und übersichtlicher.

Beispiel ohne Exceptions:

Delphi-Quellcode:

procedure foo;
var
  LHandle1, LHandle2, LHandle3, LHandle4 : THandle;
begin
  LHandle1 := GetHandleFromElsewhere;
  if LHandle1 <> INVALID_HANDLE then
  begin
    LHandle2 := GetHandleFromElsewhere( LHandle1 );
    if LHandle2 <> INVALID_HANDLE then
    begin
      LHandle3 := GetHandleFromElsewhere( LHandle2 );
      if LHandle3 <> INVALID_HANDLE then
      begin
        LHandle4 := GetHandleFromElsewhere( LHandle3 );
        if LHandle4 <> INVALID_HANDLE then
        begin
          DoSomethingWithHandles( LHandle1, LHandle2, LHandle3, LHandle4 );
        end;
      end;
    end;
  end;
end;

Jetzt mal mit Exceptions

Delphi-Quellcode:

type 
  EInvalidHandleException = class( Exception );

procedure CheckInvalidHandle( AHandle : THandle; const AText : string );
begin
  if AHandle = INVALID_HANDLE then
    raise EInvalidHandleException.Create( AText );
end;

procedure foo;
var
  LHandle1, LHandle2, LHandle3, LHandle4 : THandle;
begin
  LHandle1 := GetHandleFromElseWhere;
  CheckInvalidHandle( LHandle1, 'from ElseWhere' );

  LHandle2 := GetHandleFromElseWhere( LHandle1 );
  CheckInvalidHandle( LHandle2, 'from ElseWhere' );

  LHandle3 := GetHandleFromElseWhere( LHandle2 );
  CheckInvalidHandle( LHandle3, 'from ElseWhere' );

  LHandle4 := GetHandleFromElseWhere( LHandle3 );
  CheckInvalidHandle( LHandle4, 'from ElseWhere' );

  DoSomethingWithHandles( LHandle1, LHandle2, LHandle3, LHandle4 );
end;