UPD: Don't need to initialize to zero class objects member variables because they are guaranteed to be zeroed in InitInstance (including static arrays and ref. counted strings).

UPD: Don't need to check if a pointer is assigned before calling Free, because Free already checks for nil pointer.

src/newdesign/ucolumnsfileview.pas

@@ -2271,18 +2271,11 @@ procedure TColumnsFileView.CreateDefault(AOwner: TWinControl);
 begin
   DCDebug('TColumnsFileView.Create components');
 
-  dgPanel := nil;
-
   BorderStyle := bsNone; // Before Create or the window handle may be recreated
   inherited CreateDefault(AOwner);
   Align := alClient;
 
-  ActiveColm := '';
-  ActiveColmSlave := nil;
-  isSlave := False;
-  FColumnsSorting := nil;
   FLastSelectionStartRow := -1;
-  FUpdatingGrid := False;
   FFileNameColumn := -1;
   FExtensionColumn := -1;
 
@@ -2388,8 +2381,9 @@ begin
   if Assigned(HotMan) then
     HotMan.UnRegister(dgPanel);
 
-  FreeThenNil(FColumnsSorting);
   inherited Destroy;
+
+  FColumnsSorting.Free;
 end;
 
 function TColumnsFileView.Clone(NewParent: TWinControl): TColumnsFileView;
@@ -2564,8 +2558,7 @@ begin
       end;
 
     finally
-      if Assigned(AFileList) then
-        FreeAndNil(AFileList);
+      FreeAndNil(AFileList);
     end;
   end;
 end;
@@ -2735,8 +2728,7 @@ begin
     CalculateSpace(AFileList);
 
   finally
-    if Assigned(AFileList) then
-      FreeAndNil(AFileList);
+    FreeAndNil(AFileList);
   end;
 end;
 
@@ -2757,8 +2749,7 @@ begin
     CalculateSpace(AFileList);
 
   finally
-    if Assigned(AFileList) then
-      FreeAndNil(AFileList);
+    FreeAndNil(AFileList);
   end;
 end;
 
@@ -2833,8 +2824,7 @@ begin
     frmMain.DoDragDropOperation(Operation, DropParams);
 
   finally
-    if Assigned(DropParams) then
-      FreeAndNil(DropParams);
+    FreeAndNil(DropParams);
   end;
 end;
 
@@ -3166,10 +3156,8 @@ end;
 
 procedure TDrawGridEx.FinalizeWnd;
 begin
-  if Assigned(DragDropSource) then
-    FreeAndNil(DragDropSource);
-  if Assigned(DragDropTarget) then
-    FreeAndNil(DragDropTarget);
+  FreeAndNil(DragDropSource);
+  FreeAndNil(DragDropTarget);
 
   inherited;
 end;

src/newdesign/udisplayfile.pas

@@ -105,7 +105,6 @@ implementation
 
 constructor TDisplayFile.Create(ReferenceFile: TFile);
 begin
-  FSelected := False;
   FIconID := -1;
   FIconOverlayID := -1;
   FFSFile := ReferenceFile;

src/newdesign/ufile.pas

@@ -279,10 +279,6 @@ var
 begin
   inherited Create;
 
-  FSupportedProperties := [];
-  for PropertyType := Low(TFilePropertyType) to High(TFilePropertyType) do
-    FProperties[PropertyType] := nil;
-
   // Name property always present.
   NameProperty := TFileNameProperty.Create;
 
@@ -853,8 +849,7 @@ var
 begin
   inherited Destroy;
 
-  if Assigned(FFile) then
-    FreeAndNil(FFile);
+  FreeAndNil(FFile);
 
   if Assigned(FSubNodes) then
   begin
@@ -863,8 +858,7 @@ begin
     FreeAndNil(FSubNodes);
   end;
 
-  if Assigned(FData) then
-    FreeAndNil(FData);
+  FreeAndNil(FData);
 end;
 
 function TFileTreeNode.AddSubNode(aFile: TFile): Integer;

src/newdesign/ufilesource.pas

@@ -365,8 +365,6 @@ begin
   inherited Create;
 
   FReloadEventListeners := TMethodList.Create;
-  for OperationType := Low(OperationType) to High(OperationType) do
-    FOperationsClasses[OperationType] := nil;
 
   FileSourceManager.Add(Self); // Increases RefCount
 
@@ -413,7 +411,7 @@ begin
   else
     DCDebug('Error: Cannot remove file source - manager already destroyed!');
 
-  FreeThenNil(FReloadEventListeners);
+  FreeAndNil(FReloadEventListeners);
 
   inherited Destroy;
 end;
@@ -763,7 +761,6 @@ end;
 
 constructor TFileSourceConnection.Create;
 begin
-  FAssignedOperation := nil;
   FOperationLock := TCriticalSection.Create;
   inherited Create;
   DCDebug('Creating connection ', ClassName);
@@ -778,8 +775,7 @@ begin
 
   DCDebug('Destroying connection ', ClassName);
 
-  if Assigned(FOperationLock) then
-    FreeAndNil(FOperationLock);
+  FreeAndNil(FOperationLock);
 end;
 
 function TFileSourceConnection.GetAssignedOperation: TFileSourceOperation;
@@ -872,10 +868,9 @@ begin
     end;
   end;
 
-  if Assigned(FFileSources) then
-    FreeAndNil(FFileSources);
+  FreeAndNil(FFileSources);
 
-  inherited;
+  inherited Destroy;
 end;
 
 procedure TFileSourceManager.Add(aFileSource: IFileSource);

src/newdesign/ufilesourceoperation.pas

@@ -425,19 +425,12 @@ begin
   FState := fsosNotStarted;
   FDesiredState := fsosRunning;  // set for auto-start unless prevented by PreventStart
   FOperationResult := fsorFinished;
-  FProgress := 0;
   FPauseEvent := RTLEventCreate;
   FConnectionAvailableEvent := RTLEventCreate;
   FStateLock := TCriticalSection.Create;
   FEventsLock := TCriticalSection.Create;
-  FThread := nil;
-  FConnection := nil;
-  FOperationInitialized := False;
-  FParentOperation := nil;
 
 {$IFNDEF fsoSynchronizeEvents}
-  FScheduledEventsListenersCalls := 0;
-
   FNoEventsListenersCallsScheduledEvent := RTLEventCreate;
   // Set at start because we don't have any calls scheduled at this time.
   RTLeventSetEvent(FNoEventsListenersCallsScheduledEvent);
@@ -450,8 +443,6 @@ begin
 
   FStateChangedEventListeners := TFPList.Create;
 
-  FStartTime := 0;
-
   FFileSource := aFileSource;
 
   FNeedsConnection := (fspUsesConnections in (FileSource as IFileSource).Properties);

src/newdesign/ufilesystemcopyoperation.pas

@@ -95,9 +95,6 @@ constructor TFileSystemCopyOperation.Create(aSourceFileSource: IFileSource;
                                             var theSourceFiles: TFiles;
                                             aTargetPath: String);
 begin
-  FSourceFilesTree := nil;
-  FOperationHelper := nil;
-
   // Here we can read global settings if there are any.
   FDropReadOnlyAttribute := False;
   FSymLinkOption := gOperationOptionSymLinks;
@@ -114,12 +111,8 @@ end;
 destructor TFileSystemCopyOperation.Destroy;
 begin
   inherited Destroy;
-
-  if Assigned(FSourceFilesTree) then
-    FreeAndNil(FSourceFilesTree);
-
-  if Assigned(FOperationHelper) then
-    FreeAndNil(FOperationHelper);
+  FreeAndNil(FSourceFilesTree);
+  FreeAndNil(FOperationHelper);
 end;
 
 procedure TFileSystemCopyOperation.Initialize;
@@ -176,8 +169,7 @@ end;
 
 procedure TFileSystemCopyOperation.Finalize;
 begin
-  if Assigned(FOperationHelper) then
-    FreeAndNil(FOperationHelper);
+  FreeAndNil(FOperationHelper);
 end;
 
 class function TFileSystemCopyOperation.GetOptionsUIClass: TFileSourceOperationOptionsUIClass;

src/newdesign/ufilesystemdeleteoperation.pas

@@ -69,12 +69,9 @@ begin
   FRecycle := False;
   FDeleteReadOnly := fsoogNone;
   FDeleteDirectly:= fsoogNone;
-  FFullFilesTreeToDelete := nil;
 
   if gProcessComments then
-    FDescription := TDescription.Create(True)
-  else
-    FDescription := nil;
+    FDescription := TDescription.Create(True);
 
   inherited Create(aTargetFileSource, theFilesToDelete);
 end;
@@ -91,8 +88,7 @@ begin
 
   if not FRecycle then
   begin
-    if Assigned(FFullFilesTreeToDelete) then
-      FreeAndNil(FFullFilesTreeToDelete);
+    FreeAndNil(FFullFilesTreeToDelete);
   end;
 end;
 

src/newdesign/ufilesystemfilesource.pas

@@ -147,9 +147,6 @@ begin
   with AFile do
   begin
     OwnerProperty := TFileOwnerProperty.Create;
-    OwnerProperty.Owner := 0;
-    OwnerProperty.Group := 0;
-
     if GetFileOwner(FullPath, sUser, sGroup) then
     begin
       OwnerProperty.OwnerStr := sUser;
@@ -285,9 +282,8 @@ end;
 
 destructor TFileSystemFileSource.Destroy;
 begin
-  if Assigned(FDescr) then
-    FreeAndNil(FDescr);
   inherited Destroy;
+  FDescr.Free;
 end;
 
 class function TFileSystemFileSource.CreateFile(const APath: String): TFile;

src/newdesign/ufilesystemmoveoperation.pas

@@ -59,9 +59,6 @@ constructor TFileSystemMoveOperation.Create(aFileSource: IFileSource;
                                             var theSourceFiles: TFiles;
                                             aTargetPath: String);
 begin
-  FSourceFilesTree := nil;
-  FOperationHelper := nil;
-
   // Here we can read global settings if there are any.
   FFileExistsOption := gOperationOptionFileExists;
   FDirExistsOption := gOperationOptionDirectoryExists;
@@ -75,12 +72,8 @@ end;
 destructor TFileSystemMoveOperation.Destroy;
 begin
   inherited Destroy;
-
-  if Assigned(FSourceFilesTree) then
-    FreeAndNil(FSourceFilesTree);
-
-  if Assigned(FOperationHelper) then
-    FreeAndNil(FOperationHelper);
+  FreeAndNil(FSourceFilesTree);
+  FreeAndNil(FOperationHelper);
 end;
 
 procedure TFileSystemMoveOperation.Initialize;

src/newdesign/ufilesystemutil.pas

@@ -27,8 +27,6 @@ type
   public
     // True if any of the subnodes (recursively) are links.
     SubnodesHaveLinks: Boolean;
-
-    constructor Create;
   end;
 
   TUpdateStatisticsFunction = procedure(var NewStatistics: TFileSourceCopyOperationStatistics) of object;
@@ -313,21 +311,12 @@ end;
 
 // ----------------------------------------------------------------------------
 
-constructor TFileTreeNodeData.Create;
-begin
-  SubnodesHaveLinks := False;
-end;
-
-// ----------------------------------------------------------------------------
-
 constructor TFileSystemTreeBuilder.Create(AskQuestionFunction: TAskQuestionFunction;
                                           CheckOperationStateFunction: TCheckOperationStateFunction);
 begin
   AskQuestion := AskQuestionFunction;
   CheckOperationState := CheckOperationStateFunction;
 
-  FFilesTree := nil;
-  FExcludeRootDir := False;
   FRecursive := True;
   FSymlinkOption := fsooslNone;
 end;
@@ -335,17 +324,14 @@ end;
 destructor TFileSystemTreeBuilder.Destroy;
 begin
   inherited Destroy;
-
-  if Assigned(FFilesTree) then
-    FreeAndNil(FFilesTree);
+  FFilesTree.Free;
 end;
 
 procedure TFileSystemTreeBuilder.BuildFromFiles(Files: TFiles);
 var
   i: Integer;
 begin
-  if Assigned(FFilesTree) then
-    FreeAndNil(FFilesTree);
+  FreeAndNil(FFilesTree);
 
   FFilesTree := TFileTreeNode.Create;
   FFilesTree.Data := TFileTreeNodeData.Create;
@@ -841,8 +827,7 @@ begin
       end;
 
     finally
-      if Assigned(SourceFileStream) then
-        FreeAndNil(SourceFileStream);
+      FreeAndNil(SourceFileStream);
       if Assigned(TargetFileStream) then
       begin
         FreeAndNil(TargetFileStream);

src/newdesign/ufileview.pas

@@ -445,36 +445,16 @@ end;
 
 procedure TFileView.CreateDefault(AOwner: TWinControl);
 begin
-  FOnBeforeChangePath := nil;
-  FOnAfterChangePath := nil;
-  FOnChangeActiveFile := nil;
-  FOnActivate := nil;
-  FOnReload := nil;
-  FSortings := nil;
-  FFilePropertiesNeeded := [];
   FMethods := TFormCommands.Create(Self);
   FHistory := TFileViewHistory.Create;
   FSavedSelection:= TStringListEx.Create;
-  FActive := False;
-  FLastActiveFile := '';
-  FRequestedActiveFile := '';
   FLastMark := '*';
-  FFileFilter := '';
   FFilterOptions := gQuickSearchOptions;
-  FFiles := nil;
-  FHashedFiles := nil;
   FHashedNames := TStringHashList.Create(True);
-  FWorkersThread := nil;
-  FReloading := False;
-  FReloadNeeded := False;
   FFileViewWorkers := TFileViewWorkers.Create(False);
-  FWatchPath := EmptyStr;
   FReloadTimer := TTimer.Create(Self);
   FReloadTimer.Enabled := False;
   FReloadTimer.OnTimer := @ReloadTimerEvent;
-  FLoadFilesStartTime := 0;
-  FLoadFilesFinishTime := 0;
-  FLoadFilesNoDelayCount := 0;
 
   inherited Create(AOwner);
   Parent := AOwner;
@@ -522,11 +502,9 @@ begin
 
   RemoveAllFileSources;
 
-  if Assigned(FFiles) then
-    FreeAndNil(FFiles);
+  FreeAndNil(FFiles);
   FreeAndNil(FAllDisplayFiles);
-  if Assigned(FHashedFiles) then
-    FreeAndNil(FHashedFiles);
+  FreeAndNil(FHashedFiles);
   FreeAndNil(FHashedNames);
 
   inherited Destroy;
@@ -955,8 +933,7 @@ var
   i: Integer;
 begin
   // Cannot use FHashedFiles.Clear because it also destroys the buckets.
-  if Assigned(FHashedFiles) then
-    FHashedFiles.Free;
+  FHashedFiles.Free;
   // TBucketList seems to do fairly well without needing a proper hash table.
   FHashedFiles := TBucketList.Create(bl256);
   FHashedNames.Clear;
@@ -1788,8 +1765,8 @@ end;
 
 destructor TDropParams.Destroy;
 begin
-  if Assigned(Files) then
-    FreeAndNil(Files);
+  inherited Destroy;
+  FreeAndNil(Files);
 end;
 
 function TDropParams.GetDragDropType: TDragDropType;

src/newdesign/ufileviewworker.pas

@@ -26,6 +26,7 @@ type
   TFileViewWorker = class
   strict private
     FAborted: Boolean;
+    {en After FCanBeDestroyed is set to True the worker may be destroyed.}
     FCanBeDestroyed: Boolean;
     FWorking: Boolean;
     FOnStarting: TStartingWorkMethod;
@@ -260,17 +261,11 @@ end;
 
 constructor TFileViewWorker.Create(AThread: TThread);
 begin
-  FAborted := False;
-  // After FCanBeDestroyed is set to True the worker may be destroyed.
-  FCanBeDestroyed := False;
-
   // Set Working=True on creation because these workers are usually scheduled
   // to run by a non-main thread, so it might take a while for Execute to be called.
   FWorking := True;
   FWorkType := fvwtNone;
 
-  FOnStarting := nil;
-  FOnFinished := nil;
   FThread := AThread;
 end;
 
@@ -872,12 +867,10 @@ begin
           end;
 
         finally
-          if Assigned(TargetFiles) then
-            FreeAndNil(TargetFiles);
+          FreeAndNil(TargetFiles);
           FOperationLock.Acquire;
           try
-            if Assigned(FOperation) then
-              FreeAndNil(FOperation);
+            FreeAndNil(FOperation);
           finally
             FOperationLock.Release;
           end;