-пусть есть TreeView, соединенный с базой, скажем MySQL
-пусть мы хотим удалить выделенный узел TreeView из базы данных и из дерева
Алгоритм (пока что №1 в моем рейтинге)
-собрать ID всех детей (рекурсивно), хранящиеся по указателю каждого узла дерева SomeNode.Data
-удалить все записи с этими ID из БД
-удалить указатели всех детей в TreeView обычным обходом всех детей через repeat until
-удалить всех детей из дерева
-удалить указатель удаляемого узла
-удалить сам узел
Вот пример из одной из программ
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procedure TPSDBTreeExplorerDelete.DeleteSelectedNode3; var id:integer; Node: TtreeNode; i: Integer; TempNode:TTreeNode; begin //deleting children from db Node:=(FMainFrame as TPSDBTreeExplorerMainFrame).TreeView.Selected; if (Node=nil) or (Node.Data=nil) then Exit; id:=integer(Node.data^); SetLength(FIDArrayChildrenToDelete,0); // !!! here because of recursion GatherAllChildrenID( Integer(Node.Data^) ); for i := 0 to High(FIDArrayChildrenToDelete) do DeleteRecordFromDB(FIDArrayChildrenToDelete[i]); //Delete pointers of children TempNode:=Node; repeat Dispose(TempNode.Data); TempNode.Data:=nil; TempNode:=TempNode.GetNext; until (not Assigned(TempNode)) or (TempNode.Level=Node.Level); with (FMainFrame as TPSDBTreeExplorerMainFrame).TreeView do begin Items.BeginUpdate; Node.DeleteChildren; //deleting itself DeleteRecordFromDB(id); Dispose(Node.Data); Node.Data:=nil; Node.Delete; Items.EndUpdate; end; end; |
Алгоритм (из книги Осипова про базы данных)
Удаляет только то, что видно в дереве. Обходит дерево своеобразным способом и удаляет узлы. Это недостаток на мой взгляд. Скажем, у меня есть режим – показывать только папки, в которых содержатся файлы, но которые не отображаются. Что делать в этом случае – непонятно? Для решения этой проблемы я разработал алгоритм, который указан первым в данном посте.
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procedure TPSDBTreeExplorerDelete.DeleteSelectedNode2; var Node:TTreeNode; begin with (FMainFrame as TPSDBTreeExplorerMainFrame) do begin Node:=TreeView.Selected; if (Node=nil) or (Node.Data=nil) then Exit; while TreeView.Selected.HasChildren do begin Node:=TreeView.Selected.GetLastChild; while Node.HasChildren do Node:=Node.GetLastChild; Dispose(Node.Data); DeleteRecordFromDB(Node); //Удаляем из базы TreeView.Items.Delete(Node); // Удаляем из дерева end; //Удаляем родителя DeleteRecordFromDB(TreeView.Selected); Dispose(TreeView.Selected.Data); TreeView.Selected.Delete; end; end; |
Исходники (юнит полностью)
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unit uPSDBTreeExplorer.Delete; interface uses System.SysUtils, System.Classes,Vcl.ComCtrls; type TPSDBTreeExplorerDelete = class(TDataModule) private FMainFrame:TObject; FIDArrayChildrenToDelete:array of integer; { Private declarations } public { Public declarations } constructor Create(AOwner: TComponent); override; procedure DeleteAllChildrenFromTree(Node: TTreeNode); procedure DeleteSelectedNode; {< !!! doesn't work correctly} procedure DeleteSelectedNode2; {< from Osipov - deletes only that visible in tree, so in db may be left undeleted invisible descendents} procedure DeleteSelectedNode3; procedure ClearAllTree; procedure ClearAllChildrenFromTree(Node: TTreeNode); procedure ClearAllPointers; procedure DeleteRecordFromDB(Node:TTreeNode); overload; procedure DeleteRecordFromDB(Aid:integer); overload; procedure GatherAllChildrenID(Aid: integer); property MainFrame:TObject read FMainFrame write FMainFrame; end; var PSDBTreeExplorerDelete: TPSDBTreeExplorerDelete; implementation uses uPSDBTreeExplorer.MainFrame.ModelController, uPSDBTreeExplorer.MainFrame; var MainFrameModelController_UnitVar:TPSDBTreeExplorerMainFrameModelController; {%CLASSGROUP 'Vcl.Controls.TControl'} {$R *.dfm} constructor TPSDBTreeExplorerDelete.Create(AOwner: TComponent); begin inherited; if (AOwner is TPSDBTreeExplorerMainFrameModelController) then MainFrameModelController_UnitVar:= (AOwner as TPSDBTreeExplorerMainFrameModelController) end; procedure TPSDBTreeExplorerDelete.DeleteAllChildrenFromTree(Node:TTreeNode); var StartLevel:integer; StartNode:TTreeNode; TempNodeData:integer; idPointer:^integer; begin //Node:=PSDBTreeExplorerMainFrame_UnitVar.TreeView.Selected; if Node=nil then Exit; StartNode:=Node; if StartNode.Data<>nil then TempNodeData:=Integer(StartNode.Data^); //clear pointers repeat // begin if (Node<>nil) and (Node.Data<>nil) then begin with MainFrameModelController_UnitVar do begin //delete from db SQLQueries.SetDeleteWhereIDSQLText(Integer(Node.Data^).ToString()); SQLQueries.qDeleteWhereID.ExecSQL; end; Dispose(Node.Data); Node.Data:=nil; end; Node:=Node.GetNext; end; until (not Assigned(Node)) or (Node.Level=StartNode.Level); // delete all children from tree StartNode.DeleteChildren; // setting back pointer if StartNode.Data<>nil then begin New(idPointer); idPointer^:=(TempNodeData); StartNode.Data:=idPointer; end; end; procedure TPSDBTreeExplorerDelete.DeleteRecordFromDB(Aid: integer); begin with (FMainFrame as TPSDBTreeExplorerMainFrame) do begin // //delete from db ModelController.SQLQueries. SetDeleteWhereIDSQLText(Aid.ToString); ModelController.SQLQueries.qDeleteWhereID.ExecSQL; end; end; procedure TPSDBTreeExplorerDelete.DeleteRecordFromDB(Node: TTreeNode); begin if (Node=nil) or (Node.Data=nil) then Exit; with (FMainFrame as TPSDBTreeExplorerMainFrame) do begin // //delete from db ModelController.SQLQueries. SetDeleteWhereIDSQLText(Integer(Node.Data^).ToString()); ModelController.SQLQueries.qDeleteWhereID.ExecSQL; end; end; procedure TPSDBTreeExplorerDelete.DeleteSelectedNode; begin with (FMainFrame as TPSDBTreeExplorerMainFrame) do begin if TreeView.Selected<>nil then DeleteAllChildrenFromTree(TreeView.Selected); //clear pointer if needed and delete node if TreeView.Selected.Data<>nil then begin with MainFrameModelController_UnitVar do begin //delete from db SQLQueries.SetDeleteWhereIDSQLText(Integer(TreeView.Selected.Data^).ToString()); SQLQueries.qDeleteWhereID.ExecSQL; end; Dispose(TreeView.Selected.Data); TreeView.Selected.Data:=nil; end; TreeView.Selected.Delete; end; end; procedure TPSDBTreeExplorerDelete.DeleteSelectedNode2; var Node:TTreeNode; begin with (FMainFrame as TPSDBTreeExplorerMainFrame) do begin Node:=TreeView.Selected; if (Node=nil) or (Node.Data=nil) then Exit; while TreeView.Selected.HasChildren do begin Node:=TreeView.Selected.GetLastChild; while Node.HasChildren do Node:=Node.GetLastChild; Dispose(Node.Data); DeleteRecordFromDB(Node); //Удаляем из базы TreeView.Items.Delete(Node); // Удаляем из дерева end; //Удаляем родителя DeleteRecordFromDB(TreeView.Selected); Dispose(TreeView.Selected.Data); TreeView.Selected.Delete; end; end; procedure TPSDBTreeExplorerDelete.DeleteSelectedNode3; var id:integer; Node: TtreeNode; i: Integer; TempNode:TTreeNode; begin //deleting children from db Node:=(FMainFrame as TPSDBTreeExplorerMainFrame).TreeView.Selected; if (Node=nil) or (Node.Data=nil) then Exit; id:=integer(Node.data^); SetLength(FIDArrayChildrenToDelete,0); // !!! here because of recursion GatherAllChildrenID( Integer(Node.Data^) ); for i := 0 to High(FIDArrayChildrenToDelete) do DeleteRecordFromDB(FIDArrayChildrenToDelete[i]); //Delete pointers of children TempNode:=Node; repeat Dispose(TempNode.Data); TempNode.Data:=nil; TempNode:=TempNode.GetNext; until (not Assigned(TempNode)) or (TempNode.Level=Node.Level); with (FMainFrame as TPSDBTreeExplorerMainFrame).TreeView do begin Items.BeginUpdate; Node.DeleteChildren; //deleting itself DeleteRecordFromDB(id); Dispose(Node.Data); Node.Data:=nil; Node.Delete; Items.EndUpdate; end; end; procedure TPSDBTreeExplorerDelete.GatherAllChildrenID(Aid: integer); var LocalIDArray:array of integer; i: Integer; begin //select all children from db (FMainFrame as TPSDBTreeExplorerMainFrame).ModelController. SQLQueries.SetSelectAllChildrenSQLText(Aid.ToString,'0'); //gather their id with (FMainFrame as TPSDBTreeExplorerMainFrame).ModelController. SQLQueries.qSelectAllChildren do begin Open(); SetLength(LocalIDArray,0); while not EOF do begin // adding final array SetLength(FIDArrayChildrenToDelete,Length(FIDArrayChildrenToDelete)+1); FIDArrayChildrenToDelete[Length(FIDArrayChildrenToDelete)-1]:=FieldByName('id').AsInteger; //LocalIDArray SetLength(LocalIDArray,Length(LocalIDArray)+1); LocalIDArray[Length(LocalIDArray)-1]:=FieldByName('id').AsInteger; Next(); end; Close(); end; //call recursievely itself for i := 0 to High(LocalIDArray) do begin GatherAllChildrenID(LocalIDArray[i]); end; end; procedure TPSDBTreeExplorerDelete.ClearAllTree(); var TempNodeData:integer; idPointer:^integer; Node:TTreeNode; begin Node:=(FMainFrame as TPSDBTreeExplorerMainFrame).TreeView.Items.GetFirstNode; if Node=nil then Exit; //clear pointers repeat // begin if (Node<>nil) and (Node.Data<>nil) then begin Dispose(Node.Data); Node.Data:=nil; end; Node:=Node.GetNext; end; until (not Assigned(Node)); (FMainFrame as TPSDBTreeExplorerMainFrame).TreeView.Items.Clear; end; procedure TPSDBTreeExplorerDelete.ClearAllChildrenFromTree(Node:TTreeNode); var StartLevel:integer; StartNode:TTreeNode; TempNodeData:integer; idPointer:^integer; begin //Node:=PSDBTreeExplorerMainFrame_UnitVar.TreeView.Selected; if Node=nil then Exit; StartNode:=Node; TempNodeData:=Integer(StartNode.Data^); //clear pointers repeat // begin if (Node<>nil) and (Node.Data<>nil) then begin Dispose(Node.Data); Node.Data:=nil; end; Node:=Node.GetNext; end; until (not Assigned(Node)) or (Node.Level=StartNode.Level); // delete all children from tree StartNode.DeleteChildren; // setting back pointer New(idPointer); idPointer^:=(TempNodeData); StartNode.Data:=idPointer; end; procedure TPSDBTreeExplorerDelete.ClearAllPointers; var Node:TTreeNode; begin with (FMainFrame as TPSDBTreeExplorerMainFrame) do begin Node:=TreeView.Items.GetFirstNode; if Node=nil then Exit; repeat // DoSomething with Tree for Example // Node.Text:='Was here during travesing'; Dispose(Node.Data); Node:=Node.GetNext; until not Assigned(Node) ; end; end; end. |