我试图在运行时在窗体中定义ClientDataSet组件.我可以成功定义所有字段并在VCL表单程序中操作ClientDataSet,但是当我尝试将诸如AfterInsert之类的事件的事件处理程序添加到代码中时,编译器会对应于我的格式.
clientDataset在此过程中创建:
procedure TForm1.CreatenestedDataSets; begin cdsTables := TClientDataSet.Create(Self); cdsNotes := TClientDataSet.Create(cdsTables); //nested dataset //Define Tables with TFloatField.Create(Self) do begin Name := 'TblID'; FieldKind := fkData; FieldName := 'ID'; DataSet := cdsTables; required := True; end; ... //define other fields for cdsTables & nested clientdataset cdsNotes cdsNotes.AfterInsert := cdsNotesAfterInsert(cdsNotes: TDataSet); //Create the ClientDataSet and its nested datasets cdsTables.CreateDataSet; //This is problem code line: cdsNotes.AfterInsert := cdsNotesAfterInsert; //Configure the DataSources dsTables.DataSet := cdsTables; dsNotes.DataSet := cdsNotes; end;
各种论坛讨论都提出了这个例子的方法:
MyLabel := TLabel.Create(self); MyLabel.OnClick := MyLabelClick;
在AfterInsert的情况下,包含一个参数.如果我在设计时生成事件,Delphi会生成:
procedure TForm1.ClientDataSet1AfterInsert(DataSet: TDataSet);
cdsNotes.AfterInsert:= cdsNotesAfterInsert;不兼容的类型参数列表不同
其他格式也会产生错误:
cdsNotes.AfterInsert:= cdsNotesAfterInsert(DataSet:TDataSet);实际参数太多
我已尝试其他变种与错误消息的assorment.这是我第一次尝试定义一个事件,我不确定我是否理解如何处理该声明.我相信我声明实现事件的实际过程’cdsNotesAfterInsert’不需要任何参数,因为它是绑定的
到clientdataset cdsNotes.如果我错了,请纠正我.
unit ForumTest; interface uses Winapi.Windows,Winapi.Messages,System.SysUtils,System.Variants,System.Classes,Vcl.Graphics,Vcl.Controls,Vcl.Forms,Vcl.Dialogs,Data.DB,DBClient; type TForm1 = class(TForm) procedure FormCreate(Sender: TObject); private { Private declarations } public { Public declarations } cdsTables : tclientDataset; cdsNotes :tclientDataset; procedure CreatenestedDataSets; end; var Form1: TForm1; implementation {$R *.dfm} procedure TForm1.CreatenestedDataSets; begin cdsTables := TClientDataSet.Create(Self); cdsNotes := TClientDataSet.Create(cdsTables); //Define Tables with TFloatField.Create(Self) do begin Name := 'TblID'; FieldKind := fkData; FieldName := 'ID'; DataSet := cdsTables; required := True; end; with TFloatField.Create(Self) do begin Name := 'TblParentID'; FieldKind := fkData; FieldName := 'Parent'; DataSet := cdsTables; required := false; end; with TStringField.Create(Self) do begin Name := 'TblTitle'; FieldKind := fkData; FieldName := 'Title'; Size := 40; DataSet := cdsTables; required := True; end; with TStringField.Create(Self) do begin Name := 'TblFilename'; FieldKind := fkData; FieldName := 'Filename'; Size := 80; DataSet := cdsTables; required := False; end; //Note: For TDataSetFields,FieldKind is fkDataSet by default with TDataSetField.Create(Self) do begin Name := 'TblNotes'; FieldName := 'nestedDataSet'; DataSet := cdsTables; end; //Define Notes cdsNotes.DataSetField := TDataSetField(FindComponent('TblNotes')); with TFloatField.Create(Self) do begin Name := 'NoteID'; FieldKind := fkData; FieldName := 'Note ID'; DataSet := cdsNotes; required := True; end; with TStringField.Create(Self) do begin Name := 'NoteTxt'; FieldKind := fkData; FieldName := 'Notes'; DataSet := cdsNotes; Size := 40; end; cdsNotes.AfterInsert := cdsNotesAfterInsert(cdsNotes: TDataSet); //Create the ClientDataSet and its nested datasets cdsTables.CreateDataSet; //Configure the DataSources dsTables.DataSet := cdsTables; dsNotes.DataSet := cdsNotes; end; procedure TForm1.FormCreate(Sender: TObject); begin CreatenestedDataSets; end; end.
解决方法
这是专门回答您关于如何将一些自编代码分配给TClientDataSet的AfterInsert事件属性的观点.
如果在在线帮助中查找TClientDataSet.AfterInsert,您将看到它被定义为TDataSetNotifyEvent,而后者又被定义为
type TDataSetNotifyEvent = procedure(DataSet: TDataSet) of object
对象的意义在于,过程必须是对象的方法(对于其读取“类”),而不是您在评论中描述的独立过程/方法.
要与TDataSetNotifyEvent分配兼容,您的过程需要具有匹配的代码“signature”,也就是说,它必须是类的过程(不是类的函数)并且具有完全相同的参数,在这种情况下单个TDataSet参数.
所以你需要的就是这样
type TForm1 = class(TForm) ClientDataSet1: TClientDataSet; procedure FormCreate(Sender: TObject); protected procedure MyInsertHandler(ADataSet : TDataSet); end; [...] procedure TForm1.FormCreate(Sender: TObject); begin ClientDataSet1.AfterInsert := MyInsertHandler; end; procedure TForm1.MyInsertHandler(ADataSet: TDataSet); begin // Your code goes here,e.g. Caption := ADataSet.Name + ' after insert'; end;
就那么简单.