Delphi XE2 之 FireMonkey 入門(24) – 資料繫結: TBindingsList: TBindExpression.Direction

在學習 BindingSource 屬性時, 可以讓兩個控制項互為繫結來源; TBindExpression 對應的功能是 Direction 屬性.

先在表單上添加 Edit1、Edit2、BindingsList1; 然後啟用 Edit1、Edit2 和表單的預設事件.

procedure TForm1.FormCreate(Sender: TObject);begin  with TBindExpression.Create(BindingsList1) do  begin    ControlComponent := Edit2;    ControlExpression := 'Text';    SourceComponent := Edit1;    SourceExpression := 'Text';//    Direction := TExpressionDirection.dirSourceToControl; //預設//    Direction := TExpressionDirection.dirControlToSource; //反向    Direction := TExpressionDirection.dirBidirectional;     //雙向    Active := True;  end;end;procedure TForm1.Edit1Change(Sender: TObject);begin  BindingsList1.Notify(Sender, '');end;procedure TForm1.Edit2Change(Sender: TObject);begin  BindingsList1.Notify(Sender, '');end;

如果沒有 Direction 屬性, 代碼或許會是:

procedure TForm1.FormCreate(Sender: TObject);begin  with TBindExpression.Create(BindingsList1) do  begin    ControlComponent := Edit2;    ControlExpression := 'Text';    SourceComponent := Edit1;    SourceExpression := 'Text';    Active := True;  end;  with TBindExpression.Create(BindingsList1) do  begin    ControlComponent := Edit1;    ControlExpression := 'Text';    SourceComponent := Edit2;    SourceExpression := 'Text';    Active := True;  end;end;procedure TForm1.Edit1Change(Sender: TObject);begin  BindingsList1.Notify(Sender, '');end;procedure TForm1.Edit2Change(Sender: TObject);begin  BindingsList1.Notify(Sender, '');end;