TClientDataSet[22]: 数组字段与 ObjectView

数组字段(ftArray) 与 ADT 字段类似(设计过程一样), 定义数组字段时只需定义一个元素来说明元素类型.

本例同时测试 ObjectView 为 True 和 False 时的不同效果.

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下面是在运行时实现的数组字段:

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//先在窗体上放置: DBGrid1、DataSource1、ClientDataSet1 并关联, 然后:

procedure TForm1.FormCreate(Sender: TObject);
begin
//  ClientDataSet1.ObjectView := True;

  { 先定义两个基本字段 }
  with ClientDataSet1.FieldDefs.AddFieldDef do begin
    Name := 'ID';
    DataType := ftInteger;
  end;
  with ClientDataSet1.FieldDefs.AddFieldDef do begin
    Name := 'Group';
    DataType := ftString;
    Size := 7;
  end;

  { 定义数组字段: 假如数组包括 4 个元素 }
  with ClientDataSet1.FieldDefs.AddFieldDef do begin
    Name := 'Member';
    DataType := ftArray;
    Size := 4;
    ChildDefs.Add('TempName', ftString, 11); { 只需定义一个子元素来说明元素类型 }
  end;
  ClientDataSet1.CreateDataSet;

  { 添加记录 }
  ClientDataSet1.AppendRecord([1, '一组', VarArrayOf(['A1','A2','A3','A4'])]);

  { 下面的添加方式也可用于访问 }
  ClientDataSet1.Append;
  ClientDataSet1['ID'] := 2;
  ClientDataSet1['Group'] := '二组';
  TArrayField(ClientDataSet1.FieldByName('Member'))[0] := 'B1';
  TArrayField(ClientDataSet1.FieldByName('Member'))[1] := 'B2';
  TArrayField(ClientDataSet1.FieldByName('Member')).FieldValues[2] := 'B3';
  TArrayField(ClientDataSet1.FieldByName('Member')).FieldValues[3] := 'B4';
  ClientDataSet1.Post;

  ClientDataSet1.Append;
  ClientDataSet1['ID'] := 3;
  ClientDataSet1['Group'] := '三组';
  TArrayField(ClientDataSet1.FieldByName('Member')).Fields[0].AsString := 'B1';
  TArrayField(ClientDataSet1.FieldByName('Member')).Fields[1].AsString := 'B2';
  TArrayField(ClientDataSet1.FieldByName('Member')).Fields[2].Value := 'B3';
  TArrayField(ClientDataSet1.FieldByName('Member')).Fields[3].Value := 'B4';
  ClientDataSet1.Post;
end;

{ 可以通过下面代码查看 ObjectView 为 True 和 False 时的不同 }
procedure TForm1.Button1Click(Sender: TObject);
begin
  ClientDataSet1.Close;
  ClientDataSet1.ObjectView := not ClientDataSet1.ObjectView;
  Text := Format('ObjectView: %s', [BoolToStr(ClientDataSet1.ObjectView, True)]);
  ClientDataSet1.Open;
end;