内存表 FDMemTable ClientDataSet CreateDataSet 动态创建字段

2023-07-22 19:30:16

https://community.embarcadero.com/index.php/blogs/entry/firedac-in-memory-dataset-tfdmemtable

ClientDataSet FieldDefs Add Field CreateDataSet 动态创建字段

  FDMemTable1.Close();

  FDMemTable1.FieldDefs.Clear();

  FDMemTable1.FieldDefs.Add('ID', ftInteger, 0, True);

  FDMemTable1.FieldDefs.Add('Name', ftString, 20, false);

  FDMemTable1.CreateDataSet();

  FDMemTable1.AppendRecord([101, 'aaa']);

  FDMemTable1.AppendRecord([102, 'bbb']);

  FDMemTable1.AppendRecord([103, 'ccc']);

　　TFDMemTable *table= new TFDMemTable();

delete table;

void __fastcall TForm1::createField()

{

  ClientDataSet1->Close();

  ClientDataSet1->Fields->Clear();

  ClientDataSet1->FieldDefs->Clear();

  ClientDataSet1->Open();

  ClientDataSet1->Close();

  for(int i =  ;i < ClientDataSet1->Fields->Count ;i++)

   ClientDataSet1->Fields->Fields[]->Free();//释放所有的静态字段

  for(int i =  ;i < ClientDataSet1->FieldDefs->Count ;i++)

    ClientDataSet1->FieldDefs->Items[i]->CreateField(ClientDataSet1);

  TBooleanField *NewField;

  NewField = new TBooleanField(ClientDataSet1);

  NewField->FieldName="SelectMe";

  NewField->DisplayLabel = "选择";

  NewField->FieldKind=fkInternalCalc;

  NewField->DataSet=ClientDataSet1;

  NewField->Index = ;

  ClientDataSet1->Open();

}
void __fastcall TForm1::BitBtn1Click(TObject *Sender)
{
        sql = "select  from TABLE1 ";
        this->ADOQuery1->Close();
        this->ADOQuery1->SQL->Clear();
        this->ADOQuery1->SQL->Add(this->sql);
        this->ADOQuery1->Open();
        this->createField();
}

  cds1->Close();

  cds1->FieldDefs->Clear();

  cds1->FieldDefs->Add("ID", ftInteger, , true);

  cds1->FieldDefs->Add("Name", ftString, , false);

  cds1->FieldDefs->Add("DT", ftDateTime, , false);

  cds1->CreateDataSet();

  cds1->AppendRecord(  ARRAYOFCONST((,"aaa",Now().DateTimeString() )));

  cds1->AppendRecord(  ARRAYOFCONST((,"bbb",Now().DateTimeString() )));

  cds1->AppendRecord(  ARRAYOFCONST((,"ccc",Now().DateTimeString() )));

  ClientDataSet1.Close();

  ClientDataSet1.FieldDefs.Clear();

  ClientDataSet1.FieldDefs.Add('ID', ftInteger, , true);

  ClientDataSet1.FieldDefs.Add('Name', ftString, , false);

  ClientDataSet1.FieldDefs.Add('DT', ftDateTime, , false);

  ClientDataSet1.FieldDefs.Add('chk', ftBoolean, , false);

  ClientDataSet1.CreateDataSet();

  ClientDataSet1.Open;

  ClientDataSet1.Append;

  ClientDataSet1.FieldByName('id').Value := ;

  ClientDataSet1.FieldByName('name').Value := 'abc';

  ClientDataSet1.FieldByName('dt').Value := Now;

  ClientDataSet1.Post;

  ClientDataSet1.AppendRecord([,'bbb',Now()]);

  ClientDataSet1.AppendRecord([,'ccc',Now()]);

CreateDataSet

FDMemTable1->Close();

FDMemTable1->FieldDefs->Clear();

FDMemTable1->FieldDefs->Add("ID", ftInteger, , true);

FDMemTable1->FieldDefs->Add("Name", ftString, , false);

FDMemTable1->FieldDefs->Add("DT", ftDateTime, , false);

FDMemTable1->CreateDataSet();

FDMemTable1->AppendRecord(ARRAYOFCONST((, "aaa", Now().DateTimeString())));

FDMemTable1->AppendRecord(ARRAYOFCONST((, "bbb", Now().DateTimeString())));

FDMemTable1->AppendRecord(ARRAYOFCONST((, "ccc", Now().DateTimeString())));

FDMemTable1->First();

AddFieldDef

with CDS2 do

  begin

    with FieldDefs.AddFieldDef do

    begin

      DataType := ftInteger;

      Name := 'Field1';

    end;

    with FieldDefs.AddFieldDef do

    begin

      DataType := ftString;

      Size := ;

      Name := 'Field2';

    end;

    with IndexDefs.AddIndexDef do

    begin

      Fields := 'Field1';

      Name := 'IntIndex';

    end;

    CreateDataSet;

C++也可以这样写

TVarRec row[] = {user, password, purview, "", 0};
int value_size =8;

qry->AppendRecord(row, value_size);

__fastcall TForm1::TForm1(TComponent* Owner)

    : TForm(Owner)

{

  TFieldDefs *pDefs = CDS2->FieldDefs;

  TFieldDef *pDef = pDefs->AddFieldDef();

  pDef->DataType = ftInteger;

  pDef->Name = "Field1";

  pDef = pDefs->AddFieldDef();

  pDef->DataType = ftString;

  pDef->Size = ;

  pDef->Name = "Field2";

  TIndexDef *pIDef = CDS2->IndexDefs->AddIndexDef();

  pIDef->Fields = "Field1";

  pIDef->Name = "IntIndex";

  CDS2->CreateDataSet();

}

2016.8.25 FDMemTable 试验成功，三种创建的方式都最终成了InternalCalcField字段。

ClientDataSet1->Close();

    ClientDataSet1->Fields->Clear();

    ClientDataSet1->FieldDefs->Clear();

    TFieldDef *fd;

    fd = ClientDataSet1->FieldDefs->AddFieldDef();

    fd->InternalCalcField = true;

    fd->Name = "calc1";

    fd->DataType = ftString;

    fd->Size = ;

    fd = ClientDataSet1->FieldDefs->AddFieldDef();

    fd->InternalCalcField = true;

    fd->Name = "flag";

    fd->DataType = ftBoolean;

    ClientDataSet1->FieldDefs->Add("ID", ftString, , false);

    ClientDataSet1->FieldDefs->Add("Name", ftString, , false);

    ClientDataSet1->FieldDefs->Add("DT", ftString, , false);

    ClientDataSet1->FieldDefs->Add("my", ftString, , false);

    ClientDataSet1->FieldDefs->Find("my")->InternalCalcField = true;

     for(int i =  ;i < ClientDataSet1->FieldDefs->Count ;i++)

    ClientDataSet1->FieldDefs->Items[i]->CreateField(ClientDataSet1);

      TBooleanField *NewField;

  NewField = new TBooleanField(ClientDataSet1);

  NewField->FieldName="SelectMe";

  NewField->DisplayLabel = "选择";

  NewField->FieldKind=fkInternalCalc;

  NewField->DataSet=ClientDataSet1;

//    ClientDataSet1->CreateDataSet(); 有了上面的CreateField，此句可不要。仅此句还不能创建fkInternalCalc字段，创建变成了fkData

    ClientDataSet1->Open();

    for (int i = ; i < ClientDataSet1->Fields->Count; i++)

    {

        ClientDataSet1->Fields->Fields[i]->FieldName;

        ClientDataSet1->Fields->Fields[i]->FieldKind;

    }

如果dfm窗体文件定义了字段，那么不用createDataSet了，只要open就可以了。

object ds1: TFDMemTable
    OnCalcFields = ds1CalcFields
    FieldDefs = <>
    CachedUpdates = True
    IndexDefs = <>
    FetchOptions.AssignedValues = [evMode]
    FetchOptions.Mode = fmAll
    ResourceOptions.AssignedValues = [rvSilentMode]
    ResourceOptions.SilentMode = True
    UpdateOptions.AssignedValues = [uvCheckRequired, uvAutoCommitUpdates]
    UpdateOptions.CheckRequired = False
    UpdateOptions.AutoCommitUpdates = True
    StoreDefs = True
    Left = 352
    Top = 160
    object ds1Field: TDateTimeField
      FieldName = aaa
    end
    object ds1Field2: TStringField
      FieldName = bbb
    end
    object ds1Field3: TStringField
      FieldName = ccc
    end

ds1->Close();

ds1->Open();

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