内存表 FDMemTable ClientDataSet CreateDataSet 动态创建字段-白红宇

内存表 FDMemTable ClientDataSet CreateDataSet 动态创建字段

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发布时间：2019-06-22

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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 = 0 ;i < ClientDataSet1->Fields->Count ;i++)   ClientDataSet1->Fields->Fields[0]->Free();//释放所有的静态字段   for(int i = 0 ;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 = 0;  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, 0, true);  cds1->FieldDefs->Add("Name", ftString, 20, false);  cds1->FieldDefs->Add("DT", ftDateTime, 0, false);  cds1->CreateDataSet();    cds1->AppendRecord(  ARRAYOFCONST((101,"aaa",Now().DateTimeString() )));  cds1->AppendRecord(  ARRAYOFCONST((102,"bbb",Now().DateTimeString() )));  cds1->AppendRecord(  ARRAYOFCONST((103,"ccc",Now().DateTimeString() )));

ClientDataSet1.Close();  ClientDataSet1.FieldDefs.Clear();  ClientDataSet1.FieldDefs.Add('ID', ftInteger, 0, true);  ClientDataSet1.FieldDefs.Add('Name', ftString, 20, false);  ClientDataSet1.FieldDefs.Add('DT', ftDateTime, 0, false);  ClientDataSet1.FieldDefs.Add('chk', ftBoolean, 0, false);  ClientDataSet1.CreateDataSet();  ClientDataSet1.Open;  ClientDataSet1.Append;  ClientDataSet1.FieldByName('id').Value := 101;  ClientDataSet1.FieldByName('name').Value := 'abc';  ClientDataSet1.FieldByName('dt').Value := Now;  ClientDataSet1.Post;  ClientDataSet1.AppendRecord([102,'bbb',Now()]);  ClientDataSet1.AppendRecord([103,'ccc',Now()]);

CreateDataSet

FDMemTable1->Close();FDMemTable1->FieldDefs->Clear();FDMemTable1->FieldDefs->Add("ID", ftInteger, 0, true);FDMemTable1->FieldDefs->Add("Name", ftString, 20, false);FDMemTable1->FieldDefs->Add("DT", ftDateTime, 0, false);FDMemTable1->CreateDataSet();FDMemTable1->AppendRecord(ARRAYOFCONST((101, "aaa", Now().DateTimeString())));FDMemTable1->AppendRecord(ARRAYOFCONST((102, "bbb", Now().DateTimeString())));FDMemTable1->AppendRecord(ARRAYOFCONST((103, "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 := 10;      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 = 10;  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 = 10;    fd = ClientDataSet1->FieldDefs->AddFieldDef();    fd->InternalCalcField = true;    fd->Name = "flag";    fd->DataType = ftBoolean;    ClientDataSet1->FieldDefs->Add("ID", ftString, 0, false);    ClientDataSet1->FieldDefs->Add("Name", ftString, 20, false);    ClientDataSet1->FieldDefs->Add("DT", ftString, 0, false);    ClientDataSet1->FieldDefs->Add("my", ftString, 0, false);    ClientDataSet1->FieldDefs->Find("my")->InternalCalcField = true;     for(int i = 0 ;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 = 0; 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