Error SQL property custom DB Engine

dagarik

I've write a custom DB engine component. I can install it and the FrxReport object recognize it and I can use it inside DATA PAGE. I can set the sql property using or not params and it gets fields perfectly.

The problem is when I put the second custom query component, because it always gets the SQL property value from the last one component, I mean, when I put the third component, it gets SQL property value from the second one, the fourth component from the third... and always get the fields from that SQL, if I change SQL property value, it gets the fields perfectly but I don't know why it gets that value with new components

I've write this component using FastReports documentation, I don't know if I have to use another tutorial or wizard

I attach the source code

thanks

unit UDwFrxDBComponents;

interface

Uses
  System.Classes, System.SysUtils, frxClass, Data.DB, Datasnap.Win.MConnect, Datasnap.DBClient,
  frxCustomDB, USClientDataSet
  {IFDEF QBUILDER}
  , fqbClass
  {ENDIF}
 ;

type

  TDwFrxDBComponents = class(TfrxDBComponents)
  private
    FDefaultDatabase: TCustomRemoteServer;
    FOldComponents: TDwFrxDBComponents;
  protected

  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    function GetDescription: String; override;
  published
    property DefaultDatabase: TCustomRemoteServer read FDefaultDatabase write FDefaultDatabase;
  end;

  TDwFrxDBDataSet = class(TfrxCustomQuery)
  private
    FDataBase: TCustomRemoteServer;
    FQuery: SClientDataSet;
    FStrings: TStrings;
    FLock: Boolean;
    procedure SetDataBase(Value: TCustomRemoteServer);
  protected
    procedure Notification(AComponent: TComponent; Operation: TOperation); override;
    procedure OnChangeSQL(Sender: TObject); override;
    procedure SetSQL(Value: TStrings); override;
    function GetSQL: TStrings; override;
    procedure Loaded; override;
  public
    constructor Create(AOwner: TComponent); override;
    constructor DesignCreate(AOwner: TComponent; Flags: Word); override;
    destructor Destroy; override;
    class function GetDescription: String; override;
    procedure UpdateParams; override;
    procedure BeforeStartReport; override;
{$IFDEF QBUILDER}
    function QBEngine: TfqbEngine;
{$ENDIF}
    property Query: SClientDataSet read FQuery;
  published
    //property SQL;// : TStrings read FStrings write SetSQL;
    property DataBase: TCustomRemoteServer read FDataBase write SetDataBase;
  end;

{$IFDEF QBUILDER}
  TDwfrxDBEngine = class(TfqbEngine)
  private
    FQuery: SClientDataSet;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    procedure ReadTableList(ATableList: TStrings); override;
    procedure ReadFieldList(const ATableName: string; var AFieldList: TfqbFieldList); override;
    function ResultDataSet: TDataSet; override;
    procedure SetSQL(const Value: string); override;
  end;
{$ENDIF}

procedure frxParamsToTParameters(Query: TDwFrxDBDataSet; Params: TParams);

var
  DwFrxDBComponents: TDwFrxDBComponents;

implementation

uses
  UDwFrxDBComponentsRTTI,
  {$IFNDEF NO_EDITORS}
  UDwFrxDBComponentsEditor,
  {$ENDIF}
  frxDsgnIntf, frxRes;

{ frxParamsToTParameters }

procedure frxParamsToTParameters(Query: TDwFrxDBDataSet; Params: TParams);
var
  i: Integer;
  Item: TfrxParamItem;
begin

  for i := 0 to Params.Count - 1 do
    if Query.Params.IndexOf(Params[i].Name) <> -1 then
    begin
      Item := Query.Params[Query.Params.IndexOf(Params[i].Name)];
      Params[i].DataType := Item.DataType;
      Params[i].ParamType := ptInput;
      if Trim(Item.Expression) <> '' then
        if not (Query.IsLoading or Query.IsDesigning) then
        begin
          Query.Report.CurObject := Query.Name;
          Item.Value := Query.Report.Calc(Item.Expression);
        end;
      Params[i].Value := Item.Value;
    end;
end;

{ TDwFrxDBComponents }

constructor TDwFrxDBComponents.Create(AOwner: TComponent);
begin
  inherited;

  FOldComponents := DwFrxDBComponents;
  FDefaultDatabase := nil;
  DwFrxDBComponents := Self;

end;

destructor TDwFrxDBComponents.Destroy;
begin
  if DwFrxDBComponents = Self then
    DwFrxDBComponents := FOldComponents;
  inherited;
end;

function TDwFrxDBComponents.GetDescription: String;
begin
  Result := 'Digital Ware FrxDBComponents';
end;

{ TDwFrxDBDataSet }

procedure TDwFrxDBDataSet.BeforeStartReport;
begin
  SetDatabase(FDatabase);
  { needed to update parameters }
  //SQL.Text := SQL.Text;
end;

constructor TDwFrxDBDataSet.Create(AOwner: TComponent);
begin
  FStrings := TStringList.Create;
  FQuery := SClientDataSet.Create(nil);
  FQuery.ProviderName := 'DtsPTemporal';
  FQuery.Close;
  Dataset := FQuery;
  SetDataBase(nil);
  FLock := False;
  inherited;

  //SQL.Clear;

end;

constructor TDwFrxDBDataSet.DesignCreate(AOwner: TComponent; Flags: Word);
var
  i: Integer;
  l: TList;
begin
  inherited;
  l := Report.AllObjects;
  for i := 0 to l.Count - 1 do
    if TObject(l[i]) is TCustomRemoteServer then
    begin
      SetDataBase(TCustomRemoteServer(l[i]));
      break;
    end;
end;

destructor TDwFrxDBDataSet.Destroy;
begin
  FStrings.Free;
  inherited;
end;

class function TDwFrxDBDataSet.GetDescription: String;
begin
  Result := 'Digital Ware FrxDBDataset';
end;

function TDwFrxDBDataSet.GetSQL: TStrings;
begin
  FLock := True;
  //FStrings.Assign(FQuery.SQL);
  FLock := False;
  Result := FQuery.SQL;
end;

procedure TDwFrxDBDataSet.Loaded;
begin
  inherited Loaded;
  OnChangeSQL(nil);// update params after load
end;

procedure TDwFrxDBDataSet.Notification(AComponent: TComponent;
  Operation: TOperation);
begin
  inherited;
  if (Operation = opRemove) and (AComponent = FDataBase) then
    SetDataBase(nil);
end;

procedure TDwFrxDBDataSet.OnChangeSQL(Sender: TObject);
var
  i, ind: Integer;
  Param: TfrxParamItem;
  QParam: TParam;
begin
  if not FLock then
  begin
    { needed to update parameters }
    //FQuery.SQL.Text := '';
    //FQuery.SQL.Assign(FStrings);
    inherited;
    { fill datatype automatically, if possible }
    for i := 0 to FQuery.Params.Count - 1 do
    begin
      QParam := FQuery.Params[i];
      ind := Params.IndexOf(QParam.Name);
      if ind <> -1 then
      begin
        Param := Params[ind];
        if (Param.DataType = ftUnknown) and (QParam.DataType <> ftUnknown) then
          Param.DataType := QParam.DataType;
      end;
    end;
  end;

end;

{$IFDEF QBUILDER}
function TDwFrxDBDataSet.QBEngine: TfqbEngine;
begin
  Result := TDwfrxDBEngine.Create(nil);
  TDwfrxDBEngine(Result).FQuery.RemoteServer := FQuery.RemoteServer;
end;
{$ENDIF}

procedure TDwFrxDBDataSet.SetDataBase(Value: TCustomRemoteServer);
begin

  if Value <> nil then
    FQuery.RemoteServer := Value
  else if DwFrxDBComponents <> nil then
  begin
    FQuery.RemoteServer := DwFrxDBComponents.DefaultDatabase;
  end
  else
    FQuery.RemoteServer := nil;

  FDataBase := FQuery.RemoteServer;

  DBConnected := FQuery.RemoteServer <> nil;

end;

procedure TDwFrxDBDataSet.SetSQL(Value: TStrings);
begin

  FQuery.SQL := Value;
  //FStrings := FQuery.SQL;

end;

procedure TDwFrxDBDataSet.UpdateParams;
begin
  inherited;

  frxParamsToTParameters(Self, FQuery.Params);

end;

{ TDwfrxDBEngine }

{$IFDEF QBUILDER}
constructor TDwfrxDBEngine.Create(AOwner: TComponent);
begin
  inherited;
  FQuery  := SClientDataSet.Create(Self);
end;

destructor TDwfrxDBEngine.Destroy;
begin
  FQuery.Free;
  inherited;
end;

procedure TDwfrxDBEngine.ReadFieldList(const ATableName: string;
  var AFieldList: TfqbFieldList);
var
  TempTable: SClientDataSet;
  Fields: TFieldDefs;
  i: Integer;
  tmpField: TfqbField;
begin

  AFieldList.Clear;
  TempTable := SClientDataSet.Create(Self);
  TempTable.RemoteServer := FQuery.RemoteServer;
  TempTable.ProviderName := 'DtsPTemporal';
  TempTable.SQL.Text := ' SELECT * FROM ' + ATableName + ' WHERE 1=0';
  TempTable.Open;

  Fields := TempTable.FieldDefs;
  try
    try
      TempTable.Active := True;
      tmpField:= TfqbField(AFieldList.Add);
      tmpField.FieldName := '*';
      for i := 0 to Fields.Count - 1 do
      begin
        tmpField := TfqbField(AFieldList.Add);
        tmpField.FieldName := Fields.Items[i].Name;
        tmpField.FieldType := Ord(Fields.Items[i].DataType)
      end;
    except
    end;
  finally
    TempTable.Free;
  end;

end;

procedure TDwfrxDBEngine.ReadTableList(ATableList: TStrings);
begin
  inherited;
  ATableList.Clear;
end;

function TDwfrxDBEngine.ResultDataSet: TDataSet;
begin

  Result := FQuery;

end;

procedure TDwfrxDBEngine.SetSQL(const Value: string);
begin
  inherited;

  FQuery.SQL.Text := Value;

end;
{$ENDIF}

initialization
  { use standard pictures indexes 37,38,39 instead of pictures}
  frxObjects.RegisterObject1(TDwFrxDBDataSet, nil, '', '', 0, 39);

finalization
  frxObjects.Unregister(TDwFrxDBDataSet);

end.