TCollection.Assign Method

Copies the contents of another collection to the object where the method is executed.

Pascal

procedure Assign(Source: TPersistent); override;

C++

virtual __fastcall Assign(TPersistent * Source);

Description

Use Assign to copy the contents of one TCollection instance to another. The Assign method deletes all items from the destination collection (the object where it is executed), then adds a copy of each item in the source collection's Items array.

Source is another object (typically another collection) that contains the items that replace this collection's items.

Delphi Examples:

Copy Code

{
  This example saves params from a ClientDataSet, alters them
  and restores them.
}
procedure TForm1.SaveParamsClick(Sender: TObject);
begin
  { Save the parameters for the TDataSet }
  SavedParams.Assign(CDS.Params);
end;

procedure TForm1.AlterParamsClick(Sender: TObject);
var
  I : Integer;
  ListItem: string;
begin
  CDS.Params.CreateParam(ftString, 'stringParam', ptInput);  // you can also edit the params in the CDS dynamically
  CDS.Params.CreateParam(ftSmallInt, 'smallIntParam', ptInput);
  CDS.Params.CreateParam(ftInteger, 'intParam', ptInput);
  CDS.Params.CreateParam(ftWord, 'wordParam', ptInput);
  CDS.Params.CreateParam(ftBoolean, 'boolParam', ptInput);
  CDS.Params.CreateParam(ftFloat, 'floatParam', ptInput);
  CDS.Params.CreateParam(ftCurrency, 'currencyParam', ptInput);
  CDS.Params.CreateParam(ftBCD, 'bcdParam', ptInput);
  CDS.Params.CreateParam(ftDate, 'dateParam', ptInput);
  CDS.Params.CreateParam(ftTime, 'timeParam', ptInput);
  CDS.Params.CreateParam(ftDateTime, 'dateTimeParam', ptInput);
  { Call FetchParams to ensure parameters reflect server metadata }
  CDS.FetchParams;
  with CDS.Params do
  begin
    for I := 0 to Count - 1 do
    begin
      ListItem := ListBox1.Items[I];
      case Items[I].DataType of
        ftString:
          Items[I].AsString := ListItem;
        ftSmallInt:
          Items[I].AsSmallInt := StrToIntDef(ListItem, 0);
        ftInteger:
          Items[I].AsInteger := StrToIntDef(ListItem, 0);
        ftWord:
          Items[I].AsWord := StrToIntDef(ListItem, 0);
        ftBoolean:
          begin
            if ListItem = 'True' then
              Items[I].AsBoolean := True
            else
              Items[I].AsBoolean := False;
          end;
        ftFloat:
          Items[I].AsFloat := StrToFloat(ListItem);
        ftCurrency:
          Items[I].AsCurrency := StrToFloat(ListItem);
        ftBCD:
          Items[I].AsBCD := StrToCurr(ListItem);
        ftDate:
          Items[I].AsDate := StrToDate(ListItem);
        ftTime:
          Items[I].AsTime := StrToTime(ListItem);
        ftDateTime:
          Items[I].AsDateTime := StrToDateTime(ListItem);
      end;
    end;
  end;
end;

procedure TForm1.RestoreParamsClick(Sender: TObject);
begin
  { Restore the parameters to TDataSet }
  CDS.Params.AssignValues(SavedParams);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  { Initialize SavedParams }
  SavedParams := TParams.Create;
  ListBox1.Items.Add('Here is a string');
  ListBox1.Items.Add('4');
  ListBox1.Items.Add('3456789');
  ListBox1.Items.Add('34');
  ListBox1.Items.Add('0');
  ListBox1.Items.Add('12.56');
  ListBox1.Items.Add('4.23');
  ListBox1.Items.Add('99.5');
  ListBox1.Items.Add('4/12/53');
  ListBox1.Items.Add('7:45:00');
  ListBox1.Items.Add('4/12/53 7:45:00');
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  SavedParams.Free;
end;

Copy Code

{
  This example saves params from a ClientDataSet, alters them
  and restores them.
}
procedure TForm1.SaveParamsClick(Sender: TObject);
begin
  { Save the parameters for the TDataSet }
  SavedParams.Assign(CDS.Params);
end;

procedure TForm1.AlterParamsClick(Sender: TObject);
var
  I : Integer;
begin
  CDS.Params.CreateParam(ftInteger, 'StateParam', ptInput);
  CDS.Params.CreateParam(ftInteger, 'MyParam', ptInput);
  for I := 0 to CDS.Params.Count - 1 do
    if (CDS.Params.Items[I].IsNull) and
       (CDS.Params.Items[I].DataType = ftInteger) then
      { Items is the default property, so you can omit its name }
      CDS.Params[I].AsInteger := -1;
end;

procedure TForm1.RestoreParamsClick(Sender: TObject);
begin
  { Restore the parameters to TDataSet }
  CDS.Params.AssignValues(SavedParams);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  { Initialize SavedParams }
  SavedParams := TParams.Create;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  SavedParams.Free;
end;