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.

C++ Examples:

Copy Code

/*
  This example saves params from a ClientDataSet, alters them
  and restores them.
*/
TParams *SavedParams;

void __fastcall TForm1::SaveParamsClick(TObject *Sender)
{
  // Save the parameters for the TDataSet
  SavedParams->Assign(CDS->Params);
}

void __fastcall TForm1::AlterParamsClick(TObject *Sender)
{
  CDS->Params->CreateParam(ftInteger, "StateParam", ptInput);
  CDS->Params->CreateParam(ftInteger, "MyParam", ptInput);
  for (int i = 0; i < CDS->Params->Count; i++)
    if ((CDS->Params->Items[i]->IsNull) &&
       (CDS->Params->Items[i]->DataType == ftInteger))
      // Items is the default property, so you can omit its name
      CDS->Params->Items[i]->AsInteger = -1;
}

void __fastcall TForm1::RestoreParamsClick(TObject *Sender)
{
  // Restore the parameters to TDataSet
  CDS->Params->AssignValues(SavedParams);
}

#include <memory>       //for STL auto_ptr class

void __fastcall TForm1::FormCreate(TObject *Sender)
{
  // Initialize SavedParams
  static std::auto_ptr<TParams> _SavedParamsCleaner(SavedParams = new TParams());
}

Delphi Examples:

Copy Code

{
  This example saves params from a ClientDataSet, alters them
  and restores them.
}
var SavedParams: TParams;

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;