TBlobStream.Create Constructor

Creates an instance of TBlobStream.

Pascal

constructor Create(Field: TBlobField; Mode: TBlobStreamMode);

C++

__fastcall TBlobStream(TBlobField Field, TBlobStreamMode Mode);

Description

Call Create to obtain an instance of TBlobStream for reading from or writing to a specific TBlobField object.

Tip: Different types of dataset use different classes of BLOB streams. It is usually a better idea to call the dataset's CreateBlobStream method than to call the BLOB stream constructor.

Create links the TBlobStream to the field object specified by the Field parameter. Mode specifies whether the BLOB stream will be used to read data (bmRead), write data (bmWrite) or modify data (bmReadWrite). Mode must be one of the following values:

Value	Meaning
bmRead	The BLOB stream can read data from the field.
bmWrite	The BLOB stream can replace the data in the field.
bmReadWrite	The BLOB stream can modify the data in the field.

Note: : A TBlobStream object should always be destroyed before navigating to a new record. Create a new instance of TBlobStream for the new record.

C++ Examples:

Copy Code

/*
The following example copies the data in the Notes field of
Table1 or SQLDataSet1 to the Remarks field of ClientDataSet1.
*/
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  TBlobType blobType = Table1Notes->BlobType;
  TStream *Stream1 = new TBlobStream(Table1Notes, bmRead);
  try
  {
    CDS2->Edit();
    // here’s a different way to create a blob stream }
    TStream *Stream2 = CDS2->CreateBlobStream(CDS2->FieldByName("Remarks"), bmReadWrite);
    try
    {
      Stream2->CopyFrom(Stream1, Stream1->Size);
//    CDS2.Post;
//    CDS2.Active := True;
    }
    __finally
    {
      delete Stream2;
    }
  }
  __finally
  {
    delete Stream1;
  }
};

Delphi Examples:

Copy Code

{
The following example copies the data in the Notes field of
Table1 or SQLDataSet1 to the Remarks field of ClientDataSet1.
}
procedure TForm1.Button1Click(Sender: TObject);
var
  Stream1: TBlobStream;
  Stream2: TStream;
  blobType : TBlobType;
begin
  blobType := Table1Notes.BlobType;
  Stream1 := TBlobStream.Create(Table1Notes, bmRead);
  try
    CDS2.Edit;
    { here’s a different way to create a blob stream }
    Stream2 := CDS2.CreateBlobStream(CDS2.FieldByName('Remarks'), bmReadWrite);
    try
      Stream2.CopyFrom(Stream1, Stream1.Size);
//    CDS2.Post;
//    CDS2.Active := True;
    finally
      Stream2.Free;
    end;
  finally
    Stream1.Free;
  end;
end;