delphi TClientDataSet[20]: 使用 Blob 字段

TClientDataSet[20]: 使用 Blob 字段

Blob(Binary Large Object) 字段包括:

ftBlob, 

ftMemo, 

ftGraphic, 

ftFmtMemo, 

ftParadoxOle, 

ftDBaseOle, 

ftTypedBinary, 

ftCursor, 

ftFixedChar, 

ftWideString,

ftLargeint, 

ftADT, 

ftArray, 

ftReference, 

ftDataSet, 

ftOraBlob, 

ftOraClob, 

ftVariant, 

ftInterface, 

ftIDispatch, 

ftGuid, 

ftTimeStamp, 

ftFMTBcd, 

ftFixedWideChar, 

ftWideMemo

{ TBlobType = ftBlob..ftWideMemo }

示例:

uses IOUtils, MMSystem;

{ 建立包含 Blob 字段的数据集, 并载入 Windows\Media\*.wav }

procedure TForm1.FormCreate(Sender: TObject);

var

  MediaPath, Path: string;

begin

  with ClientDataSet1 do begin

    FieldDefs.Add('WavFileName', ftString, 32);

    FieldDefs.Add('WAV', ftBlob);

    CreateDataSet;

  end;

  MediaPath := GetEnvironmentVariable('SystemRoot') + '\Media\';

  for Path in TDirectory.GetFiles(MediaPath, '*.wav') do

  begin

    ClientDataSet1.Append;

    ClientDataSet1['WavFileName'] := ExtractFileName(Path);

    TBlobField(ClientDataSet1.FieldByName('WAV')).LoadFromFile(Path);

  end;

  ClientDataSet1.MergeChangeLog;

end;

{ 播放 }

procedure TForm1.Button1Click(Sender: TObject);

var

  BlobStream: TClientBlobStream;

  BlobField: TBlobField;

begin

  BlobField := ClientDataSet1.FieldByName('WAV') as TBlobField;

  BlobStream := TClientBlobStream.Create(BlobField, bmRead);

  Win32Check(PlaySound(BlobStream.Memory, 0, SND_SYNC or SND_MEMORY));

  BlobStream.Free;

end;