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How to save a TCollectionItem from a component to a stream (Views: 60)


Problem/Question/Abstract:

I have written a component which uses TCollections as properties. Now I need a way to save the TCollectionItems to a file. How can I do that?

Answer:

You may try these routines. I have tested them with TStatusBar.Panels collection and they worked for me:

procedure LoadCollectionFromStream(Stream: TStream; Collection: TCollection);
begin
  with TReader.Create(Stream, 4096) do
  try
    CheckValue(vaCollection);
    ReadCollection(Collection);
  finally
    Free;
  end;
end;

procedure LoadCollectionFromFile(const FileName: string; Collection: TCollection);
var
  FS: TFileStream;
begin
  FS := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
  try
    LoadCollectionFromStream(FS, Collection);
  finally
    FS.Free;
  end;
end;

procedure SaveCollectionToStream(Collection: TCollection; Stream: TStream);
begin
  with TWriter.Create(Stream, 4096) do
  try
    WriteCollection(Collection);
  finally
    Free;
  end;
end;

procedure SaveCollectionToFile(Collection: TCollection; const FileName: string);
var
  FS: TFileStream;
begin
  FS := TFileStream.Create(FileName, fmCreate or fmShareDenyWrite);
  try
    SaveCollectionToStream(Collection, FS);
  finally
    FS.Free;
  end;
end;

Note: It's obvious, the Collection variable must point to the initialized instance of a TCollection
descendant.

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