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TBABlob

TBABlob stores binary large object data using TBoldBlobStream. Suitable for files, images, documents, and any binary content.

Class Hierarchy

classDiagram
    class TBoldAttribute {
        <<abstract>>
    }
    TBoldAttribute <|-- TBABlob
    TBABlob <|-- TBATypedBlob
    TBABlob <|-- TBABlobImageJPEG
    TBABlob <|-- TBABlobImageBMP

    class TBABlob {
        +AsStream TBoldBlobStream
        +BlobSize Int64
        +LoadFromFile()
        +SaveToFile()
    }
    class TBATypedBlob {
        +ContentType string
    }

    click TBoldAttribute href "../TBoldAttribute/" "TBoldAttribute documentation"
Loading

Class Definition

TBABlob = class(TBoldAttribute)
public
  destructor Destroy; override;
  procedure SetToNull; override;
  procedure Assign(Source: TBoldElement); override;
  procedure SetEmptyValue; override;
  procedure LoadFromStream(Stream: TStream);
  procedure LoadFromFile(const aFileName: string; aMode: Word = fmShareDenyNone);
  procedure SaveToStream(Stream: TStream);
  procedure SaveToFile(const FileName: string);
  function CompareToAs(CompareType: TBoldCompareType; BoldElement: TBoldElement): Integer; override;
  property AsStream: TBoldBlobStream read GetAsStream;
  property BlobSize: Int64 read GetBlobSize;
  property ContentType: string; // via StringRepresentation
end;

TBATypedBlob = class(TBABlob)
public
  // Adds explicit ContentType property
  function CanSetContentType(Value: string; Subscriber: TBoldSubscriber): Boolean;
end;

TBoldBlobStream

The blob's data is accessed through TBoldBlobStream, which extends TStream:

TBoldBlobStream = class(TStream)
public
  procedure Clear;
  procedure Truncate;
  procedure LoadFromStream(Stream: TStream);
  procedure LoadFromFile(const aFileName: string);
  procedure SaveToStream(Stream: TStream);
  procedure SaveToFile(const FileName: string);
  function IsDataSame(AData: Pointer; ASize: Int64): Boolean;
end;

Working with TBABlob

Loading and Saving Files

// Load a file into a blob attribute
Document.M_Attachment.LoadFromFile('C:\Reports\annual.pdf');

// Save blob to file
Document.M_Attachment.SaveToFile('C:\Temp\export.pdf');

Working with Streams

// Load from stream
var MemStream: TMemoryStream;
MemStream := TMemoryStream.Create;
try
  MemStream.LoadFromFile('image.jpg');
  Product.M_Photo.LoadFromStream(MemStream);
finally
  MemStream.Free;
end;

// Read via stream
Product.M_Photo.AsStream.SaveToFile('output.jpg');

Checking Size and Content

// Check if blob has data
if Product.M_Photo.IsNull then
  ShowMessage('No photo');

// Check size
ShowMessage(Format('Size: %d bytes', [Product.M_Photo.BlobSize]));

Typed Blobs

TBATypedBlob adds a MIME-type content type:

// Set content type for a typed blob
Document.M_Attachment.ContentType := 'application/pdf';

Blob Subtypes

Type Purpose Content Type
TBABlob Generic binary data None
TBATypedBlob Binary with MIME type User-defined
TBABlobImageJPEG JPEG images image/jpeg
TBABlobImageBMP BMP images image/bmp

See Also