[Overview][Constants][Types][Classes][Procedures and functions][Index] | Reference for unit 'db' (#fcl)

# TBlobField

[Properties (by Name)] [Methods (by Name)] [Events (by Name)]

Base class for BLOB field data

## Declaration

Source position: db.pas line 795

`type TBlobField = class(TField)`
`protected`
`procedure FreeBuffers; override;`
`function GetAsString; override;`
`function GetAsVariant; override;`
`function GetBlobSize; virtual;`
`function GetIsNull; override;`
`procedure GetText(); override;`
`procedure SetAsString(); override;`
`procedure SetText(); override;`
`procedure SetVarValue(); override;`
`function GetAsWideString; override;`
`procedure SetAsWideString(); override;`
`public`
`constructor Create(); override;` |  | Create a new instance of a TBlobField class.
`procedure Clear; override;` |  | Clear the BLOB field's contents
`public`
`class function IsBlob; override;` |  | Is the field a blob field
`public`
`procedure LoadFromFile();` |  | Load the contents of the field frop a file
`procedure LoadFromStream();` |  | Load the field's contents from stream
`procedure SaveToFile();` |  | Save field contents to a file
`procedure SaveToStream();` |  | Save the field's contents to stream
`procedure SetFieldType(); override;` |  | Set field type
`property BlobSize: LongInt; [r]` |  | Size of the current blob
`property Modified: Boolean; [rw]` |  | Has the field's contents been modified.
`property Value: String; [rw]` |  | Return the field's contents as a string
`property Transliterate: Boolean; [rw]` |  | Should the contents of the field be transliterated
`published`
`property BlobType: TBlobType; [rw]` |  | Type of blob
`property Size;` |  | Size of the blob field
`end;`

## Inheritance

`TBlobField` |  | Base class for BLOB field data
`TField` |  | Provide access to the contents of a single field in a record
`TComponent,IUnknown,IInterfaceComponentReference`
`TPersistent`
`TObject`

## Description

TBLobField is the class used when a dataset must manage BLOB data. (TField.DataType equals ftBLOB). It initializes some of the properties of the TField class, and overrides some of its methods to be able to work with BLOB fields. It also serves as parent class for some specialized blob-like field types such as TMemoField, TWideMemoField or TGraphicField

It should never be necessary to create an instance of TBlobField manually, a field of this class will be instantiated automatically for each BLOB field when a dataset is opened.

## See also

TDataset |  | Base class for records-based data-access
TField |  | Provide access to the contents of a single field in a record
TMemoField |  | Base class for MEMO (text BLOB) field data
TWideMemoField |  | Field class for wide MEMO (widestring text BLOB) field data
TGraphicField |  | Field class for graphical BLOB field data

The latest version of this document can be found at lazarus-ccr.sourceforge.net .