TBABlob¶

Attribute type for Binary Large Objects (BLOB)

Declaration¶

TBABlob = class(TBoldAttribute)

Hierarchy¶

TObject
TBoldMemoryManagedObject
TBoldFlaggedObject
TBoldSubscribableObject
TBoldElement
TBoldDomainElement
TBoldMember
TBoldAttribute
TBABlob
Direct subclasses
TBABlobImageBMP
TBABlobImageJPEG
TBATypedBlob

Description¶

This attribute type can be used to store binary data of any kind (images, formatted text, sound...). Normally they will be stored as binary data in a persistent storage.

The data value of the blob can be retrieved using either the AsString-property, or using the method CreateBlobStream.

Properties¶

Name	Summary	Notes
ContentType

ContentType¶

property ContentType: string;

This property will always be empty of the object is a TBABlob, but subclasses can use this to describe the type of the blob data.

Methods¶

Name	Summary	Notes
Assign		override
AssignContentValue		protected, override
AssignValue		override
CanSetValue
CompareToAs		override
CreateBlobStream
FreeContent	Releases the content from the attribute.	protected, override
GetAsBlob		protected
GetAsVariant		override
GetStringRepresentation		protected, override
IsEqualAs	Compares attribute content.	override
MaySetValue	Override to affect the result of CanSetValue .	protected, virtual
ProxyClass		protected, override
ProxyInterface		override
SetAsBlob		protected
SetAsVariant		override
SetEmptyValue	SetEmptyValue will set the content to empty string.	override
SetStringRepresentation		protected, override
SetToNull		override

Assign¶

procedure Assign(Source: TBoldElement); override; See also Ancestor Method

Copies data from another instance of TBABlob. The source is a blob with a ContentType but the target is a TBABlob (and not a subclass), the blobdata will be copied, but content type will be lost (no exception will occur).

AssignContentValue¶

procedure AssignContentValue(Source: IBoldValue); override; See also Ancestor Method

AssignValue¶

procedure AssignValue(Source: IBoldValue); override; See also Ancestor Method

CanSetValue¶

function CanSetValue(NewValue: string; Subscriber: TBoldSubscriber): Boolean;

Use this function to test if it is allowed to set the attribute to a specific value.

If a subscriber is sent to the function, this subscriber will be notified if the conditions have changed (so that an illegal value is now legal). It is OK to send a nilpointer instead.

CompareToAs¶

function CompareToAs(CompareType: TBoldCompareType; BoldElement: TBoldElement): Integer; override; See also Ancestor Method

CreateBlobStream¶

function CreateBlobStream(Mode: TBoldBlobStreamMode): TBoldBlobStream;

This will create a subclass of TStream that will read and write from the blob attribute. The mode-parameter indicates if the stream is readable, writeable or both.

FreeContent¶

procedure FreeContent; override; See also Ancestor Method

FreeContent resets the content of the blob attribute.

GetAsBlob¶

function GetAsBlob: String;

GetAsVariant¶

function GetAsVariant: Variant; override; See also Ancestor Method

GetStringRepresentation¶

function GetStringRepresentation(Representation: TBoldRepresentation): string; override; See also Ancestor Method

IsEqualAs¶

function IsEqualAs(CompareType: TBoldCompareType; BoldElement: TBoldElement): Boolean; override; See also Ancestor Method

IsEqualAs will compare the data content of the attribute with the content in the BoldElement submitted as parameter.

If the parameter is not a TBABlob the inherited method will be invoked.

Comparison will yield true if both the Blob and the submitted blob are null or if their data content is equal.

MaySetValue¶

function MaySetValue(NewValue: String; Subscriber: TBoldSubscriber): Boolean; virtual;

A subclass of TBABlob may override this method to prohibit setting the attribute to a specific value. If the result value is false, the setting will be aborted. If it is true, there may still be other reasons why the changing of the value is not allowed.

ProxyClass¶

function ProxyClass: TBoldMember_ProxyClass; override; See also Ancestor Method

ProxyInterface¶

function ProxyInterface(const IId: TGUID; Mode: TBoldDomainElementProxyMode; out Obj): Boolean; override; See also Ancestor Method

SetAsBlob¶

procedure SetAsBlob(NewValue: String);

SetAsVariant¶

procedure SetAsVariant(const Value: Variant); override; See also Ancestor Method

SetEmptyValue¶

procedure SetEmptyValue; override; See also Ancestor Method

SetEmptyValue will set the AsString property of the TBABlob to en empty string.

SetStringRepresentation¶

procedure SetStringRepresentation(Representation: TBoldRepresentation; Value: string); override; See also Ancestor Method

SetToNull¶

procedure SetToNull; override; See also Ancestor Method

Set the value of the attribute to Null. If Null is not an allowed value for the attribute, an exception will be raised. As an optimization, the data part of the attribute will be disposed.

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