TBoldAttribute¶

Superclass to all attribute classes in Bold

Declaration¶

TBoldAttribute = class(TBoldMember)

Hierarchy¶

TObject
TBoldMemoryManagedObject
TBoldFlaggedObject
TBoldSubscribableObject
TBoldElement
TBoldDomainElement
TBoldMember
TBoldAttribute
Direct subclasses
TBABlob
TBAMoment
TBANumeric
TBAString
TBAValueSet

Description¶

Attributes are used for two different purposes.

First of all they are used to be attributes of business objects (subclasses of TBoldObject). In this role they can be persistent, or transient, they can also be derived (calculated). When used as the attribute of a business object, the property BoldAttributeRTInfo will always be assigned, and indicate the role of the attribute in the model.

TBoldAttribute can also be created independent of a business object. This happens frequently when OCL expressions are evaluated, and the result is a calculated value (concatenation of two strings for example). It is also allowed to call the constructor of a concrete subclass of TBoldAttribute. Often however when attributes are used stand-alone, it is more convenient to use the TBoldVariableHandle, or the TBoldMemberFactory to create the attribute-object.

Every subclass of TBoldAttribute has its own internal data, and usually it has an access-property to read and write the contents of the attribute object in the native format. Most attribute types also implement the AsString property to allow reading and writing the string representation of the attribute.

To subclass TBoldAttribute, the easiest way is to use the Attribute-wizard found in the Bold menu in the Delphi/C++Builder IDE.

Properties¶

Name	Summary	Notes
BoldAttributeRTInfo		read-only
ContentIsNull	Bold-internal check for NULL	protected, read-only
IsNull	If the attribute has the special 'empty' value NULL.	read-only

BoldAttributeRTInfo¶

property BoldAttributeRTInfo: TBoldAttributeRTInfo;

This property is the same as BoldMemberRTInfo, but downcasted to TBoldAttributeRTInfo.

ContentIsNull¶

property ContentIsNull: Boolean;

Bold-internal variant of IsNull

IsNull¶

property IsNull: Boolean;

Note that Null is a special value and that it in most cases is an error to access the basic representation of the attribute, e.g. AsInteger, if IsNull is True.

An attribute can be set to Null with SetToNull. An attribute is set to a non-Null value by setting the value.

Methods¶

Name	Summary	Notes
Assign	Overridden from Assign	override
AssignContentValue	Assigns the internal value	protected, abstract
AssignValue	Assigns the internal state	protected, abstract
CanSetToNull
CompareToAs	Overriddden from CompareToAs	override
DefaultSubscribe	Subscribes to default events on the attribute.	override
DoSetInitialValue	Bold-internal	protected, override
EitherIsNull	True if IsNull is true for either of the arguments.	protected
EnsureNotNull	Called by subclasses to guard against NULL values.	protected
FormatFailure	Convenience function for subclasses for setting the failure reason.	protected
GetContentIsNull	Get-method for ContentIsNull property	protected
GetStreamName	Overrides TBoldMember.GetStreamName	protected, override
IsEqualToValue	Overrides TBoldMember.IsEqualToValue.	override
NullBiggest	Internal convenience method for comparing NULL values.	protected
NullSmallest	Internal convenience method for comparing NULL values.	protected
ProxyInterface	Overrides TBoldDomainElement.ProxyInterface.	override
RecycleValue	Bold-internal
SetContentToNull	Sets the internal data value to NULL.	protected
SetEmptyValue	Set the attribute to an 'empty' value	virtual
SetToNonNull	Set the attribute to a non-null value.	protected
SetToNull	Sets the attribute to the special value Null.	virtual
SubscribeToStringRepresentation	Overrides TBoldElement.SubscribeToStringRepresentation	override

Assign¶

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

Overridden from Assign

AssignContentValue¶

procedure AssignContentValue(Source: IBoldValue); virtual; abstract;

This is an internal assigning method. It sets the internal data value of the attribute only.

AssignValue¶

procedure AssignValue(Source: IBoldValue); virtual; abstract;

This is an internal assigning method. It sets the internal data value of the attribute and the persistence state from the source value.

CanSetToNull¶

function CanSetToNull(Subscriber: TBoldSubscriber): Boolean;

Returns True if the member may be set to Null. A programmer can disallow reading a member by subscribing to the bqMaySetToNull query. If a Subscriber is passed to the function, subscriptions will be placed to notify when the result of MaySetToNull may have changed. The mode information for the attribute may indicate that the attribute is not allowed to be set to null.

CompareToAs¶

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

Overriddden from CompareToAs

DefaultSubscribe¶

procedure DefaultSubscribe(Subscriber: TBoldSubscriber; RequestedEvent: TBoldEvent = breReEvaluate); override; See also Ancestor Method

Subscribes to default events on the attribute. This will give a subscription on beValueChanged.

See Also

Subscriptions

DoSetInitialValue¶

procedure DoSetInitialValue; override; See also Ancestor Method

Bold-internal

EitherIsNull¶

class function EitherIsNull(Attribute1, Attribute2: TBoldAttribute): Boolean;

True if IsNull is true for either of the arguments.

EnsureNotNull¶

procedure EnsureNotNull;

Called by subclasses to guard against NULL values. If the attribute is NULL the exception EBoldAccessNullValue is raised.

FormatFailure¶

procedure FormatFailure(const value, ExpectedDataType: String);

Convenience function for subclasses for setting the failure reason. See SetBoldLastFailureReason.

GetContentIsNull¶

function GetContentIsNull: Boolean;

Get-method for ContentIsNull property

GetStreamName¶

function GetStreamName: string; override; See also Ancestor Method

Overrides GetStreamName

IsEqualToValue¶

function IsEqualToValue(Value: IBoldValue): Boolean; override; See also Ancestor Method

Overrides IsEqualToValue.

NullBiggest¶

function NullBiggest(BoldElement: TBoldElement): Integer;

Internal convenience method for comparing NULL values. NULL is considered bigger than any other value.

NullSmallest¶

function NullSmallest(BoldElement: TBoldElement): Integer;

Internal convenience method for comparing NULL values. NULL is considered smaller than any other value.

ProxyInterface¶

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

Overrides ProxyInterface.

RecycleValue¶

procedure RecycleValue;

Bold-internal

SetContentToNull¶

procedure SetContentToNull;

Sets the internal data value to NULL. Used by subclasses and persistence mechanisms. To set an attribute to NULL normally, use SetToNull.

SetEmptyValue¶

procedure SetEmptyValue; virtual;

All attributes (descendents of TBoldAttribute), such as TBAString, should implement this method and set the value of the attribute to an 'empty' value, such as an empty string or zero. This is to support the assign operation with no source argument.

SetToNonNull¶

procedure SetToNonNull;

This method should only be called by descendents of TBoldAttribute, such as TBAString, in the implementation of the Set-method(s) when the attribute is set to a non-NULL value.

SetToNull¶

procedure SetToNull; virtual;

Sets the attribute to the special value Null. This requires that AllowNull for the attribute is True in the model. See also CanSetToNull.

See Also

Related Topics

SubscribeToStringRepresentation¶

procedure SubscribeToStringRepresentation(Representation: TBoldRepresentation; Subscriber: TBoldSubscriber; RequestedEvent: TBoldEvent = breReEvaluate); override; See also Ancestor Method

This is equivalent to calling DefaultSubscribe unless overridden by a concrete subclass.

See Also

Subscriptions

Generated from the Bold 4.0 help (Help/BfD.chm) by Tools/chm2mkdocs.py; member lists reflect Bold 4.0, see the source for members added since.