class MFnAttribute

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Inheritance:

MFnAttribute < MFnBase

public members:

	MFnAttribute ()
	MFnAttribute ( MObject & object, MStatus * ReturnStatus = NULL )
virtual	~MFnAttribute ()
virtual MFn::Type	type () const
enum	DisconnectBehavior kDelete delete array element on disconnect (array attributes only) kReset reset the attribute to its default on disconnect kNothing do nothing to the attribute's value on disconnect
bool	isReadable ( MStatus * ReturnStatus=NULL ) const
bool	isWritable ( MStatus * ReturnStatus=NULL ) const
bool	isConnectable ( MStatus * ReturnStatus=NULL ) const
bool	isStorable ( MStatus * ReturnStatus=NULL ) const
bool	isCached ( MStatus * ReturnStatus=NULL ) const
bool	isArray ( MStatus * ReturnStatus=NULL ) const
bool	indexMatters ( MStatus * ReturnStatus=NULL ) const
bool	isKeyable ( MStatus * ReturnStatus=NULL ) const
bool	isChannelBoxFlagSet ( MStatus * ReturnStatus=NULL ) const
bool	isHidden ( MStatus * ReturnStatus=NULL ) const
bool	isUsedAsColor ( MStatus * ReturnStatus=NULL ) const
bool	isIndeterminant ( MStatus * ReturnStatus=NULL ) const
bool	isRenderSource ( MStatus * ReturnStatus=NULL ) const
bool	isDynamic ( MStatus * ReturnStatus=NULL ) const
bool	isWorldSpace ( MStatus * ReturnStatus=NULL ) const
bool	isAffectsWorldSpace ( MStatus * ReturnStatus=NULL ) const
DisconnectBehavior	disconnectBehavior ( MStatus * ReturnStatus=NULL ) const
bool	usesArrayDataBuilder ( MStatus * ReturnStatus=NULL ) const
bool	internal ( MStatus * ReturnStatus=NULL ) const
MStatus	setReadable ( bool state )
MStatus	setWritable ( bool state )
MStatus	setConnectable ( bool state )
MStatus	setStorable ( bool state )
MStatus	setCached ( bool state )
MStatus	setArray ( bool state )
MStatus	setIndexMatters ( bool state )
MStatus	setKeyable ( bool state )
MStatus	setChannelBox ( bool state )
MStatus	setHidden ( bool state )
MStatus	setUsedAsColor ( bool state )
MStatus	setIndeterminant ( bool state )
MStatus	setRenderSource ( bool state )
MStatus	setWorldSpace ( bool state )
MStatus	setAffectsWorldSpace ( bool state )
MStatus	setDisconnectBehavior ( DisconnectBehavior behavior )
MStatus	setUsesArrayDataBuilder ( bool state )
MStatus	setInternal ( bool state )
bool	accepts ( MFnData::Type type , MStatus * ReturnStatus=NULL ) const
bool	accepts ( const MTypeId & id, MStatus * ReturnStatus=NULL ) const
MObject	parent ( MStatus * ReturnStatus=NULL) const
MStatus	setParent ( const MObject & parent )
MString	name ( MStatus * ReturnStatus=NULL ) const
MString	shortName ( MStatus * ReturnStatus=NULL ) const
MString	getAddAttrCmd ( bool useLongName = false, MStatus * status=NULL ) const
	public NO SCRIPT SUPPORT
	MFnAttribute ( const MObject & object, MStatus * ReturnStatus = NULL )

Inherited from MFnBase:

public members:

virtual MFn::Type	type () const
bool	hasObj ( MFn::Type ) const
bool	hasObj ( const MObject & ) const
MObject	object ( MStatus * ReturnStatus = NULL ) const
virtual MStatus	setObject ( MObject & object )
virtual MStatus	setObject ( const MObject & object )

Documentation

Description

MFnAttribute is the function set for dependency node attributes.

An attribute of a dependency node describes a piece of data that belongs to nodes of that type. For example, a node that makes a sphere might have a radius attribute. A node's attributes describe connections sites on the node that can be used in the dependency graph.

Attributes typically belong to a class of nodes, rather than to an individual node. For example, all sphere nodes have a radius. Even though a single attribute may be shared by all nodes of a given type, each node will have its own value for the attribute.

Attributes are heirarchical. For example, the translate scale attribute of a transform has x, y, and z child attributes.

By default, attributes are:

• readable
• writable
• connectable
• storable
• cached
• not arrays
• have indices that matter
• do not use an array builder
• not keyable
• not hidden
• not used as colors
• not indeterminant
• set to disconnect behavior kNothing

Functions

MFnAttribute:: MFnAttribute ()

Description

Default class constructor. The function set is not attached to an MObject.

MFnAttribute:: MFnAttribute ( MObject & object, MStatus * ReturnStatus )

Description

Class constructor that initializes the function set to the given MObject.

Arguments

• object the MObject to attach the function set to
• ReturnStatus the return status
  • MS::kSuccess if the function set is successfully attached
  • MS::kInvalidParameter if the MObject does not represent a valid Maya object or if the function set is not allowed to attach to this MObject

MFnAttribute:: MFnAttribute ( const MObject & object, MStatus * ReturnStatus )

Description

Class constructor that initializes the function set to the given constant MObject.

Arguments

• object the const MObject to attach the function set to
• ReturnStatus the return status
  • MS::kSuccess if the function set is successfully attached
  • MS::kInvalidParameter if the MObject does not represent a valid Maya object or if the function set is not allowed to attach to this MObject

MFnAttribute:: ~MFnAttribute ()

Description

The class destructor.

MFn::Type MFnAttribute:: type () const

Description

Return the type of this function set.

Return Value

• the constant MFn::kAttribute

bool MFnAttribute:: isReadable ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is readable. If an attribute is readable, then it can be used as the source in a dependency graph connection.

Attributes are readable by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is readable

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isWritable ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is writable. If an attribute is writable, then it can be used as the destination in a dependency graph connection.

Attributes are writable by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is writable

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isConnectable ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute accepts dependency graph connections. If it does, then the readable and writable methods will indicate what types of connections are accepted.

Attributes are connectable by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is connectable

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isStorable ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is to be stored when the node is saved to a file.

Attributes are storable by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is storable

Status Codes

• kSuccess operation successful
• kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isCached ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is cached locally in the node's data block. The default for this is true. Caching a node locally causes a copy of the attribute value for the node to be cached with the node. This removes the need to traverse through the graph to get the value each time it is requested.

Caching the value locally gives a speed increase at the cost of more memory.

Attributes are cached by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is cached locally

Status Codes

• kSuccess operation successful
• kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isArray ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute supports an array of data.

Attributes are single elements by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute stores an array of data

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: indexMatters ( MStatus * ReturnStatus ) const

Description

Determines whether the user must specify an index when connecting to this attribute, or whether the next available index can be used. This method only applies to array attributes which are non readable, i.e. destination attributes.

This corresponds with the connectAttr command's -na/nextAvailable flag. If the destination attribute has set the indexMatters to be false with this flag specified, a connection is made to the next available index. No index need be specified

The index matters to attributes by default.

Arguments

• ReturnStatus return status

Return Value

• true The user must specify the index when connecting to this attribute using connectAttr
• false The next available index can be used when connecting to this attribute using connectAttr -na

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isKeyable ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is keyable. Keyable attributes will be keyed by AutoKey and the Set Keyframe UI. Non-keyable attributes prevent the user from setting keys via the obvious UI provided for keying. Being non-keyable is not a hard block against adding keys to an attribute.

This method determines the default keyability of a plug. The keyability can be changed after it is created. Use the MPlug::isKeyable method to determine whether or not a specific plug is keyable.

Attributes are not keyable by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is keyable

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isChannelBoxFlagSet ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute has its channel box flag set. Attributes will appear in the channel box if their channel box flag is set or if they are keyable.

This method returns the default channel box display state of a plug. The display can be changed after it is created. Use the MPlug::isChannelBox method to determine whether or not a specific plug is displayed in the channel box.

Attributes are not in the channel box by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating the status of the channel box flag on this attribute

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isHidden ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is to hidden from the UI. The attribute will not show up in attribute editors.

Attributes are not hidden by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is hidden

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isUsedAsColor ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is to be presented as a color in the UI.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is used as a color

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isIndeterminant ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is indeterminant. If an attribute may or may not be used during an evaluation then it is indeterminant. This attribute classification is mainly used on rendering nodes to indicate that some attributes are not always used.

Attributes are not indeterminant by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is indeterminant

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isRenderSource ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is a render source. This attribute is used on rendering nodes to override the rendering sampler info.

Attributes are not render source by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is render source

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isDynamic ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is a dynamic attribute.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is dynamic

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isWorldSpace ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute is worldspace.

Attributes are not worldspace by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute is worldspace

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: isAffectsWorldSpace ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute affects worldspace.

Attributes do not affect worldspace by default.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute affects worldspace

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MFnAttribute::DisconnectBehavior MFnAttribute:: disconnectBehavior ( MStatus * ReturnStatus ) const

Description

Returns the behavior of this attribute when it is disconnected. The possible settings are as follows:

• kDelete delete the element of the array that was connected. This is only used for array attributes
• kReset reset the attribute to its default value
• kNothing leave the attribute set to its last known value

Attributes have a default disconnect behavior of kNothing.

Arguments

• ReturnStatus return status

Return Value

• the disconnect behavior

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: usesArrayDataBuilder ( MStatus * ReturnStatus ) const

Description

Returns true if this attribute uses an array data builder. If so, then the MArrayDataBuilder class may be used with this attribute.

By default array attributes do not use an array data builder.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute uses an array data builder.

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: internal ( MStatus * ReturnStatus ) const

Description

Returns true if a node has internal member data representing this attribute.

Arguments

• ReturnStatus return status

Return Value

• a boolean value indicating whether this attribute uses internal data

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setReadable ( bool state )

Description

Sets whether this attribute should be readable. If an attribute is readable, then it can be used as the source in a dependency graph connection.

Attributes are readable by default.

Arguments

• state whether the attribute is to be readable

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setWritable ( bool state )

Description

Sets whether this attribute should be writable. If an attribute is writable, then it can be used as the destination in a dependency graph connection. If an attribute is not writable then setAttr commands will fail to change the attribute.

If both keyable and writable for an attribute are set to true it will be displayed in the channel box when the node is selected.

Attributes are writable by default.

Arguments

• state whether the attribute is to be writable

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setConnectable ( bool state )

Description

Sets whether this attribute should allow dependency graph connections. This should only get called in the initialize call of your node creator.

Attributes are connectable by default.

Arguments

• state whether the attribute is to be connectable

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setStorable ( bool state )

Description

Sets whether this attribute should be storable. If an attribute is storable, then it will be writen out when the node is stored to a file. This should only get called in the initialize call of your node creator.

Attributes are storable by default.

NOTE: Typed attributes of setting MFnData::kDynArrayAttrs are not storable.

Arguments

• state whether the attribute is to be storable

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setCached ( bool state )

Description

Sets whether the data for this attribute is cached locally in the node's data block. The default for this is true. Caching a node locally causes a copy of the attribute value for the node to be cached with the node. This removes the need to traverse through the graph to get the value each time it is requested. This should only get called in the initialize call of your node creator.

Caching the value locally gives a speed increase at the cost of more memory.

Attributes are cached by default.

Arguments

• state whether the attribute is to be cached locally

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setArray ( bool state )

Description

Sets whether this attribute should have an array of data. This should be set to true if the attribute needs to accept multiple incoming connections.

Attributes are single elements by default.

Arguments

• state whether the attribute is to have an array of data

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setIndexMatters ( bool state )

Description

If the attribute is an array, then this method specifies whether to force the user to specify an index when connecting to this attribute, or to use the next available index.

This corresponds with the connectAttr command's -na/nextAvailable flag. If the destination attribute has set the indexMatters to be false with this flag specified, a connection is made to the next available index. No index need be specified

This method will only affect array attributes with setReadable set to false, i.e. destination attributes.

The index matters to attributes by default.

Arguments

• state whether the attribute's index must be specified when connecting to this attribute using the connectAttr command

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kInvalidParameter attribute is readable
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setKeyable ( bool state )

Description

Sets whether this attribute should accept keyframe data. This should only get called in the initialize call of your node creator. Keyable attributes will be keyed by AutoKey and the Set Keyframe UI. Non-keyable attributes prevent the user from setting keys via the obvious UI provided for keying. Being non-keyable is not a hard block against adding keys to an attribute.

This method changes the default state of a plug. The keyability of a specific plug can be changed using the MPlug::setKeyable method.

If both keyable and writable for an attribute are set to true it will be displayed in the channel box when the node is selected.

Attributes are not keyable by default.

Arguments

• state whether the attribute is to be keyable

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setChannelBox ( bool state )

Description

Sets whether this attribute should appear in the channel box when the node is selected. This should only get called in the initialize call of your node creator. Keyable attributes are always shown in the channel box so this flag is ignored on keyable attributes. It is for intended for use on non-keyable attributes which you want to appear in the channel box.

This method changes the default state of a plug. Channel box visibility for a specific plug can be changed using the MPlug::setChannelBox method.

Attributes are not in the channel box by default unless they are keyable.

Arguments

• state whether the attribute is to appear in the channel box

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setHidden ( bool state )

Description

Sets whether this attribute should be hidden from the UI. This is useful if the attribute is being used for blind data, or if it is being used as scratch space for a geometry calculation (should also be marked non-connectable in that case).

Attributes are not hidden by default.

Arguments

• state whether the attribute is to be hidden

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setUsedAsColor ( bool state )

Description

Sets whether this attribute should be presented as a color in the UI.

Arguments

• state whether the attribute is to be presented as a color

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setIndeterminant ( bool state )

Description

Sets whether this attribute is indeterminant. If an attribute may or may not be used during an evaluation then it is indeterminant. This attribute classification is mainly used on rendering nodes to indicate that some attributes are not always used.

Attributes are not indeterminant by default.

Arguments

• state whether the attribute indeterminant

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setRenderSource ( bool state )

Description

Sets whether this attribute should be used as a render source attribute. When writing shader plug-ins, it is sometimes useful to be able to modify the sampler info, so upstream shading network can be re- evaluated with different sampler info values.

For example, if a shading node takes a 2D texture as input, the result color of the 2D texture is evaluated at the current sample's UV coordinates. Initializing uvCoords attributes as render source and modifing the U and V values, then setting it as output will modify the sampler info. Re-evaluating the input plug will cause the 2D texture to re-evaluate with the new U and V values, and return a different color to the shading node.

Only valid Maya rendering attributes can be set to render source.

The following code example demonstrates how this is done:

initialize()

...

// creates attributes for uvCoord and set them to be render source

u = nAttr.create( "uCoord", "u", MFnNumericData::kFloat, 0.0 ); nAttr.setStorable(false); nAttr.setWritable(true); nAttr.setRenderSource(true); v = nAttr.create( "vCoord", "v", MFnNumericData::kFloat, 0.0 ); nAttr.setStorable(false); nAttr.setWritable(true); nAttr.setRenderSource(true); uv = nAttr.create( "uvCoord", "uv", u, v ); nAttr.setStorable(false); nAttr.setWritable(true); nAttr.setRenderSource(true);

// need to have the output uv affect the input uv // because we want the new uv values we set to // cause other inputs to this node to evaluate

attributeAffects ( uv, uv );

...

compute()

...

// get uv coordinates from the sampler

MDataHandle uH = data.inputValue( u, &stat); MDataHandle vH = data.inputValue( v, &stat); float oldU = uH.asFloat(); float oldV = vH.asFloat();

// get shading color input at the current sampler's uv coordinates

MDataHandle colorH = data.inputValue( inColor, &stat); MFloatVector color = colorH.asFloatVector(); // color at the sampled uv location

// // evaluate input color at a different uv location: //

// set output uv coordinates back to sampler // this is only possible because we've set uv to be render source

MDataHandle outUV = data.outputValue( uv ); outUV.set( oldU-0.01, oldV-0.01 );

// get newly evaluated inColor at uv(oldU-0.01, oldV-0.01)

// any shading node connected to inColor will get uvCoord // values as we've supplied. Calling data.inputValue( inColor, &stat) // causes it to re-evaluate the network again with the new // uvCoord values.

colorH = data.inputValue( inColor, &stat); // evaluate again color = colorH.asFloatVector(); // color at the new uv location

...

outUV.set( oldU, oldV ); // set the values back before we exit

...

Arguments

• state whether the attribute is to be a render source

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setWorldSpace ( bool state )

Description

Sets whether this attribute should be treated as worldspace. Being worldspace indicates the attribute is dependent on the worldSpace transformation of this node, and will be marked dirty by any attribute changes in the hierarchy that affects the worldSpace transformation. The attribute needs to be an array since during instancing there are multiple worldSpace paths to the node & Maya requires one array element per path for worldSpace attributes.

NOTES: 1. Can only be used on array attributes. 2. This property is ignored on non-dag nodes.

Arguments

• state whether the attribute is to be presented as worldspace

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object or the attribute is not an array

MStatus MFnAttribute:: setAffectsWorldSpace ( bool state )

Description

Sets whether this attribute should affect worldspace. NOTES: This property is ignored on non-dag nodes.

Arguments

• state whether the attribute should affect worldspace

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setDisconnectBehavior ( MFnAttribute::DisconnectBehavior behavior )

Description

Sets the disconnection behavior for this attribute. This determines what happens when a connection to this attribute is deleted. This should only get called in the initialize call of your node creator.

The settings are as follows:

• kDelete delete the element of the array that was connected. This is only used for array attributes
• kReset reset the attribute to its default value
• kNothing leave the attribute set to its last known value

Attributes have a default disconnect behavior of kNothing.

Arguments

• behavior the new disconnect behavior

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setUsesArrayDataBuilder ( bool state )

Description

Sets whether this attribute uses an array data builder. If true, then the MArrayDataBuilder class may be used with this attribute to generate its data. If false, MArrayDataHandle::builder will fail.

By default array attributes do not use an array data builder.

Arguments

• state whether the attribute uses an array data builder

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MStatus MFnAttribute:: setInternal ( bool state )

Description

The function controls an attribute's data storage. When set to true, the virtual methods MPxNode::setInternalValueInContext() and MPxNode::getInternalValueInContext() are invoked whenever the attribute value is set or queried, respectively. By default, attributes are not internal.

There are two reasons to set an attribute as 'internal'. The first, and simplest, is when you want notification that the attribute has been set, or queried. This allows you to invoke some related action. In this case getInternalValueInContext() and setInternalValueInContext() should return false to indicate that Maya can store the attribute's value in the data block, instead of your own custom structure.

The second use of internal attributes is to store the data in a structure other than the datablock. When MPxNode::setInternalValueInContext() is called, the attribute's data can be transferred into your custom data structure. When getInternalValueInContext() is called, you can return your data. In this case getInternalValueInContext() and setInternalValueInContext() should return true to indicate that Maya should not store the attribute's value in the data block but use your own custom structure instead.

Arguments

• state whether the attribute uses internal data

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: accepts ( MFnData::Type type , MStatus * ReturnStatus ) const

Description

Returns true if this attribute can accept a connection of the given type.

Arguments

• type data type
• ReturnStatus return status

Return Value

• a boolean value indicating whether a connection of that type is valid

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

bool MFnAttribute:: accepts ( const MTypeId & id, MStatus * ReturnStatus ) const

Description

Returns true if this attribute can accept a connection of the given type.

Arguments

• id data type id
• ReturnStatus return status

Return Value

• a boolean value indicating whether a connection of that type is valid

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MObject MFnAttribute:: parent ( MStatus * ReturnStatus ) const

Description

Get the parent of this attribute, if it has one.

Arguments

• ReturnStatus return status

Return Value

• the parent attribute

Status Codes

• MS::kSuccess operation successful
• MS::kNotFound the attribute does not have a parent
• MS::kFailure function set does not have a valid object

MStatus MFnAttribute:: setParent ( const MObject & parent )

Description

Sets the parent attribute for this attribute. If the attribute was already a member of a compound, it will be removed from that attribute structure, and added to the specified one.

Arguments

• parent the parent attribute

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kInvalidParameter the parent object is not a valid attribute
• MS::kFailure this function set does not have a valid attribute object

MString MFnAttribute:: name ( MStatus * ReturnStatus ) const

Description

Returns the long name of the attribute. If the attribute has no long name then its short name is returned.

Arguments

• ReturnStatus The status of the resulting operation.

Return Value

• {/bf name} The name of the attribute.

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MString MFnAttribute:: shortName ( MStatus * ReturnStatus ) const

Description

Returns the short name of the attribute. If the attribute has no short name then its long name is returned.

Arguments

• ReturnStatus The status of the resulting operation.

Return Value

• {/bf name} The name of the attribute.

Status Codes

• MS::kSuccess operation successful
• MS::kFailure this function set does not have a valid attribute object

MString MFnAttribute:: getAddAttrCmd (bool useLongName, MStatus * status) const

Description

Returns a string containing the addAttr command which would be required to recreate the attribute on a node. The command includes the terminating semicolon and is formatted as if for use with a selected node, meaning that it contains no node name.

To get the addAttr commands for a compound attribute and its children, use MFnCompoundAttribute::getAddAttrCmds.

Arguments

• useLongName if true, use the attribute's long name rather than its short name
• cmd a string to receive the addAttr command

Return Value

• return status

Status Codes

• MS::kSuccess operation successful
• MS::kFailure operation failed
• MS::kInvalidParameter function set is not bound to an attribute

Direct child classes:

- MFnUnitAttribute
- MFnTypedAttribute
- MFnNumericAttribute
- MFnMessageAttribute
- MFnMatrixAttribute
- MFnLightDataAttribute
- MFnGenericAttribute
- MFnEnumAttribute
- MFnCompoundAttribute