MFnExpression Class Reference
[OpenMaya - API module for common classes, FunctionSet classes]

#include <MFnExpression.h>

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List of all members.

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Detailed Description

Expression function set.

This class is used to create, edit, and query expression nodes.

Public Types
enum	UnitConversion { kAll, kNone, kAngularOnly }
	Unit conversion modes. More...
Public Member Functions
virtual MFn::Type	type () const
	Function set type.
virtual	~MFnExpression ()
	Destructor.
	MFnExpression ()
	Default constructor.
	MFnExpression (MObject &object, MStatus *ReturnStatus=NULL)
	Constructor.
MObject	create (const MString &expression, MObject &object=MObject::kNullObj, MStatus *ReturnStatus=NULL)
MString	expression (MStatus *ReturnStatus=NULL)
MStatus	setExpression (const MString &expression)
MStatus	getDefaultObject (MObject &object)
MStatus	setDefaultObject (MObject &object)
bool	isAnimated (MStatus *ReturnStatus=NULL)
MStatus	setAnimated (bool value=false)
MStatus	evaluate (MDoubleArray &result)
UnitConversion	unitConversion (MStatus *ReturnStatus=NULL) const
MStatus	setUnitConversion (UnitConversion conversion)
	MFnExpression (const MObject &object, MStatus *ReturnStatus=NULL)
	Constructor.
MStatus	getExpression (MString &expression)
	NO SCRIPT SUPPORT.
Protected Member Functions
virtual const char *	className () const
	Class name.

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Member Enumeration Documentation

enum MFnExpression::UnitConversion

Unit conversion modes.

Enumerator:

kAll	Convert all units.
kNone	Do not do any unit conversion.
kAngularOnly	Only convert angular units.

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Constructor & Destructor Documentation

MFnExpression::MFnExpression	(	MObject &	object,
		MStatus *	ReturnStatus = NULL
	)

Constructor.

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

Parameters:

[in]	object	The MObject to attach the function set to
[out]	ReturnStatus	the return status

Status Codes:

• 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

MFnExpression::MFnExpression	(	const MObject &	object,
		MStatus *	ReturnStatus = NULL
	)

Constructor.

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

Parameters:

[in]	object	The MObject to attach the function set to
[out]	ReturnStatus	the return status

Status Codes:

• 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

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Member Function Documentation

MFn::Type MFnExpression::type

(

)

const [virtual]

Function set type.

Return the class type : MFn::kExpression

Reimplemented from MFnDependencyNode.

const char * MFnExpression::className

(

)

const [protected, virtual]

Class name.

Return the class name : "MFnExpression"

Reimplemented from MFnDependencyNode.

MObject MFnExpression::create	(	const MString &	expression,
		MObject &	object = MObject::kNullObj,
		MStatus *	ReturnStatus = NULL
	)

This method creates and returns a dependency node for a given expression.

A default object can be specified, but if it is not specified in the expression string then the expression string values will be used.

If the expression string is of the form "objectName.attribute = ... " then the default object parameter is not needed. If you supply a default object in this case, then it will be ignored.

If the expression has no default object then you must supply one. For example, if the expression is of the form "attribute = ...", then you must supply a default object.

Parameters:

[in]	expression	The expression string
[in]	object	The default object (optional - see above)
[out]	ReturnStatus	Status code

Returns:

The expression node

Status Codes:

• MS::kSuccess
• MS::kLicenseFailure application not licensed for attempted operation
• MS::kFailure

MString MFnExpression::expression

(

MStatus *

ReturnStatus = NULL

)

Gets the expression string for this expression node.

Parameters:

[out]

ReturnStatus

Status code. See below.

Returns:

The expression string

Status Codes:

• MS::kSuccess
• MS::kFailure

MStatus MFnExpression::setExpression

(

const MString &

expression

)

Sets the expression string for this expression node.

Parameters:

[in]

expression

The expression string

Returns:

Status Code

Status Codes:

• MS::kSuccess
• MS::kFailure

MStatus MFnExpression::getDefaultObject

(

MObject &

object

)

Gets the "default" object for the expression. Not all expressions have a default object. If there is no default object for the expression, the object will be set to MObject::kNullObject and the return status will indicate success. This is a completely legal case that the calling code should check for before blindly using the returned object.

Parameters:

[out]

object

storage for the default object

Returns:

Status Code

Status Codes:

• MS::kSuccess
• MS::kFailure

MStatus MFnExpression::setDefaultObject

(

MObject &

object

)

Sets the "default" object for the expression. This allows the expression writer to not type the object name for frequently-used objects.

This method will only work for expression strings in which the object name is not specified.

Parameters:

[in]

object

the object to be set

Returns:

Status Code

Status Codes:

• MS::kSuccess
• MS::kFailure

bool MFnExpression::isAnimated

(

MStatus *

ReturnStatus = NULL

)

If this is true, then the expression will be evaluated whenever time changes, regardless of whether the other inputs have changed.

If it is false (the default) , then the expression will only be evaluated if one or more of the inputs change.

Note, if 'time' or 'frame' are inputs, then the expression will act as if this was set to true.

Parameters:

[out]

ReturnStatus

Status code

Returns:

• true expression will be evaluated whenever time changes
• false

Status Codes:

• MS::kSuccess
• MS::kFailure

MStatus MFnExpression::setAnimated

(

bool

value = false

)

Sets the way in which the expression is evaluated.

If this is true, then the expression will be evaluated whenever time changes, regardless of whether the other inputs have changed.

If it is false (the default) , then the expression will only be evaluated if one or more of the inputs change.

Note, if 'time' or 'frame' are inputs, then the expression will act as if this was set to true.

Parameters:

[in]

value

sets the objects evaluation type

Returns:

Status Code

Status Codes:

• MS::kSuccess
• MS::kFailure

MStatus MFnExpression::evaluate

(

MDoubleArray &

result

)

Evaluate this expression and return the result.

Parameters:

[out]

result

the value of the expression

Returns:

Status code

Status Codes:

• MS::kSuccess
• MS::kFailure

MFnExpression::UnitConversion MFnExpression::unitConversion

(

MStatus *

ReturnStatus = NULL

)

const

Get the unit conversion status for the expression node.

Parameters:

[out]

ReturnStatus

Status code

Returns:

The unit conversion state for this node

Status Codes:

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

MStatus MFnExpression::setUnitConversion

(

UnitConversion

conversion

)

Set the unit conversion options for the expression node.

Parameters:

[in]

conversion

unit conversion state for this node

Returns:

Status code

Status Codes:

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

MStatus MFnExpression::getExpression

(

MString &

expression

)

NO SCRIPT SUPPORT.

Gets the expression string for this expression node.

Python Notes

This method is not supported in Python. Please see the one which returns a string

Parameters:

[in]

expression

The expression string

Returns:

Status code

Status Codes:

• MS::kSuccess
• MS::kFailure