scripted/pyMetaDataCmd.py

import sys
import os

import maya.api.OpenMaya as om

"""
To use, make sure that pyMetaDataCmd.py is in your MAYA_PLUG_IN_PATH
then do the following:

Select a node

import maya
maya.cmds.loadPlugin("pyMetaDataCmd.py")
maya.cmds.pyMetaData()

There should now be an extra attribute on your node called:
ownerName
with your user name as its string value
"""


def maya_useNewAPI():
    """
    The presence of this function tells Maya that the plugin produces, and
    expects to be passed, objects created using Maya Python API 2.0.
    """
    pass


class PyMetaDataCmd(om.MPxCommand):
    """
    Plug-in command named 'pyMetaData'.
    
    pyMetaData adds a dynamic string attribute to selected dependency nodes.
    Or, node names or a list of node names may be passed to the command.
    Dynamic attributes on nodes can be used as meta-data.

    The force/f flag is used to specify the command will overwrite existing
    dynamic string attributes of the same name.
    False will prevent overwriting pre-existing attributes.
    (default False)

    The value/v flag is used to specify a value to be set on the new attribute.
    (default user name from USERNAME or USER envar)

    The name/n flag is used to specify a name string used to name the attribute.
    (default 'userName')

    Undo/redo are supported.

    This command is written using Maya Python API 2.0.

    Example of usage, MEL:
    
    pyMetaData;
    pyMetaData -f; 
    pyMetaData -force -name priorityLevel -value High;
    pyMetaData -name health -v sick pSphere1 pSphere2;

    Example of usage, Python:
    
    maya.cmds.pyMetaData()
    maya.cmds.pyMetaData(f=True)
    maya.cmds.pyMetaData(force=True, name='priorityLevel', value='High')
    maya.cmds.pyMetaData('pSphere1','pSphere2',name='health', v='sick')
    maya.cmds.pyMetaData(['pSphere1','pSphere2'],name='health', v='sick')
    """

    # Variables to be used in Class 
    #
    cmdName = 'pyMetaData'

    nameFlag = '-n'
    nameFlagLong = '-name'

    forceFlag = '-f'
    forceFlagLong = '-force'

    valueFlag = '-v'
    valueFlagLong= '-value'


    def __init__(self):
        om.MPxCommand.__init__(self)

    @staticmethod
    def creator():
        return PyMetaDataCmd()

    @staticmethod
    def createSyntax():
        """
        Using kSelectionList in setObjectType
        and calling useSelectionAsDefault(True),
        allows us to use either a command line list of nodes,
        or use the active selection list if no node names are specified.
        
        The force/f flag is defined as requiring no arguments.
        By not specifying any arguments for the flag when we define it,
        the flag will not require any arguments when used in MEL,
        it will still require a value of 'True' or 'False' when used in Python.
        """
        syntax = om.MSyntax()
        syntax.setObjectType(om.MSyntax.kSelectionList)
        syntax.useSelectionAsDefault(True)
        syntax.addFlag(PyMetaDataCmd.forceFlag, PyMetaDataCmd.forceFlagLong)
        syntax.addFlag(PyMetaDataCmd.nameFlag, PyMetaDataCmd.nameFlagLong, om.MSyntax.kString)
        syntax.addFlag(PyMetaDataCmd.valueFlag, PyMetaDataCmd.valueFlagLong, om.MSyntax.kString)
        return syntax

    def doIt(self, args):
        # Use an MArgDatabase to Parse our command
        #
        try:
            argdb = om.MArgDatabase(self.syntax(), args)
        except RuntimeError:
            om.MGlobal.displayError('Error while parsing arguments:\n#\t# If passing in list of nodes, also check that node names exist in scene.')
            raise

        # SELECTION or LIST of Node Names
        #
        selList = argdb.getObjectList()

        # FORCE
        #
        force = argdb.isFlagSet(PyMetaDataCmd.forceFlag)

        # NAME
        #
        if argdb.isFlagSet(PyMetaDataCmd.nameFlag):
            name = argdb.flagArgumentString(PyMetaDataCmd.nameFlag, 0)
        else:
            name = 'ownerName'

        # VALUE
        #
        if argdb.isFlagSet(PyMetaDataCmd.valueFlag):
            value = argdb.flagArgumentString(PyMetaDataCmd.valueFlag, 0)
        else:
            if os.environ.has_key('USERNAME'):
                value = os.environ['USERNAME']
            elif os.environ.has_key('USER'):
                value = os.environ['USER']
            else:
                value = 'USERNAME'
                


        # Use an MDGModifier so we can undo this work
        #
        self.dgmod = om.MDGModifier()

        # Define a function to do most of the work
        #
        def addMetaData(dependNode, fnDN):
            # Check to see if the attribute already exists on the node
            #
            if fnDN.hasAttribute(name):
                if force:
                    plug = om.MPlug(dependNode, fnDN.attribute(name))
                    self.dgmod.newPlugValueString(plug, value)
                    self.dgmod.doIt()
                else:
                    print ('passing over "' + fnDN.name()+ '": force flag not set to True')
            else:
                # Create a new attribute 
                #
                fnAttr = om.MFnTypedAttribute()
                newAttr = fnAttr.create(name, name, om.MFnData.kString)

                # Now add the new attribute to the current dependency node,
                # using dgmod to facilitate undo
                #
                self.dgmod.addAttribute(dependNode, newAttr)
                self.dgmod.doIt()

                # Create a plug to set and retrieve value off the node.
                #
                plug = om.MPlug(dependNode, newAttr)
                
                # Set the value for the plug, using dgmod to facilitate undo
                #
                self.dgmod.newPlugValueString(plug, value)
                self.dgmod.doIt()


        # Iterate over all dependency nodes in list
        # add the meta-data attribute if it is not already there
        #
        for i in range(selList.length()):
            # Get the dependency node and create
            # a function set for it
            #
            try:
                dependNode = selList.getDependNode(i)
                fnDN = om.MFnDependencyNode(dependNode)
            except RuntimeError:
                om.MGlobal.displayWarning('item %d is not a depend node'%i)
                continue
            addMetaData(dependNode, fnDN)

    def redoIt(self):
        self.dgmod.doIt()

    def undoIt(self):
        self.dgmod.undoIt()

    def isUndoable(self):
        return True

def initializePlugin(plugin):
    pluginFn = om.MFnPlugin(plugin)
    pluginFn.registerCommand(
        PyMetaDataCmd.cmdName, PyMetaDataCmd.creator, PyMetaDataCmd.createSyntax
    )

def uninitializePlugin(plugin):
    pluginFn = om.MFnPlugin(plugin)
    pluginFn.deregisterCommand(PyMetaDataCmd.cmdName)

#-
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