Mfncompoundattribute

[videohead]

Just a brief question. I would like to create a compound attribute consiting of different data types. Can MFnCompoundAttribute be used to do this?

Thanks

• VH -

[deane]

Yes. Create the children attributes to be whatever complex types you want, but don't call addAttribute for them. Now create the parent attribute using MFnCompoundAttribute and add each of the children to it with an addChild call. Once the children have all been added, use addAttribute to add the parent to your node and the children will automatically be added with it.

The example below creates an array attribute called configuration. Each element of the array is a compound containing a string variable name and a value:

CODE
MFnCompoundAttribute cAttr;
MFnNumericAttribute nAttr;
MFnTypedAttribute tAttr;

aVariable = tAttr.create("variable", "var", MFnData::kString);
aValue = nAttr.create("value", "val", MFnNumericData::kDouble);

aConfiguration = cAttr.create("configuration", "conf");
cAttr.setArray(true);
cAttr.addChild(aVariable);
cAttr.addChild(aValue);
addAttribute(aConfiguration);

Note that if the compound you want to create is an XYZ point or an RGB colour then MFnNumericAttribute provides convenience methods for doing it in a single call.

[videohead]

Thanks deane, you rock!

[videohead]

'Still having trouble creating a compound attribute. Here's a snip of my code:

CODE
MObject parent;
MObject child1;
MObject child2;

MFnNumericAttribute numAttr;

child1 = numAttr.create("child2Attr", "ch1", MFnNumericData::kShort);
child2 = numAttr.create("child1Attr", "ch2", MFnNumericData::k3Double);

MFnCompoundAttribute compAttr;
parent = compAttr.create("parentAttr", "pat");

compAttr.setArray(true);
compAttr.addChild(child1);
compAttr.addChild(child2);

addAttribute(parent );

Oddly, although the compound attribute frame (titled "parentAttr") appears inside the "Extra Attributes" frame in the attribute editor, its child attributes ("child1", and "child2") do not appear inside the the "parentAttr" frame not do they appear elsewhere). Which is perticularly strange because when I type

CODE
listAttr myNode

I get CODE
... parentAttr parentAttr.child2Attr parentAttr.child1Attr parentAttr.child1Attr0 parentAttr.child1Attr1 parentAttr.child1Attr2 ...

as expected.

Further more, I even added the line CODE
cout << compAttr.numChildren() << endl;

to my initilalize() function, and got 2 (again as expected) -- yet the child attributes do not show up in the attribute editor.

Someone please help.

Thanks