Addattribute / Connectable

Maya
1

Hello,

I'd like to use the addAttribute command to create a float attribute connectable to a shader.

In C++, I do that with :

CODE
static MObject aZeroValue;
      MFnNumericAttribute nAttr;
      aZeroValue = nAttr.create("zeroValue", "zv", MFnNumericData::kFloat);
      nAttr.setConnectable(true);     // default value anyway...
      nAttr.setDefault(0.0f);

So I get a float field, with on the right side a map button.
I thought it was thanks to the setConnectable() function.

But how can I do that with the addAttribute command ?
There isn't "connectable" switch, but this attribute is by default set to true.
But there is no button created...

Thanks.