Node ID

Created by: Durman

Problem statement

While I was working with material node, I realized the necessity of having some unique value for node for possibility of distinguish one node from others. Svercho already has node_id method and node_id function in data structure file.

https://github.com/nortikin/sverchok/blob/210f48b1d0718820ecc549828f4e3bde133f5fec/node_tree.py#L613-L617

https://github.com/nortikin/sverchok/blob/210f48b1d0718820ecc549828f4e3bde133f5fec/data_structure.py#L807-L811

But I don't understand how it works. I have tried a test of method and function and get equal result.

>>> import sverchok
>>> node = D.node_groups['NodeTree'].nodes['Line']
>>> sverchok.data_structure.node_id(node)
Traceback (most recent call last):
  File "<blender_console>", line 1, in <module>
  File "D:\Серегй\ЯндексДиск\3.Свои_проекты\Blender_code\addons\sverchok\data_structure.py", line 775, in node_id
    return node.node_id
  File "D:\Серегй\ЯндексДиск\3.Свои_проекты\Blender_code\addons\sverchok\node_tree.py", line 615, in node_id
    if not self.n_id:
AttributeError: 'SvLineNodeMK3' object has no attribute 'n_id'

Actually I thought that all classes type of Node can have class attributes with only bpy.props assigned to them. Well I don't see how this code can work.

Related issues: #166 (closed) #116 (closed)