View Full Version : Properly handling Inheritance of VizNode and using copy

09-05-2012, 09:58 AM
Hello Vizard support.

I had a question on how to properly implement the <viz.VizNode>.copy method when using inheritance.

I have created several class that inherit from VizNode, however they have their own __init__ functions that take in additional parameters beyond what VizNode might utilize.

When I create a copy of these objects using the original copy method provided by Vizard, I get an error that indicates I am not getting the correct number of parameters into the class __init__ method I created.

When I looked at how copy was implemented, it looks like you return an instance of self.__class__(Vizard Stuff In Here) when I call copy.

Below is my __init__ method, as you can see I take in an additional template parameter.

class GreenObject(Model3D, Properties):
def __init__(self, modelString, GOTemplate):
Model3D.__init__(self, modelString)

self.publicVariables = []

self.variableValues = [0.0] * len(GreenObject.properties2Indices)

self.greenObjectTemplate = GOTemplate

If possible, I would like to call the original copy functionality along with doing some copying of my own when <*>.copy is called.

Normally, I would just call the base classes version then add my own code. But I don't know much about what VizNode is doing behind the scenes and I figured you'd have a better idea on how to handle this.


09-05-2012, 11:55 AM
Your example code does not show how the node object is created. Is it passed to your class, or is it created within the __init__ of your class?

09-05-2012, 12:17 PM
Sorry, forgot to include that class as well.
Here is a super class of GreenObject called Model3D which derives
from viz.VizNode

class Model3D(viz.VizNode):

GORM = None

def __init__(self, string):

#Typical string entry
if type(string) == str:
base = viz.add(string)
viz.VizNode.__init__(self, base.id)

#Use for on-the-fly creation in Vizard
elif isinstance(string, viz.VizNode):
base = string
viz.VizNode.__init__(self, base.id)

elif isinstance(string, int): #We are dealing with a copy that has passed in an id number
viz.VizNode.__init__(self, string)

print 'Copy type', string, type(string)

09-05-2012, 02:12 PM
The node.copy command will pass all extra keyword arguments to the class __init__ method. You can override the copy method in your class and have it pass all the required arguments as keyword arguments to the underlying node.copy method. Example:import viz

class MyNode(viz.VizNode):

def __init__(self, model, parameter):

if isinstance(model,basestring):
base = viz.add(model)
viz.VizNode.__init__(self, base.id)

elif isinstance(model, viz.VizNode):
viz.VizNode.__init__(self, model.id)

elif isinstance(model, int):
viz.VizNode.__init__(self, model)

self._parameter = parameter

def copy(self, parameter):
return viz.VizNode.copy(self,parameter=parameter)

node = MyNode('gallery.osgb',0)
nodeCopy = node.copy(1)

Does this work for you scenario?

09-06-2012, 06:56 AM
I believe it will work.
I'll create a new instance of the class in the copy constructor and pass the copy into the initializer.

This way the copy command will now not just copy viz.VizNode but I can code it to also copy the rest of the parameters I've attached to my new class as well.

Thank you,