I'm trying to make a simple tree app that accepts a user's input and adds nodes to a tree structure based on the input. I want every node of the tree to be an instance of a general model, called nodes.
An entry has up to two parts: a parent, which is the beginning of the string up to the first parentheses, and a child, which is in parentheses.
For example, let's say a user enters the following:
"animal(cat)"
"animal(dog)"
"dog(golden retriever)"
"organic_life_form(animal)"
This should generate a tree of this structure:
organic_life_form
|
animal
/ \
dog cat
|
golden retriever
I made a mistake defining my 'node' model, but I'm not sure how to fix it.
class Node(models.Model):
name = models.CharField(max_length=200)
parent = models.ForeignKey(Node)
nodes = models.IntegerField(default=0)
def __unicode__(self):
return self.name
Apparently I am not allowed to use another node as my foreign key "parent", as "Node" isn't yet defined. This seems like a pretty basic error, but I still don't understand why one isn't allowed to do this.
Can anyone explain why I am unable to use another "Node" as a foreign key? And if it's a lost cause, what might be a better way of defining the type of structure I want?
Node isn't available within the class definition, as it has not yet been defined. To permit this, Django allows you to use the name as a string in quotes.
However for your underlying problem you should probably look into an existing library like django-mptt.