Awesome Nested Set Cheat Sheet

Put a new thing inside this root node: physics = Category.create!(:name => ‘Physics’) physics.move_to_child_of(science)

Put another inside this “physics” node: gravity = Category.create!(:name => ‘Gravity’) gravity.move_to_child_of(physics)

Now you should have something that resembles this: + science |__ physics |____ gravity

Accessing the data:

Class methods:
`Category.root`	the first root node
`Category.roots`	all root nodes
Instance methods
`my_cat.root`	root for this node.
`my_cat.level`	the level of this object in the tree. root = 0
`my_cat.parent`	the node’s immediate parent
`my_cat.children`	array of immediate children (just those in the next level).
`my_cat.ancestors`	array of all parents, parents’ parents, etc, excluding self.
`my_cat.self_and_ancestors`	array of all parents, parents’ parents, etc, including self.
`my_cat.siblings`	array of brothers and sisters (all at that level), excluding self.
`my_cat.self_and_siblings`	array of brothers and sisters (all at that level), including self.
`my_cat.descendants`	array of all children, childrens’ children, etc., excluding self.
`my_cat.self_and_descendants`	array of all children, childrens’ children, etc., including self.
`my_cat.leaves`	array of all descendants that have no children.
Instance methods: Tests	(these don’t need to hit the DB to respond)
`my_cat.root?`	true if this is a root node
`my_cat.child?`	true if this is a child node. It has a parent.
`my_cat.is_ancestor_of?(obj)`	true if nested by any obj
`my_cat.is_or_is_ancestor_of?(obj)`	true if nested by any obj or self is obj
`my_cat.is_descendent_of?(obj)`	true if self is nested under obj
`my_cat.is_or_is_descendent_of?(obj)`	true if self is nested under obj or self is obj
`my_cat.leaf?`	true if this is a leaf node. It has no children.

Last edited by robotofthefuture, Tue Aug 04 19:56:46 -0700 2009

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