mptt.utils module contains the following functions for working
with and creating lists of model instances which represent trees.
Creates an iterator which returns (previous, current, next) triples,
None filling in when there is no previous or next available.
This function is useful if you want to step through a tree one item at a time and you need to refer to the previous or next item in the tree. It is used in the implementation of tree_item_iterator().
- A list or other iterable item.
This function is used to implement the
tree_info template filter,
yielding two-tuples of (tree item, tree structure information
tree_info documentation for more information.
- A list or iterable of model instances which represent a tree.
- Boolean. If
True, a list of unicode representations of the ancestors of the current node, in descending order (root node first, immediate parent last), will be added to the tree structure information
dict` under the key ``'ancestors'.
This function is used in the implementation of the
drilldown_tree_for_node template tag.
It creates an iterable which yields model instances representing a drilldown tree for a given node.
A drilldown tree consists of a node’s ancestors, itself and its immediate children or all descendants, all in tree order.
Optional arguments may be given to specify details of a relationship between the given node’s class and another model class, for the purpose of adding related item counts to the node’s children.
- A model instance which represents a node in a tree.
- A model class which has a relationship to the node’s class.
- The name of the field in
rel_clswhich holds the relationship to the node’s class.
- The name of an attribute which should be added to each child of the
node in the drilldown tree (if any), containing a count of how many
rel_clsare related to it through
True, the count will be for items related to the child node and all of its descendants. Defaults to
Takes a list/queryset of model objects in MPTT left (depth-first) order and caches the children and parent on each node. This allows up and down traversal through the tree without the need for further queries. Use cases include using a recursively included template or arbitrarily traversing trees.
Returns a list of top-level nodes. If a single tree was provided in its entirety, the list will of course consist of just the tree’s root node.
Aliases to this function are also available:
- Use for recursive rendering in templates.
- Useful for chaining with queries; e.g., Node.objects.filter(**kwargs).get_cached_trees()
- An iterable that consists of all nodes which are to be cached.