Fields

The form contains the following fields:

• target -- a ModelChoiceField for selecting the target node for the node movement.

  Target nodes will be displayed as a single <select> with its size attribute set, so the user can scroll through the target nodes without having to open the dropdown list first. The select's options will show the tree structure of the valid target nodes like so:

  Root 1
  --- Child 1.1
  ------ Child 1.1.1
  Root 2
  --- Child 2.1
  --- Child 2.2
  

• position -- a ChoiceField for selecting the position of the node movement, related to the target node.

  Its options correspond to the valid values for the position argument for the move_to method Django MTTP adds to model instances.

Construction

Required arguments:

node

When constructing the form, the model instance representing the node to be moved must be passed as the first argument.

Optional arguments:

valid_targets

If provided, this keyword argument will define the list of nodes which are valid for selection in form. Otherwise, any instance of the same model class as the node being moved will be available for selection, apart from the node itself and any of its descendants.

For example, if you want to restrict the node to moving within its own tree, pass a QuerySet containing everything in the node's tree except itself and its descendants (to prevent invalid moves) and the root node (as a user could choose to make the node a sibling of the root node).

target_select_size

If provided, this keyword argument will be used to set the size of the select used for the target node. Defaults to 10.

save() method

When the form's save() method is called, it will attempt to perform the node movement as specified in the form.

If an invalid move is attempted, an error message will be added to the form's non-field errors (accessible using {{ form.non_field_errors }} in templates) and the associated mptt.exceptions.InvalidMove will be re-raised.

It's recommended that you attempt to catch this error and, if caught, allow your view to to fall through to rendering the form again again, so the error message is displayed to the user.

Example usage

A sample view which shows basic usage of the form is provided below:

from django.http import HttpResponseRedirect
from django.shortcuts import render_to_response

from faqs.models import Category
from mptt.exceptions import InvalidMove
from mptt.forms import MoveNodeForm

def move_category(request, category_pk):
    category = get_object_or_404(Category, pk=category_pk)
    if request.method == 'POST':
        form = MoveNodeForm(category, request.POST)
        if form.is_valid():
            try:
                category = form.save()
                return HttpResponseRedirect(category.get_absolute_url())
            except InvalidMove:
                pass
    else:
        form = MoveNodeForm(category)

    return render_to_response('faqs/move_category.html', {
        'form': form,
        'category': category,
        'category_tree': Category.tree.all(),
    })