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models.py with django_dag models for parts hierarchy

This is a portion of my code for creating a hierarchical relation between assemblies, subparts, and parts and so forth (although really, everything is a Part) The project being used is [django_dag](https://github.com/elpaso/django-dag) For the sake of example, let's use this structure: * Bike 1 * - Front Tire & Back Tire combo 000 * - - Front Tire 000 * - - Rear Tire 000 * - Frame 000 * - Gearset type 000 * - - Crank 000 * - - Rear Cassette 000 * . * Bike 2 * - Front Tire & Back Tire combo 001 * - - Front Tire 001 * - - Rear Tire 000 * - Frame 001 * - Gearset type 000 * - - Crank 000 * - - Rear Cassette 000 Using the above example, I couldn't use a MPTT structure because Gearset 000 is used in 2 different parents (bike 1 and bike 2). So I had to use the DAG [(wiki)](http://en.wikipedia.org/wiki/Directed_acyclic_graph) structure which allows multiple parents. The `Relationship` model holds the dag information, mainly a parent and child field. (Tire combo 001 is child of Bike2, front tire 001 is child of tire combo 001, etc) After get the dag structure using the `ancestors_tree` method on a Part object, I search for the BillOfMaterial info for that whole tree. In my case the Bill Of Material info is unique per assembly, so that's why there are seperate models. It becomes a bit of a pain to have to save/delete both the relationship and BoM models at the same time, and to check if one exists to create the other etc. But I've made my first 'hack' through it to have a function project, and am ready to make some revisions now.

  • models
  • hierarchy
  • dhango_dag
  • django-dag
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Dynamically add css-classes to formfields

This example assumes you have a form and want to highlight one of two fields by setting <class="highlight"> in the html dynamically. This is an alternative to <https://docs.djangoproject.com/en/1.3/ref/forms/widgets/#customizing-widget-instances>, but now you're not limited to assigning the class to the fields html-output, instead you can also assign it to a div around the field like done here. After assigning a css-attribute to a field, we access the css via a templatefilter *{{ field|css }}* that looks up *field.form.fields[field.name].css* and not simply *field.css*, since the latter would try to access a non-existing css-attribute on a BoundField-instance EDIT: The templatefilter is unnecessary. There is a much easier way, since the original field itself is an attribute of the BoundField named 'field'. So in the template, we can access the css via {{ field.field.css }}. Thanks to Tom Evans for pointing me at this.

  • css
  • form
  • class
  • dynamic-form
  • formfield
  • dynamic-css
  • css-class
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PropertyBasedContext

This approach allows you to avoid code duplication to produce same context data for different views. It could be usefull when you are using templates inheritace.

  • context
  • contextprocessor
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Template loader to target a specific template

This is http://djangosnippets.org/snippets/1376/ rewritten as a new class-style Loader, and slightly improved. Allows you to reference templates like this: app_label:some/template/name.html This makes it possible to insert customizations at any point in a template hierarchy. For example, you could replace a block within the base admin template: {% extends "admin:admin/base.html" %} {% block breadcrumbs %}Custom Breadcrumbs-Style{% endblock %}

  • templates
  • loader
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tag to store a settings value as template variable

Get any value from settings.py as a template variable. The variable can then be used in conditional tags. E.g. to show a link to a help page only if it the help page url is defined in settings.py {% load get_setting %} {% get_setting MY_HELP_URL as help_url %} {% if help_url %}<a href="{% help_url|safe %}">Help</a>{% endif %}

  • template
  • tag
  • templatetag
  • settings
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Enable AWS ELB with SSL Termination

When using Amazon's ELB with SSL termination, Django needs to know that the requests are secure. You need to use the special indication given on the request (HTTP_X_FORWARDED_PROTO) to determine that. This middleware will do that for you. The second part is forcing requests to HTTPS in case they are not. This part is not mandatory and could probably be done using configuration rules in your HTTP server. Note that I did it for the specific site, simply to avoid redirecting requests which are not of interest in the first place. This snippet is based on work done in [Django-Heroism](https://github.com/rossdakin/django-heroism).

  • SSL
  • Middleware
  • AWS
  • Cloud
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Automatic slug generation signal

A pre_save signal that will automatically generate a slug for your model based on the "title" attribute, and will store the new slug in the "slug" attribute. USAGE: from django.db.models.signals import pre_save from YOURPACKAGE import slug_generator pre_save.connect(slug_generator, sender=YOURMODEL)

  • slug
  • slugify
  • automatic
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Spanish National Identification Number Field (DNI)

This django field can be used to introduce Spanish national Identification Numbers (NIF). It validates the NIF format and checks if the last letter is correct. It also validates NIE numbers for foreign people. You can use the field in your own forms: 'code' dni = DNIField(max_length=15, widget=forms.TextInput(), label=_('DNI')) 'code'

  • validation
  • dni
  • custom fields
  • nif
  • nid
  • nie
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Simple Django event calendar template tag

I wanted a simple way to display events for a given month in a calendar, so I adapted some code to write a template tag. `Event` is the model class, and it needs to have a `date_and_time` field. Each event is part of a `Series`, so in the view you can filter events by which series, or display events for all known Series. [Full explanation and description of simple Django event calendar template tag](http://williamjohnbert.com/2011/06/django-event-calendar-for-a-django-beginner/).

  • calendar
  • event-calendar
  • htmlcalendar
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Edit users on Group admin

Ordinarily, it is not possible to edit Group membership from the Group admin because the m2m relationship is defined on User. With a custom form, it is possible to add a ModelMultipleChoiceField for this purpose. The trick is to populate the initial value for the form field and save the form data properly. One of the gotchas I found was that the admin framework saves ModelForms with commit=False and uses the save_m2m method when the group is finally saved. In order to preserve this functionality, I wrap the save_m2m method when commit=False.

  • admin
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