Dynamic Types

This document explains the system for extending the models that ship with Courant News by default. It allows for the addition and grouping of fields to create new virtual model types that can be accessed through the template system and through the admin interface.

Introduction

Courant News comes with a number of built-in models, which are often designed as a core/common subset of functionality as required by most news organizations. However, in many cases, news organizations will require additional data fields on some of these types.

In accordance with the Courant News philosophy of not requiring modifications to the core platform, as well as that of not requiring coding wherever possible, the dynamic model system allows site operators to create and manage their dynamic types through the admin interface; no coding, and no server restarts required.

Dynamic Types

class models.DynamicType

While the ability to add additional data fields to, for example, the Article model, some of those fields may only be applicable to certain groups of articles, and others to other groups of articles. As a result, multiple DynamicTypes can be associated with any given base model (Article, in this example) representing such groupings.

Dynamic Type Fields

class models.DynamicTypeField

Courant News currently supports four types of dynamic type fields: booleans (true/false values), integers, short text fields (less than 255 characters), and long text fields (no length limits). More types will be added in the future, but the decision of which types to implement will be driven by community feedback (so speak up on the mailing list!).

Integration with Get Tag

This feature integrates with the get tag, which means that any DynamicType definitions can be specified as the model in a get tag call. See the documentation for that feature for further information.

Technical Overview

Behind the scenes, this feature uses an Entity-Attribute-Value system to store the data.

This means that an extra query is required when accessing dynamic fields on a model, although after the first time such a field is accessed for a particular model instance, all the dynamic fields for that instance’s dynamic type are retrieved and cached. As a result, the ‘cost’ of retreiving these dynamic fields is only incurred if one of them is used, and it is only paid once per instance.