Graph models
============

:synopsis: Renders a graphical overview of your project or specified apps.

Creates a GraphViz_ dot file for the specified app names based on their models.py.
You can pass multiple app names and they will all be combined into a single model.
Output is usually directed to a dot file.

Several options are available: grouping models, including inheritance,
excluding models and columns, and changing the layout when rendering to an output
image.

With the latest revisions it's also possible to specify an output file if
pygraphviz_ is installed and render directly to an image or other supported
file-type.


Selecting a library
-------------------

You need to select the library to generate the image. You can do so by passing
the --pygraphviz or --pydot parameter, depending on which library you want to use.

When neither of the command line parameters are given the default is to try and load
pygraphviz or pydot (in that order) to generate the image.

To install pygraphviz you usually need to run this command::

  $ pip install pygraphviz

It is possible you can't install it because it needs some C extensions to build. In
that case you can try other methods to install or you can use PyDot.

To install pydot you need to run this command::

  $ pip install pyparsing==1.5.7
  $ pip install pydot

Installation should be fast and easy. Remember to install this exact version of
pyparsing, otherwise it's possible you get this error:

    Couldn't import dot_parser, loading of dot files will not be possible.


Default Settings
----------------

The option GRAPH_MODELS = {} can be used in the settings file to specify default options::

  GRAPH_MODELS = {
    'all_applications': True,
    'group_models': True,
  }

It uses the same names as on the command line only with the leading two dashes removed and
the other dashes replaced by underscores.


Templates
---------

Django templates are used to generate the dot code. This in turn can be drawn into a image
by libraries like *pygraphviz* or *pydot*. You can extend or override the templates if needed.

Templates used:

 - django_extensions/graph_models/digraph.dot
 - django_extensions/graph_models/label.dot
 - django_extensions/graph_models/relation.dot

Documentation on how to create dot files can be found here: http://www.graphviz.org/Documentation.php

.. warning::
  Modifying Django's default templates behaviour might break *graph_models*

  Please be aware that if you use any *template_loaders* or extensions that change the
  way templates are rendered that this can cause *graph_models* to fail.

  An example of this is
  the Django app *django-template-minifier* this automatically removed the newlines before/after
  template tags even for none-html templates which leads to a mallformed file.

Example Usage
-------------

With *django-extensions* installed you can create a dot-file or an
image by using the *graph_models* command::

  # Create a dot file
  $ ./manage.py graph_models -a > my_project.dot

::

  # Create a PNG image file called my_project_visualized.png with application grouping
  $ ./manage.py graph_models -a -g -o my_project_visualized.png

  # Same example but with explicit selection of pygraphviz or pydot
  $ ./manage.py graph_models --pygraphviz -a -g -o my_project_visualized.png
  $ ./manage.py graph_models --pydot -a -g -o my_project_visualized.png

::

  # Create a dot file for only the 'foo' and 'bar' applications of your project
  $ ./manage.py graph_models foo bar > my_project.dot


.. _GraphViz: http://www.graphviz.org/
.. _pygraphviz: https://pygraphviz.github.io/
.. _pydot: https://pypi.python.org/pypi/pydot
