Hi all! Happy new year!
Sorry for my bad english.
On this weekend I reviewed app-loading branch[1] and want to propose some
improvements.
Now app-loading branch resolve how to load application, store its meta data
and load its models.
I plan to extend it to get simple way for replacing the same type
applications. This problem is
know as Lazy Foreign Key and now can be resolve through settings, but django
contrib modules
currently is not supported it. I propose more beautiful way to resolve this
problem.
The main goal of my improvements is adding ability to simple replace one
application to another
with the same type but another functionality. For example, if you need
replace `django.contrib.auth`
on your own application you must rewrite all used 3rd-party applications
linked with it now. I
propose way to resolve this problem and I think It is not hard to implement
with saving backward
compatibilities.
1. Change INSTALLED_APPS form tuple to dictionary or may be it's better to
use something with
the same interface as tuple and dictionary
INSTALLED_APPS = {
'auth': 'django.contrib.auth',
'comments': 'django.contrib.comments'.
...
}
For backward compatibility it checks on setting load stage and convert to
dictionary if it need.
INSTALLED_APPS will be low level API to install applications. I propose
install application through
`install_applications` function like this:
from django.core.apps import install_applications
INSTALLED_APPS = install_applications(
'django.contrib.contenttypes',
'django.contrib.sessions',
...
auth = 'django.contrib.auth',
comments = 'django.contrib.comments'
gallery = App(path='my_gallery', db_prefix='new_gallery',
verbose_name=u'My new gallery')
)
There are args and kwargs passed to `install_applications`. It can be python
module names of
django applications. Keys of kwargs are system names of the installed
applications. This names
will be used to get application instance in other applications (see next for
more details).
For applications passed through args keys will be auto generated.
The main benefit is a manage installed applications in project settings
module without make
changes in this applications.
Application loading process will be as listed below:
* iterate over INSTALLED_APPS items
* if item is string - try to load application definition
(`Application`class) from python package
defined in this string and create its instance. If application
definition is not provided, it will be
auto generated. `django.core.apps.App` class will be used for it.
* if item is `App` instance, check existence of python package at `path`
attribute of `App` instance
and `ImproperlyConfigured` exception will be raised if this python
package is not installed.
2. Way to organize relations between models of different applications
(something like this it
already exist in app-loading branch and trunk. I show this only for example
and demonstrate
syntax)
from django.core.apps import get_app, get_model
auth = get_app('auth')
class MyModel(models.Model):
user = models.ForeignKey(auth.models.User)
or
class MyModel(models.Model):
user = models.ForeignKey(get_model('auth.User'))
3. Add new exceptions: `AppIsNotInstalled` (instead of
`ImproperlyConfigured`) will be raised if it is
try to load not installed applications through `get_app`.
[1] http://code.djangoproject.com/wiki/SummerOfCode2010#Apploading
Waiting for your comments.
Cheers!
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