django-multilingualfield 0.3.1

# django-multilingualfield #

## About ##

A [south](http://south.aeracode.org/)-compatible suite of django fields that make it easy to manage multiple translations of text-based content (including files/images).

### Current Version ###

0.3

## Installation ##

Installation is easy with [pip](https://pypi.python.org/pypi/pip):

```bash
$ pip install django-multilingualfield
```

### Requirements ###

`django-multilingualfield` will install the following dependencies:

* `django-classy-tags` >= 0.3.4.1
* `lxml` >= 3.1.2

### Settings ###

To use `django-multilingualfield`, first add `multilingualfield` to `INSTALLED_APPS`:

```python
INSTALLED_APPS += ('multilingualfield')
```

Secondly, make sure that [`LANGUAGES`](https://docs.djangoproject.com/en/dev/ref/settings/#languages) is properly defined in your settings file.

If you don't have [`LANGUAGE_CODE`](https://docs.djangoproject.com/en/dev/ref/settings/#language-code) set in your settings file it will default to 'en-us' (U.S. English). It is recommended you manually set [`LANGUAGE_CODE`](https://docs.djangoproject.com/en/dev/ref/settings/#language-code) (even if you are keeping the default value of 'en-us') *IN ADDITION TO* adding an entry for that language code (as the _first_ language) in [`LANGUAGES`](https://docs.djangoproject.com/en/dev/ref/settings/#languages). Here's an example:

```python
LANGUAGE_CODE = 'en'

LANGUAGES = [
('en', 'English'),
('es', 'Español') # See note below note
]
```
> #### NOTE ####
> `ñ` is the UTF8 encoding for 'ñ'

If you'd like to use MultiLingual* fields in templates you'll need django's `'django.middleware.locale.LocalMiddleware'` added to your [`MIDDLEWARE_CLASSES`](https://docs.djangoproject.com/en/dev/ref/settings/#std:setting-MIDDLEWARE_CLASSES) setting and `'django.core.context_processors.i18n'` added to your [`TEMPLATE_CONTEXT_PROCESSORS`](https://docs.djangoproject.com/en/dev/ref/settings/#std:setting-TEMPLATE_CONTEXT_PROCESSORS) setting:

```python
MIDDLEWARE_CLASSES += (
'django.middleware.locale.LocaleMiddleware',
)

TEMPLATE_CONTEXT_PROCESSORS += (
'django.core.context_processors.i18n',
)
```

> #### NOTE ####
> django-multilingualfield uses [`django.utils.translation.get_language`](https://docs.djangoproject.com/en/dev/ref/utils/#django.utils.translation.get_language) to determine which translation to serve by default.
> To better understand how Django determines language preference read the aptly titled ['How Django discovers language preference'](https://docs.djangoproject.com/en/dev/topics/i18n/translation/#how-django-discovers-language-preference) section from the i18n topic page within the official django documentation.

## Overview ##

django has [excellent translation tools](https://docs.djangoproject.com/en/dev/topics/i18n/translation/) but a recent project at WGBH required manually-written translations for nearly all text & image content served by the site.

I didn't want to create multiple `CharField`, `TextField` or `ImageField` attributes for each field that needed translations (i.e. 'title_en' and 'title_es') for multiple reasons:

1. They'd be a giant pain to keep track of.
2. Templates and/or views would be polluted with alot of crufty if/else statements.
3. The site needed to launch with support for English and Spanish but I figured new languages would be added down the road and wanted to make any future additions as smooth as possible.

### Available Fields ###

`django-multilingualfield` contains three fields ready-for-use in your django project.

1. `multilingualfield.fields.MultiLingualCharField`: Functionality mirrors that of django's `django.db.models.CharField`
2. `multilingualfield.fields.MultiLingualTextField`: Functionality mirrors that of django's `django.db.models.TextField`
2. `multilingualfield.fields.MultiLingualFileField`: Functionality mirrors that of django's `django.db.models.FileField`

At the database level, `MultiLingualCharField`, `MultiLingualTextField` and `MultiLingualFileField` are essentially identical in that their content is stored within 'text' columns (as opposed to either 'varchar' or 'text'); they diverge only in the widgets/forms they use.

Any options you would pass to a `CharField`, `TextField` or `FileField` (i.e. `blank=True`, `max_length=50`, `upload_to='path/'`, `storage=StorageClass()`) will work as expected but `max_length` **will not be enforced at a database level** (only during form creation and input validation).

## Examples ##

### Model Example ###

Use `MultiLingualCharField`, `MultiLingualTextField` and `MultiLingualFileField` just like you would any django field:

```python
from django.db import models

from multilingualfield import fields as mlf_fields

class TestModel(models.Model):
title = mlf_fields.MultiLingualCharField(
max_length=180
)
short_description = mlf_fields.MultiLingualCharField(
max_length=300
)
long_description = mlf_fields.MultiLingualTextField(
blank=True,
null=True
)
image = mlf_fields.MultiLingualFileField(
upload_to='images/',
blank=True,
null=True
)
```

`django-multilingualfield` is fully integrated with [south](http://south.aeracode.org/) so migrate to your heart's content!

#### What's Stored In The Database ####

If `LANGUAGES` is set in your project's settings like this...

```python
LANGUAGES = [
('en', 'English'),
('es', 'Español')
]
```

...then `django-multilingualfield` will store translations for a piece of text in a single 'text' db column as XML in the following structure:

```xml
<languages>
<language code="en">
Hello
</language>
<language code="es">
Hola
</language>
</languages>
```
> ##### NOTE #####
> The example above includes whitespace for readability, the final value stored in the database will have all between-tag whitespace removed.

#### What's Served By The Application ####

Even though `MultiLingualCharField` and `MultiLingualTextField` instances are stored in the database as XML they are served to the application as a python object. The above block of XML would return an instance of `multilingualfield.fields.MultiLingualText` with two attributes:

* `en` (with a value of `u'Hello'`)
* `es` (with a value of `u'Hola'`)

The translation corresponding to the current language of the active thread (as determined by calling [`django.utils.translation.get_language`](https://docs.djangoproject.com/en/dev/ref/utils/#django.utils.translation.get_language)) will be returned by directly accessing the field.

#### Creating Instances in the Shell ####

Let's create an instance of our above example model (`TestModel`) in the python shell:

```bash
$ python manage.py shell
```

```python
>>> from testapp.models import TestModel
>>> from multilingualfield.datastructures import MultiLingualText
>>> title = MultiLingualText()
>>> title.en = 'Hello'
>>> title.es = 'Hola'
>>> x = TestModel(title=title)
>>> x.save()
>>> x.title.en
u'Hello'
>>> x.title.es
u'Hola'
>>> x.title
u'Hello'
>>> from django.utils.translation import get_language, activate
>>> get_language()
'en-us'
# NOTE: 'en-us' will ALWAYS be the current language in the active
# thread when you load the python shell via manage.py. To learn why
# visit: https://code.djangoproject.com/ticket/12131#comment:6
>>> activate('en')
>>> get_language()
'en'
>>> activate('es')
>>> get_language()
'es'
>>> x.title
u'Hola'
>>> activate('en')
>>> x.title
'en'
```

### Admin Integration ###

Both `MultiLingualCharField` and `MultiLingualTextField` are admin-ready and will provide either a `TextInput` (for `MultiLingualCharField` instances) or `Textarea` (for `MultiLingualTextField` instances) field for each language listed in `settings.LANGUAGES`.

#### Improved Admin Styling ####

The default formfields for MultiLingual* fields do not include admin-friendly styling so if you want them to look pretty within the admin you have a few options:

1. Swap-out `admin.ModelAdmin` for `MultiLingualFieldModelAdmin` in your admin configs for models that have MultiLingual* fields:

```python
# testapp.admin
from django.contrib import admin

from multilingualfield.admin import MultiLingualFieldModelAdmin

from .models import TestModel


class TestModelAdmin(MultiLingualFieldModelAdmin):
"""
Adds admin-friendly styling to all MultiLingual* fields
for TestModel within the admin
"""
list_display = ('title',)

admin.site.register(TestModel, TestModelAdmin)
```

2. Manually specify MultiLingual* widgets with [`formfield_overrides`](https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.formfield_overrides):

```python
# testapp.admin
from django.contrib import admin

from multilingualfield import widgets as mlf_widgets
from multilingualfield import fields as mlf_fields

from .models import TestModel


class TestModelAdmin(admin.ModelAdmin):
"""
Adds admin-friendly styling to all MultiLingual* fields
for TestModel via formfield_overrides
"""
list_display = ('title',)
formfield_overrides = {
mlf_fields.MultiLingualCharField: {
'widget': mlf_widgets.MultiLingualCharFieldDjangoAdminWidget
},
mlf_fields.MultiLingualTextField: {
'widget': mlf_widgets.MultiLingualTextFieldDjangoAdminWidget
},
}

admin.site.register(TestModel, TestModelAdmin)
```

3. Manually specify MultiLingual* widgets on a ModelForm subclass:

```python
# testapp.forms
from django.forms.models import ModelForm

from multilingualfield import widgets as mlf_widgets

from .models import TestModel


class TestModelForm(ModelForm):

class Meta:
model = TestModel
fields=(
'title',
'short_description',
'long_description'
)
widgets = {
'title': mlf_widgets.MultiLingualCharFieldDjangoAdminWidget,
'short_description': mlf_widgets.MultiLingualCharFieldDjangoAdminWidget,
'long_description': mlf_widgets.MultiLingualTextFieldDjangoAdminWidget
}
```

Integrating the custom form into your admin configuration:

```python
# testapp.admin
from django.contrib import admin

from .forms import TestModelForm
from .models import TestModel


class TestModelAdmin(admin.ModelAdmin):
"""
Adds admin-friendly styling to all MultiLingual* fields
via a custom form
"""
form = TestModelForm

admin.site.register(TestModel, TestModelAdmin)
```

### Template Example ###

Template usage is simple & straight forward, here's an example template for how you might render a instance of `TestModel`:

```python
{% load i18n %}
<html>
<head>
<title>{{ object.title }}</title>
</head>
<body>
<h1>{{ object.title }}</h2>
<p>{{ object.short_description }}</p>
{% if object.long_description %}
{{ object.long_description }}
{% else %}
{% trans 'No long description provided' %}
{% endif %}
</body>
</html>
```

> #### NOTE ####
> For more information about the `trans` templatetag used in the example above check out the [django docs](https://docs.djangoproject.com/en/dev/topics/i18n/translation/#trans-template-tag).

The example above is typical for most use cases (when you want to render values associated with the user's current language thread) but you always have access to the language-specific attributes:

```html
{% load i18n %}
<html>
<head>
<title>{{ object.title }}</title>
</head>
<body>
<h1>{{ object.title }}</h2>
<!-- Forcing the English display of object.title -->
<h2>{% trans 'Title (English)' %}: {{ object.title.en }}</h2>

<!-- Forcing the Spanish display of object.title -->
<h2>{% trans 'Title (Spanish)' %}: {{ object.title.es }}</h2>

<p>{{ object.short_description }}</p>
{% if object.long_description %}
{{ object.long_description }}
{% else %}
{% trans 'No long description provided' %}
{% endif %}
</body>
</html>
```