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django-smarter 1.1

Smarter declarative style generic views for Django.

Another approach for declarative style generic views for Django. I beleive, it's a bit smarter :)

Overview

So many times we have to write:

@login_required
def edit_post(request, pk):
    post = get_object_or_404(Post, pk=pk)
    if request.method == 'POST':
        form = EditPostForm(request.POST, instance=post)
        if form.is_valid():
            post = form.save()
            return redirect(post.get_absolute_url())
    else:
        form = EditPostForm()
    return render(request, 'edit_post.html', {'form': form})

Right? Well, it's ok to write some reusable helpers for such repeatable views, but when we don't need sophisticated ones here we go:

class PostViews(smarter.GenericViews):
    model = Post
    options = {
        'add': {
            'form': NewPostForm,
            'decorators': (login_required,)
        },
        'edit': {
            'form': EditPostForm,
            'decorators': (login_required,)
        },
        'remove': {
            'decorators': (login_required,)
        }
    }

That's it.

Changes in v1.0

API is finally and completely changed since v0.6 release.

We've made a "quantum jump" by breaking old-and-not-so-good API to new one - solid and nice. Hope you'll like it.

Here are some hints that may help you with migration. I'm actually successfully migrated my real-production project, so the hints are based on "real-battle" example.

Contributors

Thank you, comrades! :)

Installation

Requirements:

  • Django >= 1.4

Installation:

pip install django-smarter

You may add smarter to your INSTALLED_APPS to get default templates and tests, but you don't have to:

INSTALLED_APPS = (
    # ...
    'smarter',
    # ...
)

Then you should define your views and include them in URLs, see Getting started section below.

Getting started

Create your models

Let’s define a simple model:

class Page(models.Model):
    owner = models.ForeignKey('auth.User')
    title = models.CharField(max_length=100)
    text = models.TextField()

    def __unicode__(self):
        return self.title

Register views

Now you can add generic views for the model.

In your urls.py:

import smarter
from myapp.models import Page

site = smarter.Site()
site.register(smarter.GenericViews, Page)

urlpatterns = patterns('',
    url(r'^', include(site.urls)),

    # other urls ...
)

This code creates generic views for Page model, accessed by urls:

  • /page/
  • /page/add/
  • /page/<pk>/
  • /page/<pk>/edit/
  • /page/<pk>/remove/

Customize views

Subclass from smarter.GenericViews and set custom options and/or override methods.

from django.contrib.auth.decorators import login_required
import smarter
from .models import Page

class PageViews(smarter.GenericViews):
    model = Page

    options = {
        'add': {
            'decorators': (login_required,)
            'exclude': ('owner',)
        },
    }

    def add__save(self, request, form, **kwargs):
        obj = form.save(commit=False)
        obj.owner = request.user
        obj.save()
        return obj

And don't forget to register new views in urls.py:

import smarter
from myapp.views import PageViews

site = smarter.Site()
site.register(PageViews) # model argument is not required as model is already set in PageViews

urlpatterns = patterns('',
    url(r'^', include(site.urls)),
)

Customize templates

In the example above each URL by default to template.

URL Template Context
/page/ myapp/page/index.html {{ objects_list }}
/page/add/ myapp/page/add.html {{ obj }}, {{ form }}
/page/<pk>/ myapp/page/details.html {{ obj }}
/page/<pk>/edit/ myapp/page/edit.html {{ obj }}, {{ form }}
/page/<pk>/remove/ myapp/page/remove.html {{ obj }}

Default template search paths are:

('%(app)s/%(model)s/%(action)s.html',
 '%(app)s/%(model)s/%(action)s.ajax.html',
 'smarter/%(action)s.html',
 'smarter/_form.html',
 'smarter/_ajax.html',)

So, you have some easy way options:

  1. you may override matching templates
  2. you may set 'template' key in PageViews.options for each action
  3. you may override default search paths by settings new PageViews.defaults (read Options section for details)

Singleton Site

A very special instance of smarter.Site is in the smarter module. It allows you to register your applications' views outside your urls.py file, and works well with autodiscover().

Here is smarter_views.py in your app:

from smarter import site, GenericViews
from models import Model

class Views(GenericViews):
    model = Model

    # ...

site.register(Views)

... And urls.py:

from django.conf.urls import patterns, include, url
import smarter

smarter.autodiscover()
urlpatterns = patterns('',
    url(r'^', include(smarter.site.urls)),
)

This is mostly recommended for non-reusable applications local to your Django project.

API reference

Actions

Actions are actually "ids" for views. Well, each action has id like 'add', 'edit', 'bind-to-user' and is mapped to view method with underscores instead of '-': add, edit, bind_to_user.

In smarter.GenericViews class such actions are defined by default:

Action URL View method Named URL
index / index(request) [prefix]-[model]-index
add /add/ add(request) [prefix]-[model]-add
details /<pk>/ details(request, pk) [prefix]-[model]-details
edit /<pk>/edit/ edit(request, pk) [prefix]-[model]-edit
remove /<pk>/remove/ remove(request, pk) [prefix]-[model]-remove

What is [prefix]? Prefix is defined for smarter.Site instance:

site = smarter.Site(prefix='myapp')
site.register(PageViews)
# ...

So, it can be empty and URL names without prefix are defined as [model]-index. Please, read Reversing urls section for more details.

Options

Options is a GenericViews.options dict, class property, it contains actions names as keys and actions parameters as values. Parameters structure is:

{
    'url':          <string for url pattern>,
    'form':         <form class>,
    'decorators':   <tuple/list of decorators>,
    'fields':       <tuple/list of form fields>,
    'exclude':      <tuple/list of excluded form fields>,
    'initial':      <tuple/list of form fields initialized by request.GET>,
    'permissions':  <tuple/list of required permissions>,
    'widgets':      <dict for widgets overrides>,
    'help_text':    <dict for help texts overrides>,
    'required':     <dict for required fields overrides>,
    'template':     <string template name>,
    'redirect':     <string or callable returning redirect path>
}

Every key here is optional. So, here's how options can be defined for views:

import smarter

class Views(smarter.GenericViews):
    model = <model>

    defaults = <default parameters>

    options = {
        '<action 1>': <parameters 1>,
        '<action 2>': <parameters 2>
    }

And here's GenericViews.defaults class attribute:

defaults = {
    'initial': None,
    'form': ModelForm,
    'exclude': None,
    'fields': None,
    'labels': None,
    'widgets': None,
    'required': None,
    'help_text': None,
    'next': None,
    'template': (
        '%(app)s/%(model)s/%(action)s.html',
        '%(app)s/%(model)s/%(action)s.ajax.html',
        'smarter/%(action)s.html',
        'smarter/_form.html',
        'smarter/_ajax.html',),
    'decorators': None,
    'permissions': None,
}

When option value can't be found in options dict for action it's searched in GenericViews.defaults. Note, that defaults are applied to all actions.

Action names and URLs

Actions are named so they can be mapped to views methods and they should not override reserved attributes and methods, so they:

  1. must contain only latin symbols and '_' or '-', no spaces
  2. can't be in this list: 'model', 'defaults', 'options', 'deny'
  3. can't start with '-', '_' or 'get_'
  4. can't contain '__'

Sure, you'll get an exception if something goes wrong with that. We're following 'errors should never pass silently' here.

And here's how URLs for default views are defined:

{
    'index': {
        'url': r'',
    },
    'details': {
        'url': r'(?P<pk>\d+)/',
    },
    'add': {
        'url': r'add/',
    },
    'edit': {
        'url': r'(?P<pk>\d+)/edit/',
    },
    'remove': {
        'url': r'(?P<pk>\d+)/remove/',
    }
}

smarter.Site

Site(prefix=None, delim='-')
- constructor

register(views, model=None, base_url=None, prefix=None)
- method to add your views for model

urls
- property, returns URLs sequence for all registered views that can be included in urlpatterns

autodiscover
- method which goes over settings.INSTALLED_APPS and looks for apps with smarter_views modules, which it imports, so they can register their views.

Site

Constructor gets two keyword arguments:

  1. prefix=None, for prefixing URL names for views registered with site object, like '%(prefix)s-%(model)s-%(action)s'. If prefix if empty, URLs are named without prefix, like '%(model)s-%(action)s'.
  2. delim='-', delimiter for URL names, can be '-', '_' or empty string. URL names are composed with specified delimiter and with uderscore it would be like '%(prefix)s_%(model)s_%(action)s'.

Site.register

This method gets 1 required argument for views class and optional keyword arguments:

  1. model=None, model class for views. This argument is required if views class doesn't have 'model' property.
  2. base_url=None, base URL for views. If empty, then lower-case model name is used, so base URL becomes '%(model)s/'.
  3. prefix=None, prefix for URL names. If empty, then lower-case model name is used.

smarter.GenericViews

model
- class property, model class for views

defaults
- class property, dict with default options applied to all actions until being overriden by options

options
- class property, dict for views configration, each key corresponds to single action like 'add', 'edit', 'remove' etc.

deny(request, message=None)
- method, is called when action is not permitted for user, raises PermissionDenied exception or can return HttpResponse object for redirecting or rendering some page

get_url(action, *args, **kwargs)
- method, returns url for given action name

get_form(request, **kwargs)
- method, returns form for request

get_object(request, **kwargs)
- method, returns single object for request

get_objects_list(request, **kwargs)
- method, returns objects for request

get_template(request_or_action)
- method, returns template name or sequence of template names by action name or per-request

get_param(self, request_or_action, name, default=None)
- method, returns option parameter by name for action or per-request

get_initial(self, request)
- method, returns form initial data per-request

<action>(request, **kwargs)
- method, 1st (starting) handler in default pipeline

<action>__perm(request, **kwargs)
- method, 2nd handler in default pipeline, checks extended permissions, e.g. per-object permissions (basic checks are handler separatelly)

<action>__form(request, **kwargs)
- method, 3rd handler in default pipeline, manages form processing

<action>__save(request, form, **kwargs)
- method, called from <action>__form when form is ready to save, saves the form and returns saved instance

<action>__post(request, **kwargs)
- method, 4th handler in default pipeline for post-processing: save messages, extend render context, etc.

<action>__done(request, **kwargs)
- method, 5th (last) view handler in default pipeline, performs render or redirect

Pipeline

Each action like 'add', 'edit' or 'remove' is a pipeline: a sequence (list) of methods called one after another. A result of each method is passed to the next one.

The result is either None or dict or HttpResponse object:

  1. None - result from previous pipeline method is used for next one,
  2. dict - result is passed to next pipeline method,
  3. HttpResponse - returned immidiately as view response.

For example, 'edit' action pipeline is: 'edit' -> 'edit__perm' -> 'edit__form' -> 'edit__post' -> 'edit__done'.

Note about __perm step. Basic permissions are checked before pipeline start view (e.g 'edit'), as if view were decorated with permission_required decorator. Actualy we're not using decorator, because we need to call our custom deny() method if permissions are not sufficient, but it's not the key. The key is you don't need to check basic permissions in custom __perm method, it's necessary for per-object permissions checks.

Method Parameters Result
edit request, **kwargs 'pk' {'obj': obj, 'form': {'instance': obj}}
edit__perm request, **kwargs 'obj', 'form' pass (None) or PermissionDenied exception
edit__form request, **kwargs 'obj', 'form'
{'form': form, 'obj': obj, 'form_saved': True}
- form successfully saved
{'form': form, 'obj': obj}
- first open or form contains errors
edit__post request, **kwargs 'obj', 'form', 'form_saved' pass (None) by default
edit__done request, **kwargs 'obj', 'form', 'form_saved' render template or redirect to obj.get_absolute_url()

Note, that in general you won't need to redefine pipeline methods, as in many cases custom behavior can be reached with declarative style using options. If you're going too far with overriding views, that may mean you'd better write some views from scratch separate from "smarter".

Reversing URLs

Every action mapped to named URL. Names are composed as:

[site prefix][delimiter][views prefix][delimiter][action]

Where:

So, in Getting started example named URLs are 'page-add', 'page-edit', 'page-remove', etc., as we don't provide any custom prefixes and delimiter is '-' by default.

Pipeline example

For deeper understanding here's an example of custom pipeline for 'edit' action. It's not actually a recommended way, as we can reach the same effect without overriding edit method by defining options['edit']['initial'], but it illustrates the principle of pipeline.

import smarter

class PageViews(smarter.GenericViews):
    model = Page

    def edit(request, pk=None):
        # Custom initial title
        initial = {'title': request.GET.get('title': '')}
        return {
            'obj': self.get_object(request, pk=pk),
            'form' {'initial': initial, 'instance': obj}
        }

    def edit__perm(request, **kwargs):
        # Custom permission check
        if kwargs['obj'].owner != request.user:
            return self.deny(request)

    def edit__form(request, **kwargs):
        # Actually, nothing custom here, it's totally generic:
        # we should validate & save form and then return dict
        # with 'form_saved' set to True if it's ok.
        kwargs['form'] = self.get_form(request, **kwargs)
        if kwargs['form'].is_valid():
            kwargs['obj'] = self.edit__save(request, **kwargs)
            kwargs['form_saved'] = True
        return kwargs

    def edit__done(request, obj=None, form=None, form_saved=None):
        # Custom redirect to pages index on success
        if form_saved:
            # Success, redirecting!
            return redirect(self.get_url('index'))
        else:
            # Start edit or form has errors
            return render(request, self.get_template(request),
                          {'obj': obj, 'form': form})

Complete example

You may look at complete example source here:

License

Copyright (c) 2013, Alexey Kinyov <rudy@05bit.com> Licensed under BSD, see LICENSE for more details.

 
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