django: routing users through a complex app with class-based views - django

I'm an advanced beginner at django and python. I'm writing an app to handle registration and abstract submission for a conference, and I'm trying to use class-based views. Users get an emailed link that includes their registration code in the url. Starting at this url, users move through a series of views that collect all the necessary info.
The complication comes from the fact that users often stop half way through, and then want to complete the process several days or weeks later. This means that they might continue from the current page, or they might just click that original link. In addition, after several weeks they might have missed certain deadlines, so, e.g., they can no longer submit an abstract (but they can still register). Along the way, they have checked or unchecked various options that also influence the path they should take through the app.
My question is: where is the best place to put the logic that determines if the user is currently allowed to view that page, and if not, the best url to redirect them too? I thought I would create a custom view class that, e.g., overrides the dispatch method to include global checks (e.g., is conference registration open?), and then subclasses could add additional checks (e.g., has the user entered all the necessary info for her abstract?). The problem I ran into was that the checks were run in the wrong order (I want base class checks run first). I then started investigating custom view decorators or custom middleware. At this point I realized I could use some expert advice about which approach to take. (If it matters, I am not using the django authentication system.) Thanks in advance.

Maybe the form wizard could help you managing the viewing sequence.
In general django greybeards advocate keeping row-wise logic in Models, and table-wise logic in Managers, so it seems appropriate to keep complex view logic in a master view class.
The wizard class can help maintain the order of the views, but to resume an out-dated session you may need to do some model saves (which could get too complex very quickly) or some cookie handling.
In the past, when presented with a similar situation, I took the simplest route and separated user registration and the task that the user wants to perform (event registration). The user registers once but if they fluff up the event registration, they just have to log back in at a later date and do it again (their hassle - not yours!).

Related

Multiple reset passwords in django

I have a project which have a personal app, where the login takes place, and a question app which also includes a profile page. I have managed to reset pasword from the login page, but when I try to do the same in the question app (using different templates, because I do not want the same on these pages), it just goes directly to the login reset template.
I thought it would be enough to just add a new registration folder in the questions app, but it still goes searching in the personal app I think.
Is it possible to just fix this using the django auth views or do I have to create my own views for the questions app?
You will need to create separate views, as well as separate templates.
First, make sure that you understand the User model, and how authentication works in Django. The core docs have plenty of information on that.
Second, look at what you are trying to do and create a view specifically for the template you are creating. Make sure that view processes the data the way that you want to, and that it redirects where you want the user to be redirected to after making the update.
One question to ask yourself though, before you go through this trouble is "Do I really need to have two places to do this?"
Having more than one location to handle password resets is not likely to end up being what you actually want in the long run. I would personally keep all of the account manipulation views in one place so that you don't mess something up if you decide to change something in one place and forget in another.
Two principles that are important when developing any kind of site are KISS and DRY. KISS is just the traditional keep it simple.
DRY means don't repeat yourself.
Unless there is a NEED to have the code be in two different places, it is a bad idea. ESPECIALLY with account related things.

Application logic in view code

Should I be writing application logic in my view code? For example, on submission of a form element, I need to create a user and send him an activation email. Is this something to do from a view function, or should I create a separate function to make it easier to test down the road? What does Django recommend here?
I found it very hard to figure out where everything goes when I started using django. It really depends on the type of logic you are writing.
First start with the models: model-methods and managers are a good place to perform row-level logic and table level logic i.e. a model manager would be a good place to write code to get a list of categories that are associated with all blogposts. A model method is a good place to count the characters in a particular blogpost.
View level logic should deal with bringing it all together - taking the request, performing the necessary steps to get to the result you need (maybe using the model managers) and then getting it ready for the template.
If there is code that doesn't fit in else where, but has a logical structure you can simply write a module to perform that. Similarly if there are scraps of code that you don't think belong, keep a utils.py to hold them.
You shouldn't perform any logic really in your templates - instead use template tags if you have to. These are good for using reusable pieces of code that you you neither want in every request cycle nor one single request cycle - you might want them in a subset (i.e. displaying a list of categories while in the blog section of your website)
If you do want some logic to be performed in every request cycle, use either context processors or middleware. If you want some logic to be performed only in one single request cycle, the view is probably the place.
TLDR: Writing logic in your view is fine, but there are plenty of places that might be more appropriate
Separating the registration code into it's own function to make testing easier is a good reason. If you allowed admins to register users in a separate, private view, then a registration function would be more DRY. Personally, I don't think a little application logic in the code will do to much harm.
You might find it instructive to have a look at the registration view in the django-registration app -- just to see how it's written, I'm not saying you should or have to use it. It has encapsulated the user registration into it's own function (there's a level of indirection as well, because the registration backends are pluggable).

Should I modify/extend the admin interface, or write my own CRUD views/templates?

I'm trying to write a simple CRM app in Django; partly as a learning exercise and partly for in-house use.
My schema is slightly complex, as rather that have a single Contact model (with a home phone, work phone, home email, etc.), I have stripped down Cntact model plus a Phone model, an Email model, etc., with a ForeignKey pointing back to a Contact. The point is to let Contacts have an arbitrary number of phone numbers, email addresses, etc. Simple, right?
I have some working views and templates for displaying the data - no issues there. And with only a very small amount of poking at admin.py I have a um...eight different TabularInlines set up, and the admin interface works to create and edit the data...but it's ugly and clunky to the point of unusability, and of course there's no conception of permissions or anything. I'm also not really a fan of having a completely different interface for displaying and searching through the data than for editing and adding contacts...I'd like as much as possible to be done inline, so that I can search for a name, look at the record, click "add note", have it popup a form, fill in the details, click submit, and be done, all with AJAXy goodness so there's no page reloads.
Question: Should I plug away at modifying the admin interface to try and make it usable for a user-facing app? And if so, can anyone point me to a good guide or example where someone has really changed the admin interface to make it work for user-facing CRUD operations?
Or should I just go ahead and write my own CRUD views? And if so, can anyone point me to a good guide or example where someone has written custom CRUD views that work with lots of ForeignKeys and inlines? Ideally I want a form that displays a single Contact, all his Email records, plus a blank form to add a new Email record, plus a button to add more blank forms, plus his Phone records, plus a blank form, and so on for all 8 of my associated models.
(Or am I thinking about this all wrong? Any advice appreciated.)
For our intranet, we use ModelAdmin subclasses (not mounted on the admin site via admin.site.register) for most of our C(R)UD views. By using custom templates for the views, it doesn't look like Django admin at all. What is very convenient though, is that it already handles all the validation/saving for us.
In general, I found admin-"hacking" quite useful to quickly write up C(R)UD views and usually with relatively small changes to your ModelAdmin subclass, you can make it work for your use case.
So I'd vote for use ModelAdmin, but not the one you use in admin, hook a different template and come up with some fancy CSS.
I successfully created a software on top of admin.
The admin hooks (these days) allow very fine-grained customizations, i.e. in general you only need to touch what you want to change.
The changes can go from a trivial cosmetic adjustment to a complete swap-out:
If you provide templates/admin/base.html your admin site can look any way you like. And of course, a navigation bar at the top could include links to some of your own views. Watch out not to hardcode URLs in your links, always reverse.
You can overload ModelAdmin's "change_view", "changelist_view" etc. and swap them for your own views. For example I replaced a default changelist and its simple filtering with a search interface that allows dynamic queries to be built, result columns to be customized by the user, and loading/saving of these searches. That didn't affect any of the other views of that ModelAdmin.
Overloading a ModelAdmin's "get_urls()" let's you rewrap existing admin urls to go to your own views. I did the latter for one model where I wanted the simple Add screen to be replaced by a totally customized Wizard (only leaning on ModelForm).
Don't forget the simplest approach, esp. regarding your "AJAXy goodness": Just define "css" and "js" in your ModelAdmin's Meta. Want to move an inline from the bottom to sit between third and fourth field, and that's not possible via parameters? A one-liner in jquery.
Check out "django-grappelli" for an example of how to improve admin look and feel.
What did you mean by "and of course there's no conception of permissions or anything"?

Avoiding circular dependencies in Django applications

While working on my Django-based projects I'm always trying to follow Django's approach to reusable apps - I'm trying to decouple my applications from each other and especially trying to avoid cross references but sometimes it does not seem to be possible.
Let's consider a simple example with 2 applications: articles and users. Articles application defines article model, articles list view and single article view, users application defines user model and user profile view. Article is referencing user from the author field, so articles application is obviously dependent on users application which is fine.
But when it comes to user profile, I want to display latest articles authored by the user (and may be latest articles viewed by the user) on that page but that makes users application aware of articles application which is what I'm trying to avoid.
I can obviously try to push all such references to the template level but it still does not solve the issue completely and at the same time may be very inefficient in terms of database queries sometimes.
What do you guys do in such cases?
If you are really set on not having any conversation between the 'user' app and the 'article' app, then you need a third app to act as interface. That would know about users and articles and define all the coupling between them. Your article view would be in there, since it has to get the user data, and your user profile view would be in there, because it needs to say "Fred wrote 5 articles".
Whether this level of decoupling is worth it, I don't know. Sometimes programming for re-usability gets in the way of making the thing usable in the first place.
The standard (or preferred) way of keeping coupled apps decoupled is to add a conditional coupling - like in some apps that try to import django-notification and only if they find it, they report events to it.
Still, if you have two apps that talks to each other by design, then I don't see any point in decoupling them - there are plenty of examples in Django world of apps that just require other apps. Note that I'm talking here about writing real-world software, not about some academic delibrations :-)
It seems that in this case, the dependency of users on articles is in a method, not a field. (Whether it's a model method, a model class method, or a manager method is immaterial). If that's so, you can do a lazy import of articles inside the method. By the time this import is performed, users.models will be fully loaded, so even if this is a circular import, it will not cause problems. The "import users" statement in articles will not have to re-load users and will have the full users namespace available.

Django app that can provide user friendly, multiple / mass file upload functionality to other apps

I'm going to be honest: this is a question I asked on the Django-Users mailinglist last week. Since I didn't get any replies there yet, I'm reposting it on Stack Overflow in the hope that it gets more attention here.
I want to create an app that makes it easy to do user friendly,
multiple / mass file upload in your own apps. With user friendly I
mean upload like Gmail, Flickr, ... where the user can select multiple
files at once in the browse file dialog. The files are then uploaded
sequentially or in parallel and a nice overview of the selected files
is shown on the page with a progress bar next to them. A 'Cancel'
upload button is also a possible option.
All that niceness is usually solved by using a Flash object. Complete
solutions are out there for the client side, like: SWFUpload
http://swfupload.org/ , FancyUpload http://digitarald.de/project/fancyupload/
, YUI 2 Uploader http://developer.yahoo.com/yui/uploader/ and probably
many more.
Ofcourse the trick is getting those solutions integrated in your
project. Especially in a framework like Django, double so if you want
it to be reusable.
So, I have a few ideas, but I'm neither an expert on Django nor on
Flash based upload solutions. I'll share my ideas here in the hope of
getting some feedback from more knowledgeable and experienced people.
(Or even just some 'I want this too!' replies :) )
You will notice that I make a few assumptions: this is to keep the
(initial) scope of the application under control. These assumptions
are of course debatable:
All right, my idea's so far:
If you want to mass upload multiple files, you are going to have a
model to contain each file in. I.e. the model will contain one
FileField or one ImageField.
Models with multiple (but ofcourse finite) amount of FileFields/
ImageFields are not in need of easy mass uploading imho: if you have a
model with 100 FileFields you are doing something wrong :)
Examples where you would want my envisioned kind of mass upload:
An app that has just one model 'Brochure' with a file field, a
title field (dynamically created from the filename) and a date_added
field.
A photo gallery app with models 'Gallery' and 'Photo'. You pick a
Gallery to add pictures to, upload the pictures and new Photo objects
are created and foreign keys set to the chosen Gallery.
It would be nice to be able to configure or extend the app for your
favorite Flash upload solution. We can pick one of the three above as
a default, but implement the app so that people can easily add
additional implementations (kinda like Django can use multiple
databases). Let it be agnostic to any particular client side solution.
If we need to pick one to start with, maybe pick the one with the
smallest footprint? (smallest download of client side stuff)
The Flash based solutions asynchronously (and either sequentially or
in parallel) POST the files to a url. I suggest that url to be local
to our generic app (so it's the same for every app where you use our
app in). That url will go to a view provided by our generic app.
The view will do the following: create a new model instance, add the
file, OPTIONALLY DO EXTRA STUFF and save the instance.
DO EXTRA STUFF is code that the app that uses our app wants to run.
It doesn't have to provide any extra code, if the model has just a
FileField/ImageField the standard view code will do the job.
But most app will want to do extra stuff I think, like filling in
the other fields: title, date_added, foreignkeys, manytomany, ...
I have not yet thought about a mechanism for DO EXTRA STUFF. Just
wrapping the generic app view came to mind, but that is not developer
friendly, since you would have to write your own url pattern and your
own view. Then you have to tell the Flash solutions to use a new url
etc...
I think something like signals could be used here?
Forms/Admin: I'm still very sketchy on how all this could best be
integrated in the Admin or generic Django forms/widgets/...
(and this is were my lack of Django experience shows):
In the case of the Gallery/Photo app:
You could provide a mass Photo upload widget on the Gallery detail
form. But what if the Gallery instance is not saved yet? The file
upload view won't be able to set the foreignkeys on the Photo
instances. I see that the auth app, when you create a user, first asks
for username and password and only then provides you with a bigger
form to fill in emailadres, pick roles etc. We could do something like
that.
In the case of an app with just one model:
How do you provide a form in the Django admin to do your mass
upload? You can't do it with the detail form of your model, that's
just for one model instance.
There's probably dozens more questions that need to be answered before
I can even start on this app. So please tell me what you think! Give
me input! What do you like? What not? What would you do different? Is
this idea solid? Where is it not?
Thank you!
I just released a simple app for this about a month ago: django-uploadify.
It's basically a Django template tag that acts as a wrapper for the very nifty Uploadify (requires jQuery). Using it is as simple as adding this to your template...
{% load uploadify_tags }{% multi_file_upload ‘/upload/complete/url/’ %}
The tag will fire events (1 per file) on both the client-side and server-side (Django signal) to indicate when an incoming file has been received.
For example, assuming you have a model 'Media' that handles all user-uploaded files...
def upload_received_handler(sender, data, **kwargs):
if file:
new_media = Media.objects.create(
file = data,
new_upload = True,
)
new_media.save()
upload_recieved.connect(upload_received_handler, dispatch_uid=‘whatever.upload_received’)
Check out the wiki for info on how to set it up and create the signal handlers (client/server).
About your conceptual implementation from above, here's a few points of consideration:
Having the app automatically create the "File Model" instance probably isn't as robust as people may already have their own models they're working with
If you want to implement any type of security or authentication, you need an open system and less of an 'auto-create' type
I really think signals/events are the way to handle this, and also handle the 'DO OTHER STUFF' part of what you mentioned.
My conclusion was that multi-upload can never really be a form widget in the sense that Django implements form widgets. 1 file will most likely be represented by 1 model instance (with some exceptions), which means that we end up with a situation where 1 widget can represent N model instances. However Django is setup so that a widget represents 1 value for 1 field in 1 instance. It just doesn't fit for the majority of use-cases to have it as a widget (hence why I went the template tag route).