Marketplace - Comments - Milestone 3

In this assignment, you will expand your classified ads web site to add functionality equivalent to:

https://market.dj4e.com/m3

The primary additions from the previous milestone are to add comments for each ad. You must keep all the features from previous assignments working. You can log into this site using an account: facebook and a password of Marketnn! where "nn" is the two-digit number of Dr. Chuck's race car or the numeric value for asterisk in the ASCII character set.

You will build this application by borrowing parts and pieces from the code that runs

https://samples.dj4e.com/

and blending them into a your application.

Note About using AI with this Assignment

By this point in the course, you should already have the earlier assignments working correctly. While it’s fine to use AI to help diagnose specific errors, one of the worst approaches is to take a file you’ve been developing for weeks, hand it to an AI, and paste back a completely rewritten version without reviewing it carefully.

AI-generated solutions often “work” in the sense that they run without crashing, but they may remove or alter details the autograder expects. This can cause confusing autograder failures that are very hard to untangle.

There are many ways to solve these assignments that are roughly equivalent, but the autograder is not checking for just any equivalent solution. It's verifying that you’ve adapted the provided sample code in the expected ways.

If AI produces a solution that is only “approximately” like the samples, it probably won’t pass. And if AI overwrites working code you already built and have working perfectly, you may find yourself needing to start over from the beginning.

Before you Start: Taking a Snapshot of Your Previous Assignment

We want to take a snapshot of your previous assignment code using the git version management tool before we start making schanges to your code. Only do this once and only once after you have fully completed the previous assignment before you start editing your files for this assignment.

You should already have your github identity set up. The following should print your name

git config --global user.name

If you do not see your name, following the instructions to configure git at dj4e-samples/README.md

Once your git account is configured, run these commands:

cd ~/django_projects/market
git tag             # Make sure you don't already have a mkt2 tag (only do this once!)

git add .
git commit -a -m mkt2
git tag -a mkt2 -m mkt2
git tag             # Make sure you do have a mkt2 tag

The whole ~/django_projects/market folder is a git repository so you can use git for many cool things. But for now we are just making sure you have a "re-spawn" point if AI breaks your code badly.

The instructions to "revert" to the saved tag are at the bottom of this document. Hopefully you won't need to use them.

Adding Comments to the Ads Application

Important Note: If you find you have a problem saving files in the PythonAnywhere system using their browser-based editor, you might need to turn off your ad blocker for this site - weird but true.

In this section, you will pull bits and pieces of the forum sample application into your ads application to add support for comments for each ad.

(1) Update your models.py adding the comment feature from the forums/models.py

class Ad(models.Model) :

    ...
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    comments = models.ManyToManyField(settings.AUTH_USER_MODEL,
        through='Comment', related_name='comments_owned')
    ...

class Comment(models.Model) :
    text = models.TextField(
        validators=[MinLengthValidator(3, "Comment must be greater than 3 characters")]
    )

    ad = models.ForeignKey(Ad, on_delete=models.CASCADE)
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)

    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    # Shows up in the admin list
    def __str__(self):
        if len(self.text) < 15 : return self.text
        return self.text[:11] + ' ...'

Do not add the Forum model - simply connect the Comment model to the Ad model. Of course do the migrations once you have modified the model successfully.

(2) Pull the CommentForm class from forums/forms.py into your forms.py.

(3) Adapt the get() method from ForumDetailView to your AdDetailView to retrieve the list of comments and create the CommentForm and pass them into your mkt/templates/mkt/ad_detail.html template through the context.

(4) Adapt the mkt/templates/mkt/ad_detail.html template to show comments and show a delete icon when a comment belongs to the current logged in user.

(5) Also add the ability to add a comment to an ad in ad_detail.html when the user is logged in by looking at the techniques in forums/templates/forums/detail.html.

(6) Add a route in urls.py for the ad_comment_create and ad_comment_delete routes from forums/urls.py. Make sure to use the same URL patterns as shown here:

urlpatterns = [
    ...
    path('ad/<int:pk>/comment',
        views.CommentCreateView.as_view(), name='ad_comment_create'),
    path('comment/<int:pk>/delete',
        views.CommentDeleteView.as_view(success_url=reverse_lazy('mkt:all')), name='ad_comment_delete'),
]

(7) Adapt the comment related views from forums/views.py and put them into your views.py.

(8) You will have to adapt the forums/templates/forums/comment_delete.html template to work in your ads application.

Manual Testing

It is always a good idea to manually test your application before submitting it for grading. Here are a set of manual test steps:

Do Some or All of the Challenges

You will have to finish these by the next assignment - so you might as well work on them now. And they are fun.

(1) Make yourself a gravatar at https://en.gravatar.com/ - it is super easy and you will see your avatar when you log in to your application and elsewhere with gravatar enabled apps. The gravatar can be anything you like - it does not have to be a picture of you. The gravatar is associated with an email address so make sure to give an email address to the user you create with createsuperuser.

(2) Change your home/static/favicon.ico to a favicon of your own making. I made my favicon at https://favicon.io/favicon-generator/ - it might not change instantly after you update the favicon because they are cached extensively. Probably the best way to test is to go right to the favicon url after you update the file and press 'Refresh' and/or switch browsers. Sometimes the browser caching is "too effective" on a favicon so to force a real reload to check if the new favicon is really being served you can add a GET parameter to the URL to force it to be re-retrieved:

https://market.dj4e.com/favicon.ico?x=42

Change the x value to something else if you want to test over and over.

(3) Make social login work. Take a look at github_settings-dist.py, copy it into market/config/github_settings.py and go through the process on github to get your client ID and secret. The documentation is in comments of the file. Also take a look at dj4e-samples/urls.py and make sure that the "Switch to social login" code is correct and at the end of your market/config/github_settings.py.

You can register two applications with github - one on localhost and one on PythonAnywhere. If you are using github login on localhost - make sure that you register http://127.0.0.1:8000/ instead of http://localhost:8000/ and use that in your browser to test your site. If you use localhost, you probably will get the The redirect_uri MUST match the registered callback URL for this application. error message when you use social login.

Resetting Your Database

If python manage.py check is working and python manage.py makemigrations is working, you may have made a series of changes to models.py and ended up with a mis-match between your migration files and database have become confused causing makemigrations to fail.

We have provided a Python script that completely resets your Django project's database and removes all migration files, allowing you to start fresh with a clean database schema. This is particularly useful when migration files have become corrupted or when you need to restructure your models significantly.

First we update the samples code so you have the latest helper scripts.

cd ~/dj4e-samples/
git checkout django52
git pull origin django52

Then follow the instructions at dj4e-samples/tools/README_DB.md

The reset script will:

Discarding Code Changes and Going back to an earlier tag

If you make a mistake (or if AI makes a mistake) and you paste it into your code and break everything (i.e. not migrations and models.py) you can decide to reset your code base to the tag your created above (if you created a tag). Follow these instructions - move slowly and if things blow up - get help.

If python manage.py check is working and python manage.py makemigrations is not working, you may not need to throw your code away and might want to try a database reset first.

First we update the samples code so you have the latest helper scripts.

cd ~/dj4e-samples/
git checkout django52
git pull origin django52

Then follow the instructions at dj4e-samples/tools/README_GIT.md

If you go back, and have discarded your code changes - you probably need to reset your database as well as shown in the previous section.