dj4e_autos.md

Login / Autos CRUD

This assignment is to build a fully working CRUD (Create, Read, Update, and Delete) application to manage automobiles and their makes (i.e. Ford, Hyundai, Toyota, Tata, Audi, etc.).

This application will be based on this folder in the samples repo:

https://github.com/csev/dj4e-samples/tree/main/autos

Do not clone this repository for this assignment. You will make a new project and application in your django_projects folder and use this application as sample code.

This application will be similar to:

https://crud.dj4e.com

The login information is as follows:

Account: dj4e-crud
Password: dj4e_nn_!

The 'nn' is a 2-digit number that by now, you should be able to easily guess.

Making a New Application

Activate any virtual environment you need (if any) and go into your django_projects folder and start a new application in your mysite project (this project already should have the 'hello' application from a previous assignment).

workon django42      # or django4 as needed
cd ~/django_projects/mysite
python manage.py startapp autos

Extending the home (i.e. main) page

Since we will build a number of applications in this project, we will use the home application to provide convienent urls to switch between applications.

And you should have a file mysite/home/templates/home/main.html that has the text for the top-level page. You can keep the "Hello World" text in the page somewhere.

Add a link to the "/autos" url in mysite/home/templates/home/main.html and anything else the autograder needs:

<li><a href="/autos">Autos CRUD</a></li>

It is a list because we will be adding more applications in future assignments. :)

Building the Autos Application

The essense of this task is to adapt the code from:

https://github.com/csev/dj4e-samples/tree/main/autos

and make it work in your autos project. As always there is a lot of code in dj4e-samples - be careful copying - and only copy code when you know why you are copying it. Go slowly.

Here are some tasks:

• Go into your dj4e-samples folder and do a git pull to get the latest version of the samples code.

• Create mysite/home/templates/registration folders and copy the (login.html) template from dj4e-samples into mysite/home/templates/registration/login.html.

• Copy the file from dj4e-samples/home/templates/base_bootstrap.html into your mysite/home/templates/base_bootstrap.html - this will be used in your autos/templates and make our HTML look better by applying the Bootstrap and other styling libraries.

• Edit mysite/mysite/settings.py add the autos application to the list of INSTALLED_APPS. You can follow the pattern of the HomeConfig line in that file.

• Edit mysite/mysite/urls.py and add the accounts/ path so you can use the Django built in login features. (Authentication Views). Also edit mysite/mysite/urls.py to route autos/ urls to autos/urls.py file.

    path('accounts/', include('django.contrib.auth.urls')),  # Add
    path('autos/', include('autos.urls')),                   # Add
  

• Edit the autos/views.py file to add views for the list, create, update, and delete views for both autos and makes based on the sample code.

• Create/Edit the autos/urls.py file to add routes for views for both autos and makes

• Create/Edit the autos/forms.py file to add the form for MakeForm

• In your views.py file, you can start out using the Make views from the sample code, but once you have the application working, you should come back and rewrite the Make views using the same patterns as the Auto views. If you switch to the pattern in the Autos views and use the generic edit views on your Make views you no longer need to have a MakeForm or forms.py. You can either write the long version of the views or the short version of the views - the short version is easier to code but more challenging to understand because it relies so heavily on a complex parent object and inheritance.

• Edit the autos/models.py file to add Auto and Makes models with a foreign key from Autos to Makes.

• Run the python manage.py check until you see no errors

• Run the python manage.py makemigrations until it has no errors. Sometimes when you make changes to models.py, the makemigrations will pick up on the changes and ask you for example if you want to rename a field. Sometimes you make a change to your models.py and makemigrations gets stuck or lost. If migrations gets stuck, you might need to start with a fresh database.

• Run the python manage.py migrate to create the database.

• Edit autos/admin.py to add the Auto and Make models to the Django administration interface.

• Run the python manage.py check until you see no errors

• Create a superuser so you can test the admin interface and log in to the application.

• Create the necessary template files in autos/templates/autos to support your views. Note that the the second sub folder under templates is there to make sure that templates are not inadvertently shared across multiple applications within a Django project.

• Find the line in your base_bootstrap.html that looks like this:

    <meta name="dj4e-code" content="99999999">
  

  and change the 9999999 to be "missing"

Make sure to check the autograder for additional markup requirements.

Things that can go wrong

If you ever get a 405 error on a Django page it probably means that you have defined a view class that does not have a get() method. For example if you meant to say this:

class AutoUpdate(LoginRequiredMixin, UpdateView):
    model = Auto
    fields = '__all__'
    success_url = reverse_lazy('autos:all')

But instead you did:

class AutoUpdate(LoginRequiredMixin, View):
    model = Auto
    fields = '__all__'
    success_url = reverse_lazy('autos:all')

(i.e. you extended View instead of UpdateView) - the result is that there is no def get(self, request): in your view. So you get the 405 HTTP status code (invalid method) when you navigate to the URL that forwards to the view.

Manual Testing

It is always a good idea to manually test your application before submitting it for grading. Here is a rough outline of the steps that the autograder will take to grade your application. You should run them by hand before running the autograder and make sure they work without error.

• Log in
• Add a make
• Add an auto selecting the make
• View the makes
• Update the make and press 'Cancel' - Should go to the auto list list
• Update the make, make a change and save it - Should go to the auto list
• The make for the auto in the list should be automatically updated
• Update the auto, change its nickname and save it - it should be updated in the auto list
• Add a second make
• Add a second auto using the second make
• View the autos - make sure the second car and make are present
• Delete the second make - the auto corresponding to the make should go away automaticallr (Cascade in action)
• Delete the first auto

References

• Autos CRUD Sample Code

• Installing Django Locally

• Embedding SVG in Markdown

<script> var d= new Date(); var code = "42"+((Math.floor(d.getTime()/1234567)*123456)+42) document.getElementById("dj4e-code").innerHTML = code; </script>