DIY: Hello World / Sessions

In this assignment, you will make two new applications in your django_projects to make it so that the / path actually returns a page and add a bit of code to make use of sessions.

A key element of this assignment is that we will tell you "what to do" and less exact steps to cut and paste. It is time for you to understand how to "Do It Yourself" (DIY).

This assignment will not have any models - just views. In this assignment you will be looking at the dj4e-samples code and figuring out how to read and adapt sample code. You should make sure to get the latest updates by doing the following:

cd ~/dj4e-samples
git pull

In general, be careful copying code from dj4e-samples - it often has much more code than your program needs - so know what you are looking at before you copy code into your application.

Building a Main Page

It is time for the "/" in your application URL to actually refer to a real page instead of throwing a "404 Not Found" error. We will store this page (and other project-wide bits) in an application named "home". To get started:

cd ~/django_projects/mysite
python manage.py startapp home

Create an HTML file in ~/django_projects/mysite/home/templates/home/main.html with the following HTML:

<ul>
<li><p><a href="/polls">A Polls Application</a></p></li>
</ul>

You can add more HTML - but this list and links should be somewhere in the template.

Edit the file ~/django_projects/mysite/mysite/urls.py and add following path route:

path('', TemplateView.as_view(template_name='home/main.html')),

You will need to make sure to add the proper python imports at the top of the file to make this work. There are lots of examples of the use of TemplateView in the urls.py files in dj4e-samples and in the lecture materials. Figuring out exactly how to change your urls.py is one of the DIY aspects of this assignment.

Then edit the file ~/django_projects/mysite/mysite/settings.py and add a line to load the home application. Simply duplicate the line in INSTALLED_APPS for the polls application and edit it to reference home and follow the pattern of case from the polls line.

Make sure to run:

python manage.py check

To see if your changes have syntax errors, then Reload your web application and navigate to the top level path (i.e. no path). You should no longer get a "404" and instead be able to navigate to the polls application by clicking on the link. Congratulations! You now have a web site that is not broken.

Note that this page is not present on the https://djtutorial.dj4e.com/ server. It still shows "404" when you navigate to the top URL.

Playing With Sessions (DIY)

Your next goal is to make a new application named hello. It will work like: https://djtutorial.dj4e.com/hello. This uses the Django session to start a variable at 1 and for each refresh increment the value in the session, and when the number n the session is > four reset the session variable to one,

Your views.py will be adapted from

https://github.com/csev/dj4e-samples/blob/main/session/views.py

We walk through this code in the lectures and you can experiment with this sample code at https://samples.dj4e.com/session/sessfun.

You will need to:

  1. Use startapp to create a folder for the application and have Django create empty files like views.py and models.py in the hello folder.

    cd ~/django_projects/mysite python manage.py startapp hello

  2. Create a hello/urls.py to route all requests to the hello application to a view function that you will write in views.py - You can look at your polls/urls.py to see how the file is constructed in general and adapt it to create hello/urls.py. You will only need one urlpattern in the hello application. You will only write a single view function that will both set a cookie and implement the session. If your view function was named myview, the path will look as follows:

    path('', views.myview),

  3. Change the project-wide ~/django_projects/mysite/mysite/urls.py to set up the path to the new application's urls at /hello. Look at the line in that file that routes paths to the polls application and adapt it for your hello application.

  4. Edit the file ~/django_projects/mysite/mysite/settings.py and add the hello application following the pattern that you used to add the polls application to INSTALLED_APPS - again - the exact code is something you figure out from looking at dj4e-samples or from the lectures.

Add a link to ~/django_projects/mysite/home/templates/home/main.html with the following HTML:

<li><p><a href="/hello">Test the session</a></p></li>

These instructions are telling you what to do not how to do it. This is another DIY part of this assignment - look at sample code and understand it - no more cutting and pasting of chunks of code without knowing how the pieces fit together.

This assignment is not a lot of code. It is more about learning to read, reuse, and adapt code. There is lots of sample code in dj4e-samples - probably too much code. If you just copy and paste everything from dj4e-samples it will be difficult to make this work. When looking at code written by others, it is important to know what is going, what can be copied, and what not to copy.

Also make sure to check the auto grader for any additional requirements for this assignment.