This week, we’ll be focusing on going further with Django before we dive into REST APIs.

Today, we’ll be talking about deploying our Django apps to Heroku and using PostgreSQL.

Assignments

We will continue to improve and finish Habit Tracker this week. Today, you’ll start by deploying it to Heroku.

Resources

• Checklist for deploying to Heroku
• Django Recipes example app

Today we talked about creating models and building views. We specifically went over the 5 big views used everywhere in Django.

The Five Views

# - list many models
def cohort_list(request):
    cohorts = Cohort.objects.all()
    return render(request, "core/cohort_list.html", {"cohorts": cohorts})


# - show one model
def cohort_detail(request, pk):
    cohort = get_object_or_404(Cohort, pk=pk)
    return render(request, "core/cohort_detail.html", {"cohort": cohort})


# - create a model
def cohort_create(request):
    if request.method == "GET":
        form = CohortForm()
    else:
        form = CohortForm(data=request.POST)
        if form.is_valid():
            cohort = form.save()
            return redirect("cohort-detail", pk=cohort.pk)

    return render(request, "core/cohort_create.html", {"form": form})


# - update a model
def cohort_update(request, pk):
    cohort = get_object_or_404(Cohort, pk=pk)

    if request.method == "GET":
        form = CohortForm(instance=cohort)
    else:
        form = CohortForm(instance=cohort, data=request.POST)
        if form.is_valid():
            cohort = form.save()
            return redirect("cohort-detail", pk=cohort.pk)

    return render(request, "core/cohort_update.html", {"cohort": cohort, "form": form})


# - delete a model
def cohort_delete(request, pk):
    cohort = get_object_or_404(Cohort, pk=pk)

    if request.method == "POST":
        cohort.delete()
        return redirect("cohort-list")

    return render(request, "core/cohort_delete.html", {"cohort": cohort})

Other Resources

• The sample app from class
• URLs Lead the Way and Views on Views from Understand Django

Today, we will focus on understanding the database, how Django models interact with it, and how to model data for specific problems.

Assignment

This week, you will work on Habit Tracker. For Wednesday, you will want to have all your models created.

Data modeling problems for small groups

Small groups (use Google Meet or Zoom):

• Charlette, Nathan, Jon, Phil
• Kim, Derek, Babacar, Tom

Problem 1: You want to make an application for yourself to hold your favorite recipes. This application does not have users; since it’s just for you, there is no log in or registration. Recipes have ingredients and recipe steps. They also have “tags,” which allow you to put arbitrary categories on them like “breakfast”, “kid-friendly”, or “vegetarian.” Each recipe can have multiple tags; each tag can have multiple recipes. What’s the data model?

Problem 2: Take the above problem. You now want to make it so other people can use your application. Each person has their own recipes they own. Recipes can be public or private; private ones are only visible to the user who made it. What’s the new data model?

Problem 3: Take a simple version of Twitter. Users can make posts. Each post can have many images. Users can follow other users in order to see a list of posts from everyone they follow. Users can “like” posts to designate that they think it’s a great post. What’s the data model?

Problem 4: Take the above problem. You want to make it more like Facebook. Users don’t have a one-way follow; instead, they have “friends,” which is a two-way relationship. In addition, users can comment on their friends’ posts. What’s the data model?

Problem 5: Imagine a system for a library. The library has one or more copies of each book it owns. Users can check out individual copies of a book and the library needs to know who currently has the book. Books are due two weeks after check out. First, what questions do you need to ask to complete this data model? For these questions, decide on an answer. Then, what’s the data model?

Resources

• Momentum Django project template
• Data modeling explained in 10 minutes
• Logical database design using entity-relationship modeling - This looks intimidating and is part of a manual for a database we won’t use, but is really good material.
• Django model relationships
• Django model queries
• Video: Building effective Django queries with expressions - DjangoCon 2019 video on queries
• Momentum Codex - Django Intro

Welcome, all, to Phase 3! We are about to have a very exciting five weeks together.

We’re going to take the first week to strengthen our knowledge of Django with a set of lessons I call “Django from the Ground Up.” Now that you’ve gotten familiar enough with it to see it work together, we’ll break down how to use each piece effectively.

After that, you’ll move into your front-end and back-end classes.

Schedule

Week 1 (Nov 2-6)

• Lecture M, W, Th from 9:30-11:30 AM
• Small groups M, W, Th from 1-3 PM
• Check-in with Clinton, M, W, Th from 3:30-4 PM
• Tuesday: go vote, study hard

Weeks 2-5

In Phase 3 proper, we meet three days a week (M, Tu, Th). Front-end meets from 9:30-11:30 AM and back-end meets 2-4 PM. You will schedule two one-on-ones with me as well: Wednesday is reserved for those.

Your Zoom link: Clinton’s Classroom

Post-video note

By the end of class we had gotten as far as getting a 403 request from our Django application. The solution is to add the following to our AJAX request:

headers: { "x-csrftoken": form.elements["csrfmiddlewaretoken"].value },

This ensures that the token generated by csrf_token is included in the request (when you submit a form normally django knows how to handle it, but when you send an AJAX request this needs to be specified).

Video Links

• Morning Video
• Password: 0*nMSN^.
• Afternoon Video
• Password: 4jV8+!9k