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Build Views

Getting Started With Django: Building a Portfolio App Martin Breuss 06:19

In this lesson, you’re going to create your views and have a visit with your good friend, the AttributeError! According to this error message, the module project.views has no attribute called all_projects, so head over to views.py to create this view:

# Create your views here.
def all_projects(request):
    return render(request, 'all_projects.html')

Now, you’re getting a new error message, TemplateDoesNotExist, because you haven’t yet created this template, so Django doesn’t know what to render.

00:00 Let’s go ahead and create our views. As you already know from the last video, we’re going to start this one off with a good old friend, the AttributeError.

00:10 'project.views' has no attribute 'all_projects'. Great! So, let’s head over there

00:16 inside of views.py and create this view. We’re looking for one called all_projects, that’s the one we want to create. If I say def all_projects(), taking the request, as always, as input, and we want to return render().

00:39 We want to return the request and template_name, and that’s all we have to worry about for now. So, I’m returning the request, and as the template_name, I’m going to put 'all_projects.html'.

00:55 So, what’s going to happen over here?

00:59 It changed. It seems to be running fine. Let’s head over—

01:06 this slide is already telling us what to expect. If I reload this here, I’m going to get the TemplateDoesNotExist error. Again, just simply because I have not created this template yet, and that’s why it’s telling me it cannot find this template and doesn’t know what to render. Great!

01:26 So, back to here. We know already how to fix this TemplateDoesNotExist, right? We’re going to have to go in here, templates/projects/, and create the template in here with the same name. We’re going to do that in just a moment. For now, let’s focus on the view. In this case, we went to make a query to the database.

01:43 We want to return all the projects, and the views is where the logic of the code happens. So, what we want to do in here is query the database to return all Project objects that we have in there. So, you might be wondering how to do that, and it’s actually exactly the same code that we used when we were inside of the Django shell.

02:10 So, if you remember what I ran in there to retrieve all the objects from the database, it was something that went like Project.objects.all(), right? And we want to save this to a variable, so I’m going to say projects = this.

02:30 Now, this is not working yet. It’s telling me, also—it’s red underlined, and the reason is simply that I didn’t import the Project model. Go ahead and do that. from…

02:50 Here it is. So, from our projects app in the models file, I’m going to import the Project class, and now I’m able to call Project.objects.all(). This is actually working.

03:02 So, usually, the suggestions are very helpful. Sometimes they’re a bit off, so don’t worry about it here. Okay, so I’m returning this projects.

03:10 What can I do with this? One thing I can do, just for us to take a look, I can print them out. I’ll do that.

03:23 So, one interesting thing for me when I was learning Django is to understand when is this code going to get called? I think that’s very important, and that’s why we’re putting this print() statement in here. My server is running, you see that? It’s all fine, but nothing is printed.

03:37 And that’s because this function has not run. Now, the question is, when does it run it? The answer to this question is simply when we go to the URL and make a request!

03:48 In this case, our template still does not exist. But I made a request, which, if we go here,

04:00 printed out, before giving us the error—because the template doesn’t exist—but before that, this print() statement ran, so we get this QuerySet Project with one Project object in there.

04:11 It’s the same thing that we got in the Django shell with the exact same code, right? So, all that’s happening is Django is routing through our setup, it’s routing the request to this view, and then executes the code—whatever code is sitting in here. In this case, we’re making a call to the database and retrieving all objects, printing out those objects to the console—that’s happening down here—and then we’re trying to render a template that currently doesn’t exist yet.

04:40 Cool! So, what we want to do, additionally to building out this template in the next video, is we want to be able to access these projects, because currently, I’m not passing them forward, right? All I’m passing forward is the request object and the name of the template.

04:56 How you do that in Django is as a third argument in here, you can simply pass a dictionary. So, I’m going to give this a key called 'projects',

05:11 and as a value, I’m going to give what we got returned from our database, so this projects variable. I’m going to pass it here with the name 'projects'.

05:22 Just to make it easy, I’m naming them the same. And I’m going to get rid of this print() statement, because we don’t need it. So what I’m doing here now, inside of this view, is it’s going to get called when the user accesses this page.

05:37 Yes? Then, all the code in here runs, every time that the user accesses this page. I’m going to make a call to our database and retrieve all the Project objects that are stored in there. And finally, I’m going to return a render() call that takes the request, takes the name of the template that I want rendered, and passes these objects that we retrieved from the database forward to the template as well.

06:01 Because then, in the template, inside of a Django template, we’re going to be able to render these objects. So, let’s go ahead and do that in the next video where we’ll create our template and make sure that we’re actually displaying what we got from the database.

06:16 See you there!

reblark on March 10, 2020

In the bit about using the print command as a debugging tool, when I refreshed the page, the results in the terminal window had two lines <QuerySet [<Project: Project object (1)>]>

It seems like Python must have printed the code line: projects = Project.objects.all() just prior to the print statement. Yes?

Martin Breuss RP Team on March 11, 2020

Sounds to me like you might be using print() on the queryset somewhere in your views.py file.

That would explain why it prints out to your console when you make a request on your browser (i.e. refresh the page).

R morel on May 4, 2020

def all_projects(requests): return render(requests, ‘projects/all_projects.html’)

Scretch on June 14, 2020

I really like your approach of building by errors. I am definitely one to cringe when that happens but you make a good argument of learning from these messages. I imagine dark times when devs didn’t have that in the early days and had to find the errors manually. Oof....

Martin Breuss RP Team on June 15, 2020

👆👆👆👆👆👆👆 ❗️❗️❗️❗️❗️ 👆👆👆👆👆👆👆

Totally, good point! So thanks to all the previous-time-devs for the work on making nice error messages for us! 🤓

shaundefrancia on Aug. 31, 2020

This is where I got stuck. Please help.

Page not found (404)
Request Method: GET
Request URL:    http://127.0.0.1:8000/
Using the URLconf defined in portfolio.urls, Django tried these URL patterns, in this order:

admin/
projects/
The empty path didn't match any of these.

You’re seeing this error because you have DEBUG = True in your Django settings file. Change that to False, and Django will display a standard 404 page.

Martin Breuss RP Team on Aug. 31, 2020

Hi @shaundefrancia

Looks like you went to the following URL path in your browser:

Request URL:    http://127.0.0.1:8000/

Check what Django is telling you related to this:

Django tried these URL patterns, in this order:

admin/
projects/
The empty path didn't match any of these.

Do you have an idea what you could try to do next?

bogdanchira on Oct. 6, 2020

Hi,

I did not quite get what the dictionary part do and how you use it?

Bartosz Zaczyński RP Team on Oct. 6, 2020

@bogdanchira That dictionary, called a context, is a means for passing arbitrary data to a Django template. In this case, the template file is named all_projects.html, and the only data you’re exposing to that template is a collection of Project objects read from the database.

You can refer to the attributes defined in the context from your template, e.g.

{% for project in projects %}
    <p>{{ project.description }}</p>
    <p>{{ project.title }}</p>
{% endfor %}

Socorro Dominguez on July 24, 2024

I am following through and I think that maybe Django has been updated so, there is a new friend when trying the code above:

raise AppRegistryNotReady("Apps aren't loaded yet.")

I went to stack overflow and found that I should add:

import django
django.setup()

in the settings.py file. But even after I do that, then I get this error:

    raise RuntimeError(
RuntimeError: Model class projects.models.Project doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS.

I am not sure what it means by an app_label - I do have the projects in my settings.py file in the installed apps list…

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