Create a forum application using django #11: URL Behavior and Updat...

Repository

https://github.com/python

What Will I Learn?

URL Behavior
Update View and Edit Menu

Requirements

Basic Python
Install Python 3
Install Django

Resources

Python - https://www.python.org/
Django- https://www.djangoproject.com/
Bootstrap 4 - https://getbootstrap.com/docs/4.0/getting-started/introduction/

Difficulty

Basic

Tutorial Content

We will continue with the application tutorial forums that we have created so far. a lot has been done in this tutorial. there are some important things that you should not miss it. I suggest you follow the previous tutorial in the curriculum section. In the previous tutorial, we learned how to make detailed views and also learn how to pass parameters to a class view by using the get_context_data () method. Now in this tutorial I will update view and edit view. but before that, I will give you tricks and suggestions regarding the importance of the order of URLs on views.py

URL Behavior

There are some problems when we want to create a URL with dynamic parameters. as happened in the previous tutorial we used Slug on our URL. For more details, we can see forums/views.py:

We can see in the example image above, the URL with the slug parameter is in the first path position. Of course, this slug value will be dynamic. On the other hand, we also have a URL with the first path being 'add/'.

Of course, this will be ambiguous. Because the URL system will recognize that the 'add /' path is also part of the slug parameter in the path <slug: slug>/ and when this application is run we will see an error like the picture below:

This error message appears because the Django URL system recognizes 'add/' as a Slug parameter. to solve this problem we need to recognize the behavior of the system URL in Django. In Django, the URL order is very important. URL order can be a priority on the system to read the URL. For more details we can see the code:

from django.urls import path
from .views import ForumCreate, ForumListView, ForumUserListView, ForumDetailView

urlpatterns = [
    path('', ForumListView.as_view(), name='forum-list'),
    path('add/', ForumCreate.as_view(), name='forum-add')
    path('/', ForumDetailView.as_view(), name='forum-detail'),
    path('by//', ForumUserListView.as_view(), name='forum-by'),
]

I will move the path path('', ForumListView.as_view(), name='forum-list') above path('<slug:slug>/', ForumDetailView.as_view(), name='forum-detail'),. Now you can eliminate the error message that appears earlier:

ezgif.com-video-to-gif.gif

And the problem has been resolved, now you have understood the behavior of the URL system in Django.

Update View

Now we go to Update view. Of course, data updates are common in an application. in Django, we have our own way to update our data. for more details, just go ahead and create the URL and create a class view that we will use in this update system:

forums/urls.py

from django.urls import path
from .views import ForumCreate, ForumListView, ForumUserListView, ForumDetailView, ForumUpdateView // import class ForumUpdateView

urlpatterns = [
    path('', ForumListView.as_view(), name='forum-list'),
    path('add/', ForumCreate.as_view(), name='forum-add'),
    path('edit/', ForumUpdateView.as_view(), name='forum-edit'), //Define URL edit/update
    path('/', ForumDetailView.as_view(), name='forum-detail'),
    path('by//', ForumUserListView.as_view(), name='forum-by'),
]

The first step we have to do is import the class view that we will use. here I will give the name ForumUpdateView, make sure the name you give is relevant to the usefulness of the class.
then you can use the class that you imported to use in the path path('edit/<int:pk>', ForumUpdateView.as_view(), name='forum-edit'). In this path we will pass one additional parameter after editing, the parameter is type integer and primary key edit/<int:pk>. Later on, we will pass the ID from each forum id and don't forget to give an alias so that we can more easily call later name='forum-edit'.

Now we switch to forums/views.py, We imported the ForumUpdateView class. But we haven't defined it in views.py class for that we will define it as follows:

from django.shortcuts import render, get_object_or_404
from django.views.generic import CreateView, ListView, DetailView, UpdateView
from .models import Forum
from django.contrib.auth.models import User
from django.contrib.auth.decorators import login_required
from django.utils.decorators import method_decorator

class ForumUpdateView(UpdateView):
    model = Forum
    fields = ['title','desc']

The code above is a code snippet because what we will discuss is only in the ForumUpdateView class.

In the ForumUpdateView class, we will use UpdateView as a parameter class ForumUpdateView(UpdateView). UpdateView is a generic class that has been provided by Django. We have discussed the generic class in the previous tutorial,
In this class we will use the Forum model model = Forum, that we imported above from .models import Forum. Then we can define any fields that we will update. Here I will only update two fields, namely title and desc fields = ['title','desc'].
Restrict access to edit view

Of course, not just anyone will be allowed to edit data. there are different conditions for each application. well in this forum application we don't allow other users to edit other user forums. So the user can only edit the contents of their own forum. We need a button as an interface to go to the edit URL. I will appear on the interface at forum_detail.html.

forums/forum_detail.html

{% extends "base.html" %}

{% load humanize %}

{% block title %} {{object.title}} {% endblock %}

{% block content %}
<div class="jumbotron">
  <h1>{{object.title}}</h1>
  {% if request.user == object.user %} // only the user who created the forum
  <a href="{% url 'forum-edit' object.id %}">Edit</a>
  {% endif  %}
  <p style="font-size: 20px;">{{ object.desc }}</p>
  - <span><i>{{object.created_at | naturaltime}}</i></span>
  <p>{{additional}}</p>
</div>
{% endblock%}

to limit it we can compare the value of request.user with object.user. If the result is the same or true. then <a> tag will appear and we can click it to go to the edit menu. We can access the user who is logged on the request object and for data from forums we can take from object values.
Then in the <a> tag, we will render the URL for the forum edit menu <a href="{% url 'forum-edit' object.id %}">Edit</a>. to render it we can call the alias if you still remember the alias name of the edit URL is 'forum-edit' and for the parameters, we can take it from object.id.

If there is no error, then we can see the results as shown below, I will log in with an admin account as milleaduski.

ezgif.com-video-to-gif (1).gif

In accordance with the expectations that we have expected. We cannot edit forums that are not ours. Here I can't edit the forums owned by user milleaduski1994. because I logged in as milleaduski.

Edit Menu

now we will enter the edit section of the forum. In this section we will learn how to edit forum data and not only that, we will also learn new things, set templates that we will render in the ForumUpdateView class. For more details, we can see the code below:

forums/views.py

class ForumUpdateView(UpdateView):
    model = Forum
    fields = ['title','desc']
    template_name = 'forums/forum_update_form.html' // set template

To set up templates is very easy. we only need key template_name and then the name of the template directory that will be rendered 'forums/forum_update_form.html'.

Keep in mind we have set our template directory in the previous tutorial. the following picture will explain it briefly:

Create view forum_update_form.html

Now we will create a view for the forum edit menu. This is not much different from the menu add forums. For more details, we can see in the example below:

forums/forum_update_form.html

{% extends "base.html" %}

{% block title %} Edit Forum {% endblock %}

{% block content %}
<h2>Edit Forum</h2>
<form method="post">
    {% csrf_token %}
    {{ form.as_p }}
    <button type="submit" name="button">Update</button>
</form>

{% endblock%}

{{ form.as_p }} will render the form that we define automatically, this is a function that has been provided by Django. If there is no error then we can see the results like the demonstration below:

ezgif.com-video-to-gif (2).gif

Now we can see in the picture above, we have successfully updated the forum data and the update menu can only be accessed by the user who created the forum.