2020-04-01 Created: windows10 / Python-3.8.2-amd64 / Django-3.0.4
There isn't much information in Japanese about Django's foreign keys online either. But usually, "favorite food" and "address book" should be different apps, I think that how to use foreign keys is a basic compulsory item.
For foreign keys in the same database and to foreign databases I have created a simple tutorial. For those who want to easily know how to correlate multiple databases with each other.
--Cat management app cafe for cat cafes --Create a table with the name of the cat and a table with your favorite food, and associate them with a foreign key. --Cat address book app negura --Create a database of cats. Called by a foreign key from the cafe app.
If you're new to Django, read the basic tutorial first. Practical tutorial on Django in 10 minutes
Create a new project by executing the following in the place where you want to put the source.
django-admin startproject mysite
Enter the created directory mysite and create two new applications.
cd mysite
python manage.py startapp cafe
python manage.py startapp sumika
The arrangement of the files so far is like this
mysite/
mysite/
__pycashe__/ <-do not worry about
setting.py, urls.py etc.*.5 py
neko/
migrations/ <-do not worry about
models.py, views.py etc.*.6 py
sumika/
migrations/ <-do not worry about
models.py, views.py etc.*.6 py
manage.py
Register two apps, cafe and negura.
mysite/mysite/settings.py
INSTALLED_APPS = [
'cafe.apps.CafeConfig',
'negura.apps.NeguraConfig',
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
]
mysite/mysite/urls.py
from django.contrib import admin
from django.urls import path, include
urlpatterns = [
path('cafe/', include('cafe.urls')),
path('negura/', include('negura.urls')),
path('admin/', admin.site.urls),
]
neko_food is a foreign key in the same database in the cafe app neko_negura is a foreign key to the negura app, that is, another database of the next app.
The def __str__ (self): method is usually needed in django's generic views when using ForeignKey.
If you do not override this method, it will appear in your browser
The instance name is displayed as food_name.object (1) instead of sanma.
Thanks to this method, the string is displayed in the pull-down list when using CreateView or FormView.
neko_negura is pulling the model from an outside app, so
Call the model after prefixing the app name with negura.NeguraModel.
mysite/cafe/models.py
from django.db import models
from negura.models import NeguraModel
class NekoModel(models.Model):
neko_name = models.CharField(max_length = 20)
neko_food = models.ForeignKey('FoodModel', null = True,on_delete = models.SET_NULL)
neko_negura = models.ForeignKey('negura.NeguraModel', null = True,on_delete = models.SET_NULL)
class FoodModel(models.Model):
food_name = models.CharField(max_length = 20)
def __str__(self):
return self.food_name
Don't get confused about which view uses which template It has a terrible file name.
mysite/cafe/views.py
from django.views import generic
from .models import NekoModel, FoodModel
class NekoListView(generic.ListView):
model = NekoModel
context_object_name = 'nekolistview_context'
template_name = 'cafe/nekolistview_template.html'
class NekoCreateView(generic.CreateView):
model = NekoModel
context_object_name = 'nekocreateview_context'
template_name = 'cafe/nekocreateview_template.html'
fields = ['neko_name', 'neko_food', 'neko_negura']
success_url = '/cafe/nekolist_url'
class FoodListView(generic.ListView):
model = FoodModel
context_object_name = 'foodlistview_context'
template_name = 'cafe/foodlistview_template.html'
urls.py creates a new file I've given it a crappy name so I don't get confused about which pathname points to which view.
mysite/cafe/urls.py
from django.urls import path
from . import views
urlpatterns = [
path('nekolist_url', views.NekoListView.as_view(), name = 'nekolistview_path'),
path('nekocreate_url', views.NekoCreateView.as_view(), name = 'nekocreateview_path'),
path('foodlist_url', views.FoodListView.as_view(), name = 'foodlistview_path'),
]
I will not create a view for entering food and address because it will take a lot of tutorial work. Edit and enable admin.py for input from the admin screen instead.
mysite/cafe/admin.py
from cafe.models import NekoModel, FoodModel
from django.contrib import admin
admin.site.register(NekoModel)
admin.site.register(FoodModel)
Create 3 templates. I put it in the default directory, but I don't really like it because the hierarchy is too deep.
mysite/cafe/template/cafe/nekolistview_template.html
<h1>Ichiran the cat</h1>
<table>
{% for neko_param in nekolistview_context %}
<tr>
<td>{{ neko_param.neko_name }}</td>
<td>{{ neko_param.neko_food.food_name }}</td>
<td>{{ neko_param.neko_negura.negura_name }}</td>
</tr>
{% endfor %}
</table>
<p><a href = "{% url 'foodlistview_path' %}">Cat food</a></p>
<p><a href = "{% url 'neguralistview_path' %}">Cat roost</a></p>
<p><a href = "{% url 'nekocreateview_path' %}">Cat</a></p>
mysite/cafe/template/cafe/foodlistview_template.html
<h1>Cat food</h1>
<table>
{% for food_param in foodlistview_context %}
<tr>
<td>{{ food_param.food_name }}</td>
</tr>
{% endfor %}
</table>
<p><a href = "{% url 'nekolistview_path' %}">Ichiran the cat</a></p>
mysite/cafe/template/cafe/nekocreateview.html
<h1>Cat</h1>
<form method = "post">
{% csrf_token %}
{{ form.as_p }}
<input type = "submit" value = "Toro" />
</form>
<p><a href = "{% url 'nekolistview_path' %}">Ichiran the cat</a></p>
Basically, it's a repetition of what I did at the cafe.
mysite/negura/models.py
from django.db import models
class NeguraModel(models.Model):
negura_name = models.CharField(max_length = 20)
def __str__(self):
return self.negura_name
mysite/negura/views.py
from django.views import generic
from .models import NeguraModel
class NeguraListView(generic.ListView):
model = NeguraModel
context_object_name = 'neguralistview_context'
template_name = 'negura/neguralistview_template.html'
mysite/negura/urls.py
from django.urls import path
from . import views
urlpatterns = [
path('neguralist_url', views.NeguraListView.as_view(), name = 'neguralistview_path'),
]
mysite/negura/admin.py
from cafe.models import NeguraModel
from django.contrib import admin
admin.site.register(NeguraModel)
Create one template The location is the default location.
mysite/negura/template/negura/neguralistview_template.html
<h1>Cat roost</h1>
<table>
{% for negura_param in neguralistview_context %}
<tr>
<td>{{ negura_param.negura_name }}</td>
</tr>
{% endfor %}
</table>
<p><a href = "{% url 'nekolistview_path' %}">Ichiran the cat</a></p>
After migrating, create an administrator for the admin site and Make the admin screen accessible.
python manage.py makemigrations
python manage.py migrate
python manage.py createsuperuser
Start the development server. The port number is 8000 because it is started by default.
python manage.py runserver
Access the following with a browser to display the admin screen. "Eat" and "Sumika" cannot be entered directly with this app, so enter them from the admin screen.
http://localhost:8000/admin/
For example, food is "Saury" and "Crispy", and Sumika is "Danboru" and "Moufu".
Enter the following to get a list of cats. At first, there are no registered cats, so they are not on the table.
http://localhost:8000/neko/
When you enter the registration screen from the "Cat Touroku" link, Enter the cat's name in the form and "Food" and "Negura" can be selected from the drop-down list.
The end
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