I have a django model that looks something like
class Person(models.Model):
name = models.CharField(max_length=100)
favorite_color = models.CharField(max_length=100)
favorite_candy = models.CharField(max_length=100)
and I want to make a template model for it. Basically, I want a model that can have an arbitrary amount of Person's fields filled out. For instance, say I wanted to have a template for Person that likes chocolate - I'd say something like chocolate_template = PersonTemplate(favorite_color='chocolate') and if I wanted someone whose name is Gerald, I could say gerald_template = PersonTemplate(name='Gerald'). The thought is that I could use these template objects to later pre-fill a Person creation form.
My main question is an implementation question. It's totally possible for me to make a template like so
class PersonTemplate(models.Model):
name = models.CharField(max_length=100, blank=True)
favorite_color = models.CharField(max_length=100, blank=True)
favorite_candy = models.CharField(max_length=100, blank=True)
but the code is horrible in that I have to manually copy-paste the contents of the Person class. This means that if I change Person, I have to remember to update PersonTemplate. I was wondering if there's a prettier way to make a 'child' of a model where all of the fields are optional. Setting all of the fields of Person to blank=True and adding an isTemplate field is also a no-no because Person and PersonTemplate should be two different entities in the database. Any thoughts on this?
Yes of course :)
class PersonTemplate(Person):
field = models.CharField(max_length=100, blank=True)
Its mean you have every fields from Person and you can add more specific fields for PersonTemplate
class Person(models.Model):
Already extend from Model, its why you have access to created, modified, id, pk....
What is good its PersonTemplate 'extend' Person who 'extend' Model.
Since Django 1.10 you can overrride field like that :
class PersonTemplate(Person):
favorite_color = models.CharField(max_length=100, blank=True)
favorite_candy = models.CharField(max_length=100, blank=True)
Related
I have the Goal Model and every Goal can have one Mastergoal and or multiple Subgoals.
Goals are connected with Links and every Link can have a different weight.
How do I achieve this with Django?
What I've got so far:
class Goal(models.Model):
user = models.ForeignKey(CustomUser, related_name='goals', on_delete=models.CASCADE)
name = models.CharField(max_length=300)
sub_goals = models.ManyToManyField(to='self', through='Link', symmetrical=False, related_name='master_goals')
class Link(models.Model):
master_goal = models.ForeignKey(Goal, on_delete=models.CASCADE, related_name="sub_links")
sub_goal = models.OneToOneField(Goal, on_delete=models.CASCADE, related_name="master_links")
weight = models.PositiveSmallIntegerField(default=1)
I can't just add an ForeignKey Field on Goal to itself, because every Link can have a different weight.
The solution I've got now works, but it feels wrong. I want to be able to access a Goal's Mastergoal like this: goal.master_goal
I have been tasked with creating Django Models for a hypothetical apartment booking application.
My question is: can I use a model that I've defined, as a field in another model?
For example, I will have one model called "Listing" that represents an apartment being listed.
class Listing(models.Model):
address = models.IntegerField()
owner = models.CharField(max_length=256)
duration = models.DurationField()
price= models.IntegerField()
I also want to have a "Booking" model that represents an apartment once someone has booked it. It will have the exact same info as a Listing, with the addition of the username of the person who booked it. So can I have my Booking model use Listing as a field? And then just have one extra field for the booker's username.
Any other tips/critiques are highly appreciated as I am a complete beginner at Django.
I'm not 100% sure what you mean by use Listing as a field
But to me, you should be looking at the different built-in model relationships that exist in Django.
In your particular case, you will probably want to use a One-to-One relationship like so,
class Listing(models.Model):
address = models.IntegerField()
owner = models.CharField(max_length=256)
duration = models.DurationField()
price= models.IntegerField()
class Booking(models.Model):
listing= models.OneToOneField(
Listing,
on_delete=models.CASCADE,
)
username = models.Charfield()
Now if a user can book more than one apartment at a time, you'll be interested in a ForeignKey relationship like so,
class Listing(models.Model):
address = models.IntegerField()
owner = models.CharField(max_length=256)
duration = models.DurationField()
price= models.IntegerField()
class Booking(models.Model):
listing= models.ForeignKey(
Listing,
on_delete=models.CASCADE,
)
username = models.Charfield()
Note that in both examples I used Charfield for the username, feel free to use whatever Django field you need.
The concept of a model as field is odd. What you can do is establish relationships between models, or to inherit one from the other. Given your situation, you can maybe inherit Booking from Listing:
The docs on this topic.
You'll have something like this:
class Listing(models.Model):
address = models.IntegerField()
owner = models.CharField(max_length=256)
duration = models.DurationField()
price= models.IntegerField()
class Booking(Listing):
#your new fields
I am using Django REST Framework. I have two models, Sites and Statuses.
class Sites(models.Model):
site_id = models.AutoField(primary_key=True)
status = models.ForeignKey(Statuses, models.DO_NOTHING, blank=True, null=True)
class Statuses(models.Model):
status_id = models.AutoField(primary_key=True)
description = models.CharField(max_length=255, blank=True, null=True, unique=True)
class Meta:
managed = True
db_table = 'Statuses'
I would like to be able to perform a GET on sites, and have the Statuses.description field returned (instead of Statuses.status_id). Also, I would like it so that either status_id or description may be used interchangeably in a POST to create a new site. Where does this type of functionality belong (serializer, models, etc...)?
I know I can accomplish the first part of my question by adding a property to the Sites model and then referencing this field in the Sites serializer.
#property
def status(self):
return self.row_status.description
However I thought the convention of a Model is that it should be a 1:1 representation of the database table. Is there a better way to do this?
This fits well in the serializer, like this:
class SitesSerializer(serializers.ModelSerializer):
description = serializers.CharField(source='status.description')
class Meta:
model = Sites
fields = ('site_id', 'description')
(But the status field should probably not have null=True set.)
Using the django-rest-framework is it possible to retrieve content from a related field. So for example I want to create a genre list which contains all projects within it. This is what I have but I keep on getting the error:
'Genre' object has no attribute 'project_set'
models.py
class Genre(models.Model):
name = models.CharField(max_length=100, db_index=True)
class Project(models.Model):
title = models.CharField(max_length=100, unique=True)
genres = models.ManyToManyField(Genre, related_name='genres')
serializers.py
class GenreSerializer(serializers.ModelSerializer):
project_set = serializers.ManyRelatedField()
class Meta:
model = Genre
fields = ('name', 'project_set')
The related name you're using on the Project class is badly named. That related name is how you access the set of projects related to a given genre instance. So you should be using something like related_name='projects'. (As it is you've got it the wrong way around.)
Then make sure that your serializer class matches up with the related name you're using, so in both places project_set should then instead be projects.
(Alternatively you could just remove the related_name='genres' entirely and everything will work as you were expecting, as the default related_name will be 'project_set'.)
I have this setup in my models:
class Author(models.Model):
name = models.CharField(max_length=100)
class Topic(models.Model):
name = models.CharField(max_length=100)
class Article(models.Model):
name = models.CharField(max_length=100)
authors = models.ManyToManyField(Author, null=True, blank=True)
topics = models.ManyToManyField(Topic, null=True, blank=True)
Given an author, I want to know which topics he wrote about:
def author_info(request, pk):
author = get_object_or_404(Author, pk=pk)
topics = ????
If I had specified a through field, I could use that, but now Django makes the through field for me, and since its supposed to be transparent, Id rather not reference the field (unless there is a proper Django construction for that).
Use Lookups that span relationships:
topics = Topic.objects.filter(article__authors=author).distinct()
Note: you have to use distinct here, because the same topic can be selected by different articles.