I have three models below. I omit some irrelative fields.
class Team(models.Model):
name = models.CharField(max_length=100)
class Player(models.Model):
name = models.CharField(max_length=100)
class Match(models.Model):
home = models.ForeignKey(Team)
away = models.ForeignKey(Team)
home_players = models.CharField(max_length=100, null=True)
away_players = models.CharField(max_length=100, null=True)
home_players and away_players have the type of player id list, such as [1,2,3,...,15].
I want to know better ways like using Foreign Key List.
Because, I have some troubles in manually inserting players IDs at Django Admin Page. It takes much time finding player name in Player() and matching player's ID. I guess the task would be easier if I can assign a certain relationship between Player() and Team().
That would be a many-to-many relationship.
https://docs.djangoproject.com/en/1.9/topics/db/examples/many_to_many/
class Match(models.Model):
home = models.ForeignKey(Team)
away = models.ForeignKey(Team)
home_players = models.ManyToManyField(Player)
away_players = models.ManyToManyField(Player)
Related
I am having a model structure like:
class user(models.Model):
name = models.CharField(max_length=100)
tasks = models.IntegerField(default=0)
class project(models.Model):
worker = models.ForeignKey(user, on_delete=models.CASCADE)
project_name = models.CharField(max_length=100)
class task(models.Model):
project = models.ForeignKey(project, on_delete=models.CASCADE)
task_name = models.CharField(max_length=150)
expected_date = models.DateField(auto_now=False,auto_now_add=False,)
actual_date = models.DateField(auto_now=False,auto_now_add=False,blank=True,null=True,)
I want to traverse through the task list and if actual date field is not null i.e. task completed then to update the tasks field in user class by 1. I have written the following code:
a = task.objects.filter(actual_date__isnull=False)
for x in a:
x.project.worker.tasks+=1
However this is not giving the desired result. What should I do?
You are not saving your object after modifying it - simply modifying the value doesn't write it to the database. Try this instead:
a = task.objects.filter(actual_date__isnull=False)
for x in a:
worker = x.project.worker
worker.tasks += 1
worker.save()
On a separate note you should consider following PEP8 conventions and using CamelCase for your class names. As it is currently you can very easily mix up classes with objects.
Lets say I have a blog and a class user in a model. Furthermore I have a class comment connected with a foreign key.
class User(models.Model):
UserName = models.CharField(max_length=50, blank=True)
UserCountry = models.CharField(max_length=2, blank=True)
class Comment(models.Model):
commentText = models.TextField(max_length=1000)
commentSub = models.ForeignKey(User, related_name='comLink')
created_at = models.DateTimeField(auto_now_add=True)
Now I want to make an csv export in model admin and a I have a queryset with values_list.
I am wondering whether there exists a possibility to get each User once and e.g. only the last comment?
myList = queryset.values_list('UserName', 'UserCountry', 'comLink__commentText')
comLink is the related name. Now I just want the last comment. A timestamp is existing and I have not figured out how to filter or reverse etc.
You can do it with Subquery, I don`t know your model design, so it would be approximately like that:
from django.db.models import OuterRef, Subquery
com = Comment.objects.filter(commentSub=OuterRef('pk')).order_by('-created_at')
myList = queryset.annotate(LastComment=Subquery(com.values('commentText')[:1]))
myList = myList.values_list('UserName', 'UserCountry', 'LastComment')
https://docs.djangoproject.com/en/2.0/ref/models/expressions/#subquery-expressions
My code looks something like this:
from django.db import models
from django.conf import settings
User = settings.AUTH_USER_MODEL
class Dish(models.Model):
name = models.CharField(max_length=200)
class Meal(models.Model):
name = models.CharField(max_length=200)
dishes = models.ManyToManyField(Dish)
The many-to-many dishes field will result in a database table called 'myapp_meal_dishes' being created that includes id, meal_id, and dish_id fields.
I would like to add a MealDishEater model that connects with that auto-generated table:
class MealDishEater(models.Model):
meal_dish = models.ForeignKey(MealDishes, on_delete=models.CASCADE)
eater = models.ForeignKey(User, on_delete=models.PROTECT)
ate_meal = models.BooleanField(default=False)
Of course, that doesn't work, because MealDishes is not defined. Is there a way to do this or do I have to create my own through table?
You can access the ManyToManyField intermediate model with the through attribute. So this should work:
class MealDishEater(models.Model):
meal_dish = models.ForeignKey(Meal.dishes.through, on_delete=models.CASCADE)
Personally, though, I always create explicit through models for ManyToManyFields rather than allowing such magic.
I have the following Models:
class Player(models.Model):
name = models.CharField(max_length=30)
class Achievement(models.Model):
name = models.CharField(max_length=30)
class UnlockedAchievement(models.Model):
achievement = models.ForeignKey(Achievement)
date = models.DateTimeField()
class PlayerAchievements(models.Model):
player = models.ForeignKey(Player)
unlocked_achievements = models.ManyToManyField(UnlockedAchievement, related_name="unlocked_achievements", blank=True, null=True)
With a PUT, I'm trying to resolve both the Player's foreign key as well as the nested relationship of all the Achievements. My JSON data effectively looks like this:
{"name":"playername",
"achievements":
{
"ach1":"timestamp",
"ach2":"timestamp",
}
}
What I can't figure out is the magic combination of which kinds of Serializers to use and, when using them, which serializer fields or nested Serializers to use to be able to resolve Players by name, and the unlocked achievements (and then their Achievement foreign keys) by providing a name.
In this case I don't have access to id numbers, hence why things are done by names.
Such a strange mixture it seems. Can anyone lend a hand? Thanks in advance!
You can use nested relationships to fully include the serialization of a related model:
class AchievementSerializer(serializers.ModelSerializer):
class Meta:
model = Achievement
class UnlockedAchievementSerializer(serializers.ModelSerializer):
achievement = AchievementSerializer(many=False)
class Meta:
model = UnlockedAchievement
class PlayerAchievementsSerializer(serializers.ModelSerializer):
unlocked_achievements = UnlockedAchievementSerializer(many=True)
class Meta:
model = PlayerAchievements
class PlayerSerializer(serializers.ModelSerializer):
player_achievements = PlayerAchievementsSerializer(many=False)
class Meta:
model = Player
Then just filter the Player object by name and serialize it.
I have to integrate a legacy design with my Django project and I am looking for some advice on using an intermediary. The existing design works but now I need to filter the Project by a third table.
In english - I have a Organization (Django) and which points to many Projects (Legacy). But all of the Project don't refer to that Organization. I have a third table ProjectMap which was build via a Trigger to address that. It corresponds the Organization.name to a project.
How do I glue this together in order allow me to do this.
projects = Organization.objects.get(pk=1).projects.all()
And it won't get ALL of the projects just the ones which match in the third table. Here is what I have so far..
By the way if anyone has a better strategy I'm all ears
class Organization(models.Model):
name = models.CharField(max_length=32)
projects = models.ManyToManyField(Project)
class Project(models.Model):
"""This is the project info page..
Note: 'id' does exist and is the pk.
"""
result_number = models.IntegerField(null=True, db_column='LBLDGRUNNO', blank=True)
building_number = models.IntegerField(db_column='LBLDGNO')
name = models.CharField(max_length=150, db_column='SPIBLGNAME', blank=True)
class Meta:
db_table = u'PROJINFO'
managed = False
class ProjectMap(models.Model):
projinfo_table_id = models.IntegerField(null=True) # 'id' of Project
name = models.CharField(max_length=128, null=True) # 'name' in Organization
Thanks so much!
Not sure if this is what your asking, but you can use the through call on the ManyToManyField to define an intermediate table:
class Organization(models.Model):
name = models.CharField(max_length=32)
projects = models.ManyToManyField(Project, through="ProjectOrganisation")
class Project(models.Model):
#Stuff Here
class ProjectOrganisation(models.Model):
project = models.ForeignKey(Project)
organization = models.ForeignKey(Organization)
#Other Fields Here
Django does this automatically with manytomany fields anyway, just if you want to add extra fields, this is the way to do it.