<DJANGO>[MODEL]

[Model]

1. 기본 구조

#django.db.models.Model
from django.db import models
 
class Person(models.Model):
    first_name = models.CharField(max_length=30) 
    last_name = models.CharField(max_length=30)

 - app 생성

 - models.py에서 django.db.models을 import

 - Model을 상속

 - models 내부의 각각 Field 함수로 컬럼 설정

 - settings.py의 INSTALLED_APPS에 생성한 app을 추가

 - manage.py migrate 실행

 - manage.py makemigrations 실행

2. 기본 Filed

from django.db import models
 
class Musician(models.Model):
    first_name = models.CharField(max_length=50) 
    last_name = models.CharField(max_length=50) 
    instrument = models.CharField(max_length=100)
 
class Album(models.Model):
    artist = models.ForeignKey(Musician, on_delete=models.CASCADE) 
    name = models.CharField(max_length=100)
    release_date = models.DateField()
    num_stars = models.IntegerField()

3. Filed Options

 - null : (default=False) True 일때, 값이 없으면 null 등록

 - blank : (default=False) True 일때, 값이 없으면 그대로 빈값 등록 <주의 : 전달파라미터 확인해야함>

 - choices : 튜플로 작성된 key와 value를 컬럼에 매핑. key를 입력 받고 get_shirt_size_display()로 value를 확인 할 수 있다.

YEAR_IN_SCHOOL_CHOICES = ( 
    ('FR', 'Freshman'), 
    ('SO', 'Sophomore'), 
    ('JR', 'Junior'), 
    ('SR', 'Senior'), 
    ('GR', 'Graduate'),
)

from django.db import models
 
class Person(models.Model): 
    SHIRT_SIZES = (
        ('S', 'Small'),
        ('M', 'Medium'),
        ('L', 'Large'),
    )
    name = models.CharField(max_length=60)
    shirt_size = models.CharField(max_length=1, choices=SHIRT_SIZES)

>>> p = Person(name="Fred Flintstone", shirt_size="L") 
>>> p.save()
>>> p.shirt_size
'L'
>>> p.get_shirt_size_display() 
'Large'

 - default : 값이 없을 경우 기본 값을 설정

 - help_text : form widget에서 help로 확인할 수 있는 정보 ( 문서 작성 시 유용함 )

 - primary_key : True 일때, primary key로 설정 됨 (django의 기본 primary key는 "id" 컬럼)

from django.db import models
 
class Fruit(models.Model):
    name = models.CharField(max_length=100, primary_key=True)

>>> fruit = Fruit.objects.create(name='Apple') 
>>> fruit.name = 'Pear'
>>> fruit.save()
>>> Fruit.objects.values_list('name', flat=True) 
['Apple', 'Pear']

id = models.AutoField(primary_key=True)

 - unique : null이 1회 가능한 컬럼으로 설정

4. Verbose field names

 - Field를 파악할 수 있는 이름

 - default : field 이름

first_name = models.CharField(max_length=30)

 - 설정

first_name = models.CharField("person's first name", max_length=30)

 - ForeignKey, ManyToManyField, OneToOneField는 필요함

poll = models.ForeignKey( 
    Poll,
    on_delete=models.CASCADE,
    verbose_name="the related poll", 
)
sites = models.ManyToManyField(Site, verbose_name="list of sites") 
place = models.OneToOneField(
    Place, 
    on_delete=models.CASCADE, 
    verbose_name="related place",
)

5. 1:1 관계

from django.db import models
 
class Place(models.Model):
    name = models.CharField(max_length=50) 
    address = models.CharField(max_length=80)
    def __str__(self):
        return "%s the place" % self.name
 
class Restaurant(models.Model): 
    place = models.OneToOneField(
        Place, 
        on_delete=models.CASCADE, 
        primary_key=True,
    )
    serves_hot_dogs = models.BooleanField(default=False) 
    serves_pizza = models.BooleanField(default=False)
    def __str__(self):
        return "%s the restaurant" % self.place.name
 
class Waiter(models.Model):
    restaurant = models.ForeignKey(
        Restaurant, 
        on_delete=models.CASCADE
    ) 
    name = models.CharField(max_length=50)
    def __str__(self):
        return "%s the waiter at %s" % (self.name, self.restaurant)

###
>>> p1 = Place(name='Demon Dogs', address='944 W. Fullerton') 
>>> p1.save()
>>> p2 = Place(name='Ace Hardware', address='1013 N. Ashland') 
>>> p2.save()
 
###
>>> r = Restaurant(place=p1, serves_hot_dogs=True, serves_pizza=False) 
>>> r.save()
 
###
>>> r.place
<Place: Demon Dogs the place>
 
###
>>> p1.restaurant
<Restaurant: Demon Dogs the restaurant>
 
###
>>> from django.core.exceptions import ObjectDoesNotExist 
>>> try:
>>> p2.restaurant
>>> except ObjectDoesNotExist:
>>> print("There is no restaurant here.") 
There is no restaurant here.
 
###
> hasattr(p2, 'restaurant')
False
 
###
>>> r.place = p2
>>> r.save()
>>> p2.restaurant
<Restaurant: Ace Hardware the restaurant> 
>>> r.place
<Place: Ace Hardware the place>
 
###
>>> p1.restaurant = r
>>> p1.restaurant
<Restaurant: Demon Dogs the restaurant>
 
###
>>> p3 = Place(name='Demon Dogs', address='944 W. Fullerton')
>>> Restaurant.objects.create(place=p3, serves_hot_dogs=True, serves_pizza=False) 
Traceback (most recent call last):
...
ValueError: save() prohibited to prevent data loss due to unsaved related object 'place'.
 
###
>>> Restaurant.objects.all()
<QuerySet [<Restaurant: Demon Dogs the restaurant>, <Restaurant: Ace Hardware the restaurant>]>
 
 
###
>>> Place.objects.order_by('name')
<QuerySet [<Place: Ace Hardware the place>, <Place: Demon Dogs the place>]>
 
###
>>> Restaurant.objects.get(place=p1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.get(place__pk=1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.filter(place__name__startswith="Demon") 
<QuerySet [<Restaurant: Demon Dogs the restaurant>]>
>>> Restaurant.objects.exclude(place__address__contains="Ashland") 
<QuerySet [<Restaurant: Demon Dogs the restaurant>]>
 
###
>>> Place.objects.get(pk=1)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant__place=p1)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant=r)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant__place__name__startswith="Demon") 
<Place: Demon Dogs the place>
 
###
>>> w = r.waiter_set.create(name='Joe')
>>> w
<Waiter: Joe the waiter at Demon Dogs the restaurant>
 
###
>>> Waiter.objects.filter(restaurant__place=p1)
<QuerySet [<Waiter: Joe the waiter at Demon Dogs the restaurant>]>
>>> Waiter.objects.filter(restaurant__place__name__startswith="Demon") 
<QuerySet [<Waiter: Joe the waiter at Demon Dogs the restaurant>]>
 

6. 1대n 관계

from django.db import models
 
class Manufacturer(models.Model): 
    # ...
    pass
class Car(models.Model):
    manufacturer = models.ForeignKey(Manufacturer, on_delete=models.CASCADE) 
    # ...

class Car(models.Model):
    company_that_makes_it = models.ForeignKey(
        Manufacturer, 
        on_delete=models.CASCADE,
    )
    # ...

 - 예제

from django.db import models
 
class Reporter(models.Model):
    first_name = models.CharField(max_length=30) 
    last_name = models.CharField(max_length=30) 
    email = models.EmailField()
 
    def __str__(self):
        return "%s %s" % (self.first_name, self.last_name)
 
class Article(models.Model):
    headline = models.CharField(max_length=100)
    pub_date = models.DateField()
    reporter = models.ForeignKey(Reporter, on_delete=models.CASCADE)
 
    def __str__(self): 
        return self.headline
    class Meta:
        ordering = ('headline',)

>>> r = Reporter(first_name='John', last_name='Smith', email='john@example.com') 
>>> r.save()
>>> r2 = Reporter(first_name='Paul', last_name='Jones', email='paul@example.com') 
>>> r2.save()

###
>>> from datetime import date
>>> a = Article(id=None, headline="This is a test", pub_date=date(2005, 7, 27), reporter=r) 
>>> a.save()
>>> a.reporter.id 1
>>> a.reporter 
<Reporter: John Smith>
 
###
>>> r3 = Reporter(first_name='John', last_name='Smith', email='john@example.com') 
>>> Article.objects.create(headline="This is a test", pub_date=date(2005, 7, 27), reporter=r3)
Traceback (most recent call last):
...
ValueError: save() prohibited to prevent data loss due to unsaved related object 'reporter'.
 
###
>>> r = a.reporter
 
###
>>> new_article = r.article_set.create(headline="John's second story", pub_date=date(2005, 7, 29))
>>> new_article
<Article: "John's second story"> 
>>> new_article.reporter 
<Reporter: John Smith>
>>> new_article.reporter.id
1
 
###
>>> new_article2 = Article(headline="Paul's story", pub_date=date(2006, 1, 17)) 
>>> r.article_set.add(new_article2)
>>> new_article2.reporter
<Reporter: John Smith>
>>> new_article2.reporter.id
1
>>> r.article_set.all()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>
 
###
>>> r2.article_set.add(new_article2) >>> new_article2.reporter.id
2
>>> new_article2.reporter
<Reporter: Paul Jones>
 
###
>>> r.article_set.add(r2)
Traceback (most recent call last):
...
TypeError: 'Article' instance expected
>>> r.article_set.all()
<QuerySet [<Article: "John's second story">, <Article: This is a test>]> >>> r2.article_set.all()
<QuerySet [<Article: "Paul's story">]>
>>> r.article_set.count() 2
>>> r2.article_set.count() 1
 
###
>>> r.article_set.filter(headline__startswith='This') <QuerySet [<Article: This is a test>]>
# Find all Articles for any Reporter whose first name is "John".
>>> Article.objects.filter(reporter__first_name='John')
<QuerySet [<Article: "John's second story">, <Article: This is a test>]>
 
###
>>> Article.objects.filter(reporter__first_name='John')
<QuerySet [<Article: "John's second story">, <Article: This is a test>]>
 
###
>>> Article.objects.filter(reporter__first_name='John', reporter__last_name='Smith') 
<QuerySet [<Article: "John's second story">, <Article: This is a test>]>
 
###
>>> Article.objects.filter(reporter__pk=1)
<QuerySet [<Article: "John's second story">, <Article: This is a test>]> 
>>> Article.objects.filter(reporter=1)
<QuerySet [<Article: "John's second story">, <Article: This is a test>]> 
>>> Article.objects.filter(reporter=r)
<QuerySet [<Article: "John's second story">, <Article: This is a test>]>
>>> Article.objects.filter(reporter__in=[1,2]).distinct()
<QuerySet [<Article: "John's second story">, <Article: "Paul's story">, <Article: This is a test>]>
 
###
>>> Article.objects.filter(reporter__in=[r,r2]).distinct()
<QuerySet [<Article: John's second story>, <Article: Paul's story>, <Article: This is a test>]>
 
###
>>> Article.objects.filter(reporter__in=Reporter.objects.filter(first_name='John')).distinct()
<QuerySet [<Article: "John's second story">, <Article: This is a test>]>
 
###
>>> Reporter.objects.filter(article__pk=1) 
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article=1) 
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article=a) 
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article__headline__startswith='This')
<QuerySet [<Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>]> 
>>> Reporter.objects.filter(article__headline__startswith='This').distinct() 
<QuerySet [<Reporter: John Smith>]>
 
###
>>> Reporter.objects.filter(article__headline__startswith='This').count()
3
>>> Reporter.objects.filter(article__headline__startswith='This').distinct().count()
1
 
###
>>> Reporter.objects.filter(article__reporter__first_name__startswith='John') 
<QuerySet [<Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>, <Reporter: John Smith>]>
>>> Reporter.objects.filter(article__reporter__first_name__startswith='John').distinct()
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article__reporter=r).distinct() 
<QuerySet [<Reporter: John Smith>]>
 
###
>>> Article.objects.all()
<QuerySet [<Article: "John's second story">, <Article: "Paul's story">, <Article: This is a test>]>
>>> Reporter.objects.order_by('first_name')
<QuerySet [<Reporter: John Smith>, <Reporter: Paul Jones>]>
>>> r2.delete()
>>> Article.objects.all()
<QuerySet [<Article: "John's second story">, <Article: This is a test>]> 
>>> Reporter.objects.order_by('first_name')
<QuerySet [<Reporter: John Smith>]>
>>> Reporter.objects.filter(article__headline__startswith='This').delete() 
>>> Reporter.objects.all()
<QuerySet []>
>>> Article.objects.all()
<QuerySet []>

7. n대n 관계

from django.db import models
 
class Topping(models.Model): 
    # ...
    pass
 
class Pizza(models.Model): 
    # ...
    toppings = models.ManyToManyField(Topping)

 - 예제

from django.db import models 
 
class Publication(models.Model):
    title = models.CharField(max_length=30) 
    def __str__(self):
        return self.title 
    class Meta:
        ordering = ('title',)
 
class Article(models.Model):
    headline = models.CharField(max_length=100) 
    publications = models.ManyToManyField(Publication)
    def __str__(self): 
        return self.headline
    class Meta:
        ordering = ('headline',)

###
>>> p1 = Publication(title='The Python Journal') >>> p1.save()
>>> p2 = Publication(title='Science News')
>>> p2.save()
>>> p3 = Publication(title='Science Weekly') >>> p3.save()
 
###
>>> a1 = Article(headline='Django lets you build Web apps easily')
 
###
>>> a1.publications.add(p1)
Traceback (most recent call last):
...
ValueError: 'Article' instance needs to have a primary key value before a many-to-many relationship can be used.
 
###
>>> a1.save()
 
###
>>> a1.publications.add(p1)
 
###
>>> a2 = Article(headline='NASA uses Python') 
>>> a2.save()
>>> a2.publications.add(p1, p2)
>>> a2.publications.add(p3)
 
###
>>> a2.publications.add(p3)
 
###
>>> a2.publications.add(a1)
Traceback (most recent call last):
...
TypeError: 'Publication' instance expected
 
###
>>> new_publication = a2.publications.create(title='Highlights for Children')
 
###
>>> a1.publications.all()
<QuerySet [<Publication: The Python Journal>]>
>>> a2.publications.all()
<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>, <Publication: The Python Journal>]>
 
###
>>> p2.article_set.all()
<QuerySet [<Article: NASA uses Python>]>
>>> p1.article_set.all()
<QuerySet [<Article: Django lets you build Web apps easily>, <Article: NASA uses Python>]>
>>> Publication.objects.get(id=4).article_set.all() 
<QuerySet [<Article: NASA uses Python>]>
 
###
>>> Article.objects.filter(publications__id=1)
<QuerySet [<Article: Django lets you build Web apps easily>, <Article: NASA uses Python>]>
>>> Article.objects.filter(publications__pk=1)
<QuerySet [<Article: Django lets you build Web apps easily>, <Article: NASA uses Python>]>
>>> Article.objects.filter(publications=1)
<QuerySet [<Article: Django lets you build Web apps easily>, <Article: NASA uses Python>]>
>>> Article.objects.filter(publications=p1)
<QuerySet [<Article: Django lets you build Web apps easily>, <Article: NASA uses Python>]>
>>> Article.objects.filter(publications__title__startswith="Science")
<QuerySet [<Article: NASA uses Python>, <Article: NASA uses Python>]>
>>> Article.objects.filter(publications__title__startswith="Science").distinct() 
<QuerySet [<Article: NASA uses Python>]>
 
###
>>> Article.objects.filter(publications__title__startswith="Science").count() 2
>>> Article.objects.filter(publications__title__startswith="Science").distinct().count()
1
>>> Article.objects.filter(publications__in=[1,2]).distinct()
<QuerySet [<Article: Django lets you build Web apps easily>, <Article: NASA uses Python>]>
>>> Article.objects.filter(publications__in=[p1,p2]).distinct()
<QuerySet [<Article: Django lets you build Web apps easily>, <Article: NASA usesPython>]>
 
###
>>> Publication.objects.filter(id=1)
<QuerySet [<Publication: The Python Journal>]> 
>>> Publication.objects.filter(pk=1)
<QuerySet [<Publication: The Python Journal>]>
>>> Publication.objects.filter(article__headline__startswith="NASA")
<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>,
,!<Publication: Science Weekly>, <Publication:
>>> Publication.objects.filter(article__id=1) 
<QuerySet [<Publication: The Python Journal>]> 
>>> Publication.objects.filter(article__pk=1) 
<QuerySet [<Publication: The Python Journal>]> 
>>> Publication.objects.filter(article=1) 
<QuerySet [<Publication: The Python Journal>]> 
>>> Publication.objects.filter(article=a1) 
<QuerySet [<Publication: The Python Journal>]>
>>> Publication.objects.filter(article__in=[1,2]).distinct()
<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>, <Publication: The Python Journal>]>
>>> Publication.objects.filter(article__in=[a1,a2]).distinct()
<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>, <Publication: The Python Journal>]>
 
###
>>> Article.objects.exclude(publications=p2)
<QuerySet [<Article: Django lets you build Web apps easily>]>
 
###
>>> p1.delete()
>>> Publication.objects.all()
<QuerySet [<Publication: Highlights for Children>, <Publication: Science News>, <Publication: Science Weekly>]> 
>>> a1 = Article.objects.get(pk=1) 
>>> a1.publications.all() 
<QuerySet []>
 
###
>>> a2.delete()
>>> Article.objects.all()
<QuerySet [<Article: Django lets you build Web apps easily>]> 
>>> p2.article_set.all()
<QuerySet []>
 
###
>>> a4 = Article(headline='NASA finds intelligent life on Earth') 
>>> a4.save()
>>> p2.article_set.add(a4)
>>> p2.article_set.all()
<QuerySet [<Article: NASA finds intelligent life on Earth>]>
>>> a4.publications.all()
<QuerySet [<Publication: Science News>]>
 
###
>>> new_article = p2.article_set.create(headline='Oxygen-free diet works wonders') 
>>> p2.article_set.all()
<QuerySet [<Article: NASA finds intelligent life on Earth>, <Article: Oxygen-free diet works wonders>]>
>>> a5 = p2.article_set.all()[1]
>>> a5.publications.all()
<QuerySet [<Publication: Science News>]>
 
###
>>> a4.publications.remove(p2)
>>> p2.article_set.all()
<QuerySet [<Article: Oxygen-free diet works wonders>]> 
>>> a4.publications.all()
<QuerySet []>
 
###
>>> p2.article_set.remove(a5) 
>>> p2.article_set.all() 
<QuerySet []>
>>> a5.publications.all() 
<QuerySet []>
 
###
>>> a4.publications.all()
<QuerySet [<Publication: Science News>]> 
>>> a4.publications.set([p3])
>>> a4.publications.all()
<QuerySet [<Publication: Science Weekly>]>
 
###
>>> p2.article_set.clear() 
>>> p2.article_set.all() 
<QuerySet []>
 
###
>>> p2.article_set.add(a4, a5)
>>> p2.article_set.all()
<QuerySet [<Article: NASA finds intelligent life on Earth>, <Article: Oxygen-free diet works wonders>]>
>>> a4.publications.all()
<QuerySet [<Publication: Science News>, <Publication: Science Weekly>]> 
>>> a4.publications.clear()
>>> a4.publications.all()
<QuerySet []>
>>> p2.article_set.all()
<QuerySet [<Article: Oxygen-free diet works wonders>]>
 
###
>>> p1 = Publication(title='The Python Journal') 
>>> p1.save()
>>> a2 = Article(headline='NASA uses Python')
>>> a2.save()
>>> a2.publications.add(p1, p2, p3)
 
###
>>> Publication.objects.filter(title__startswith='Science').delete()
>>> Publication.objects.all()
<QuerySet [<Publication: Highlights for Children>, <Publication: The Python Journal>]> 
>>> Article.objects.all()
<QuerySet [<Article: Django lets you build Web apps easily>, 
<Article: NASA findsintelligent life on Earth>, <Article: NASA uses Python>, 
<Article: Oxygen-free dietworks wonders>]>
>>> a2.publications.all()
<QuerySet [<Publication: The Python Journal>]>
 
###
>>> q = Article.objects.filter(headline__startswith='Django') 
>>> print(q)
<QuerySet [<Article: Django lets you build Web apps easily>]> 
>>> q.delete()
 
###
>>> print(q)
<QuerySet []>
>>> p1.article_set.all()
<QuerySet [<Article: NASA uses Python>]>

from django.db import models
 
class Person(models.Model):
    name = models.CharField(max_length=128) 
    def __str__(self):
        return self.name
 
class Group(models.Model):
    name = models.CharField(max_length=128)
    members = models.ManyToManyField(Person, through='Membership')
    def __str__(self): 
        return self.name
 
class Membership(models.Model):
    person = models.ForeignKey(Person, on_delete=models.CASCADE) 
    group = models.ForeignKey(Group, on_delete=models.CASCADE) 
    date_joined = models.DateField()
    invite_reason = models.CharField(max_length=64)

###
>>> ringo = Person.objects.create(name="Ringo Starr") 
>>> paul = Person.objects.create(name="Paul McCartney") 
>>> beatles = Group.objects.create(name="The Beatles") 
>>> m1 = Membership(person=ringo, group=beatles,
...     date_joined=date(1962, 8, 16),
...     invite_reason="Needed a new drummer.") 
>>> m1.save()
>>> beatles.members.all()
<QuerySet [<Person: Ringo Starr>]>
>>> ringo.group_set.all()
<QuerySet [<Group: The Beatles>]>
>>> m2 = Membership.objects.create(person=paul, group=beatles,
...     date_joined=date(1960, 8, 1),
...     invite_reason="Wanted to form a band.")
>>> beatles.members.all()
<QuerySet [<Person: Ringo Starr>, <Person: Paul McCartney>]>
 
###
>>> # The following statements will not work
>>> beatles.members.add(john)
>>> beatles.members.create(name="George Harrison") 
>>> beatles.members.set([john, paul, ringo, george])
 
###
>>> Membership.objects.create(person=ringo, group=beatles,
...     date_joined=date(1968, 9, 4),
...     invite_reason="You've been gone for a month and we miss you.")
>>> beatles.members.all()
<QuerySet [<Person: Ringo Starr>, <Person: Paul McCartney>, <Person: Ringo Starr>]> 
>>> # This will not work because it cannot tell which membership to remove
>>> beatles.members.remove(ringo)
 
###
>>> # Beatles have broken up
>>> beatles.members.clear()
>>> # Note that this deletes the intermediate model instances >>> Membership.objects.all()
<QuerySet []>
 
###
# Find all the groups with a member whose name starts with 'Paul'
>>> Group.objects.filter(members__name__startswith='Paul') 
<QuerySet [<Group: The Beatles>]>
 
###
# Find all the members of the Beatles that joined after 1 Jan 1961
>>> Person.objects.filter(
...     group__name='The Beatles'
...     membership__date_joined__gt=date(1961,1,1)) 
<QuerySet [<Person: Ringo Starr]>
 
###
>>> ringos_membership = Membership.objects.get(group=beatles, person=ringo) 
>>> ringos_membership.date_joined
datetime.date(1962, 8, 16)
>>> ringos_membership.invite_reason
'Needed a new drummer.'
 
###
>>> ringos_membership = ringo.membership_set.get(group=beatles) 
>>> ringos_membership.date_joined
datetime.date(1962, 8, 16)
>>> ringos_membership.invite_reason
'Needed a new drummer.'
 

8. Models across files

1 2 3 4 5 6 7 8 9 10 11

from django.db import models from geography.models import ZipCode   class Restaurant(models.Model):     # ...     zip_code = models.ForeignKey(          ZipCode,         on_delete=models.SET_NULL,          blank=True,         null=True,     ) Colored by Color Scripter

cs

9. Field 명 제약

class Example(models.Model):
pass = models.IntegerField() 
# 'pass' is a reserved word!
 
class Example(models.Model):
foo__bar = models.IntegerField() 
# 'foo__bar' has two underscores!

 - 예약어

 - 2번의 언더스코어

10. Meta options

from django.db import models 
 
class Ox(models.Model):
    horn_length = models.IntegerField()
    class Meta:
        ordering = ["horn_length"] 
        verbose_name_plural = "oxen"

 - ordering : 정렬 컬럼 설정

 - verbose_name : 요약된 컬럼의 이름

 - verbose_name_plural : verbose_name의 복수형

 - db_table : 테이블명

 - base_manager_name : manager 지정

 - abstract : 추상모델 (부모클래스는 DB에 테이블이 생성되지 않는다.)

###
from django.db import models
 
class CommonInfo(models.Model):
    name = models.CharField(max_length=100) 
    age = models.PositiveIntegerField()
 
    class Meta: 
        abstract = True
 
    class Student(CommonInfo):
        home_group = models.CharField(max_length=5)
 
###
from django.db import models
 
class CommonInfo(models.Model): 
    # ...
    class Meta: abstract = True
        ordering = ['name']
 
class Student(CommonInfo): 
    # ...
    class Meta(CommonInfo.Meta): 
        db_table = 'student_info'

11. Models methods

from django.db import models
 
class Person(models.Model):
    first_name = models.CharField(max_length=50) 
    last_name = models.CharField(max_length=50) 
    birth_date = models.DateField()
 
    def baby_boomer_status(self):
        "Returns the person's baby-boomer status." 
        import datetime
        if self.birth_date < datetime.date(1945, 8, 1):
            return "Pre-boomer"
        elif self.birth_date < datetime.date(1965, 1, 1):
            return "Baby boomer" 
        else:
            return "Post-boomer"
 
    @property
    def full_name(self):
        "Returns the person's full name."
        return '%s %s' % (self.first_name, self.last_name)

- property 데코레이터를 사용하여 얻고 싶은 값을 지정하는 getter

 - get_absolte_url() : 개별 데이터 접근 url (PK 접근)

###
def get_absolute_url(self):
    return "/people/%i/" % self.id
 
###
def get_absolute_url(self):
    from django.urls import reverse
    return reverse('people.views.details', args=[str(self.id)])
 
###
<!-- BAD template code. Avoid! -->
<a href="/people/{{ object.id }}/">{{ object.name }}</a>
 
###
<!-- Much better! -->
<a href="{{ object.get_absolute_url }}">{{ object.name }}</a>

 - save() : 데이터 저장시 추가 작업을 할 경우

###
from django.db import models
 
class Blog(models.Model):
    name = models.CharField(max_length=100) 
    tagline = models.TextField()
    def save(self, *args, **kwargs): 
        do_something()
        super().save(*args, **kwargs) # Call the "real" save() method. do_something_else()
 
###
from django.db import models
 
class Blog(models.Model):
    name = models.CharField(max_length=100) 
    tagline = models.TextField()
 
    def save(self, *args, **kwargs):
        if self.name == "Yoko Ono's blog":
            return # Yoko shall never have her own blog! 
        else:
            super().save(*args, **kwargs) # Call the "real" save() method.

12. Model 상속

 - Multi-table inheritance (부모는 자식을 포함한다.)

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### from django.db import models   class Place(models.Model):     name = models.CharField(max_length=50)      address = models.CharField(max_length=80)   class Restaurant(Place):     serves_hot_dogs = models.BooleanField(default=False)      serves_pizza = models.BooleanField(default=False)   ### >>> Place.objects.filter(name="Bob's Cafe") >>> Restaurant.objects.filter(name="Bob's Cafe")   ### >>> p = Place.objects.get(id=12) # If p is a Restaurant object, this will give the child class: >>> p.restaurant  <Restaurant: ...>   ### place_ptr = models.OneToOneField(      Place,      on_delete=models.CASCADE,      parent_link=True, ) Colored by Color Scripter

 - Meta and multi-table inheritance

(자식은 부모의 Meta 클래스를 상속받지 않지만, ordering, get_latest_by 옵션이 설정되지 않았을 경우에만 해당 설정값을 상속받는다.)

1 2 3 4 5

class ChildModel(ParentModel):     # ...     class Meta:         # Remove parent's ordering effect          ordering = []

cs

 - Inheritance and reverse relations

###
class Supplier(Place):
    customers = models.ManyToManyField(Place)
 
###
Reverse query name for 'Supplier.customers' clashes with reverse query 
name for 'Supplier.place_ptr'.
 
HINT: Add or change a related_name argument to the definition for 
'Supplier.customers' or 'Supplier.place_ptr'.
 
###
models. ManyToManyField(Place, related_name='provider')