Test cases for ORM queries mentioned in book and some typo fix

.github/workflows/django.yml

@@ -0,0 +1,30 @@
+name: Django CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      max-parallel: 4
+      matrix:
+        python-version: [3.6, 3.7, 3.8]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install Dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r heroes_and_monsters/requirements.txt
+    - name: Run Tests
+      run: |
+        cd heroes_and_monsters && python manage.py test

docs/notequal_query.rst

@@ -22,11 +22,7 @@ Our SQL query for the above condition will look something like ::
 
 .. image:: sqluser_notquery.png
 
-Method 1 using exclude
-
-.. code-block
-
-
+Method 1 using exclude ::
 
     >>> queryset = User.objects.exclude(id__lt=5)
     >>> queryset

docs/one_to_many.rst

@@ -30,7 +30,7 @@ To define a many-to-one relationship, use `ForeignKey`.::
 If you try to assign an object before saving it you will encounter a ValueError ::
 
     >>> u3 = User(username='someuser', first_name='Some', last_name='User', email='[email protected]')
-    >>> Article.objects.create(headline="This is a test", pub_date=date(2018, 3, 7), reporter=u1)
+    >>> Article.objects.create(headline="This is a test", pub_date=date(2018, 3, 7), reporter=u3)
     Traceback (most recent call last):
     ...
     ValueError: save() prohibited to prevent data loss due to unsaved related object 'reporter'.

heroes_and_monsters/.env

@@ -1,2 +1,2 @@
-DATABASE_URL=postgres://umsra:umsra@localhost:5432/umsra
+DATABASE_URL=sqlite:///db.sqlite3
 export DATABASE_URL

heroes_and_monsters/entities/models.py

@@ -17,23 +17,23 @@ class Meta:
     @classmethod
     def truncate(cls):
         with connection.cursor() as cursor:
-            cursor.execute('TRUNCATE TABLE "{0}" CASCADE'.format(cls._meta.db_table))
-
+            cursor.execute('DELETE FROM "{0}"'.format(cls._meta.db_table))
 
     def __str__(self):
         return self.name
 
 
 from django.contrib.contenttypes.fields import GenericForeignKey, GenericRelation
 from django.contrib.contenttypes.models import ContentType
+
 # ...
 
+
 class FlexCategory(models.Model):
     name = models.SlugField()
     content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
     object_id = models.PositiveIntegerField()
-    content_object = GenericForeignKey('content_type', 'object_id')
-
+    content_object = GenericForeignKey("content_type", "object_id")
 
 
 class Origin(models.Model):
@@ -54,26 +54,24 @@ class Entity(models.Model):
     GENDER_OTHERS = "Others/Unknown"
 
     name = models.CharField(max_length=100)
-    alternative_name = models.CharField(
-        max_length=100, null=True, blank=True
-    )
-
+    alternative_name = models.CharField(max_length=100, null=True, blank=True)
 
     category = models.ForeignKey(Category, on_delete=models.CASCADE)
-    flex_category = GenericRelation(FlexCategory, related_query_name='flex_category')
+    flex_category = GenericRelation(FlexCategory, related_query_name="flex_category")
     origin = models.ForeignKey(Origin, on_delete=models.CASCADE)
     gender = models.CharField(
         max_length=100,
         choices=(
             (GENDER_MALE, GENDER_MALE),
             (GENDER_FEMALE, GENDER_FEMALE),
             (GENDER_OTHERS, GENDER_OTHERS),
-        )
+        ),
     )
     description = models.TextField()
 
-    added_by = models.ForeignKey(settings.AUTH_USER_MODEL,
-        null=True, blank=True, on_delete=models.SET_NULL)
+    added_by = models.ForeignKey(
+        settings.AUTH_USER_MODEL, null=True, blank=True, on_delete=models.SET_NULL
+    )
     added_on = models.DateField(auto_now=True)
 
     def __str__(self):
@@ -84,7 +82,6 @@ class Meta:
 
 
 class Hero(Entity):
-
     class Meta:
         verbose_name_plural = "Heroes"
 
@@ -95,19 +92,21 @@ class Meta:
     is_immortal = models.BooleanField(default=True)
 
     benevolence_factor = models.PositiveSmallIntegerField(
-        help_text="How benevolent this hero is?",
-        default=50
+        help_text="How benevolent this hero is?", default=50
     )
     arbitrariness_factor = models.PositiveSmallIntegerField(
-        help_text="How arbitrary this hero is?",
-        default=50
+        help_text="How arbitrary this hero is?", default=50
     )
 
     headshot = models.ImageField(null=True, blank=True, upload_to="hero_headshots/")
 
     # relationships
     father = models.ForeignKey(
-        "self", related_name="children", null=True, blank=True, on_delete=models.SET_NULL
+        "self",
+        related_name="children",
+        null=True,
+        blank=True,
+        on_delete=models.SET_NULL,
     )
     mother = models.ForeignKey(
         "self", related_name="+", null=True, blank=True, on_delete=models.SET_NULL
@@ -116,12 +115,19 @@ class Meta:
         "self", related_name="+", null=True, blank=True, on_delete=models.SET_NULL
     )
 
+    def save(self, *args, **kwargs):
+        if not self.pk:
+            Category.objects.filter(pk=self.category_id).update(
+                hero_count=F("hero_count") + 1
+            )
+        super().save(*args, **kwargs)
+
 
 class HeroProxy(Hero):
-
     class Meta:
         proxy = True
 
+
 class Villain(Entity):
     is_immortal = models.BooleanField(default=False)
 
@@ -134,9 +140,12 @@ class Villain(Entity):
     is_unique = models.BooleanField(default=True)
     count = models.PositiveSmallIntegerField(default=1)
 
-    # def save(self, *args, **kwargs):
-    #     super().save(*args, **kwargs)
-    #     Category.objects.filter(pk=self.category_pk).update(villain_count=F(villain_count)+1)
+    def save(self, *args, **kwargs):
+        if not self.pk:
+            Category.objects.filter(pk=self.category_id).update(
+                villain_count=F("villain_count") + 1
+            )
+        super().save(*args, **kwargs)
 
 
 class HeroAcquaintance(models.Model):
@@ -156,18 +165,17 @@ class Meta:
         db_table = "entities_entity"
 
 
-from django.db.models.signals import pre_save
-from django.dispatch import receiver
-
-@receiver(pre_save, sender=Hero, dispatch_uid="update_hero_count")
-def update_hero_count(sender, **kwargs):
-    hero = kwargs['instance']
-    if hero.pk:
-        Category.objects.filter(pk=hero.category_id).update(hero_count=F('hero_count')+1)
+# from django.db.models.signals import pre_save
+# from django.dispatch import receiver
 
-@receiver(pre_save, sender=Villain, dispatch_uid="update_villain_count")
-def update_villain_count(sender, **kwargs):
-    villain = kwargs['instance']
-    if villain.pk:
-        Category.objects.filter(pk=villain.category_id).update(villain_count=F('villain_count')+1)
+# @receiver(pre_save, sender=Hero, dispatch_uid="update_hero_count")
+# def update_hero_count(sender, **kwargs):
+#     hero = kwargs['instance']
+#     if hero.pk:
+#         Category.objects.filter(pk=hero.category_id).update(hero_count=F('hero_count')+1)
 
+# @receiver(pre_save, sender=Villain, dispatch_uid="update_villain_count")
+# def update_villain_count(sender, **kwargs):
+#     villain = kwargs['instance']
+#     if villain.pk:
+#         Category.objects.filter(pk=villain.category_id).update(villain_count=F('villain_count')+1)