Changes in 53e31d8: Created Django Model Field Tricks (markdown)

				Django/Django Model Field Tricks.md
			
          @@ -0,0 +1,183 @@

          +# 10 Django Model Field Tricks You Probably Didn’t Know About | by Haider Alaamery | Dec, 2024 | Medium

          +

          +https://halaamery.medium.com/10-django-model-field-tricks-you-probably-didnt-know-about-fc97f3148bc0

          +

          +![Haider Alaamery](https://miro.medium.com/v2/resize:fill:88:88/1*JF-tc5tO_oML1KH7Q5_oAQ.jpeg)

          +[Haider Alaamery](https://halaamery.medium.com/)

          +

          +1\. Customizing Field Validation with `clean()`

          +-----------------------------------------------

          +

          +Did you know you can add custom validation logic to specific fields using the `clean()` method?

          +

          +```

          +from django.db import models

          +from django.core.exceptions import ValidationError

          +class Product(models.Model):

          +    name = models.CharField(max_length=100)

          +    price = models.DecimalField(max_digits=10, decimal_places=2)

          +def clean(self):

          +    if self.price <= 0:

          +    raise ValidationError("Price must be greater than zero.")

          +```

          +

          +

          +> Use `clean()` in your save logic or forms to ensure that invalid data never sneaks into your database.

          +

          +2\. Conditional Default Values

          +------------------------------

          +

          +Sometimes, you need default values to change dynamically based on some condition.

          +

          +```

          +from django.utils.timezone import now

          +class Event(models.Model):

          +    name = models.CharField(max_length=100)

          +    start_date = models.DateTimeField(default=now)

          +    end_date = models.DateTimeField(default=lambda: now() + timedelta(days=7))

          +```

          +

          +

          +> This is great for timestamps or automatically generating default future dates.

          +

          +3\. **Unique Constraints for Multi-Field Uniqueness**

          +-----------------------------------------------------

          +

          +Replace the deprecated unique\_together with UniqueConstraint for better control.

          +

          +```

          +from django.db import models

          +class Membership(models.Model):

          +    user = models.ForeignKey('auth.User', on_delete=models.CASCADE)

          +    group = models.ForeignKey('Group', on_delete=models.CASCADE)

          +    class Meta:

          +        constraints = [

          +            models.UniqueConstraint(fields=['user', 'group'], name='unique_membership')

          +        ]

          +```

          +

          +

          +> This ensures no user can be added to the same group twice.

          +

          +4\. **Using** `**choices**` **with Enums**

          +------------------------------------------

          +

          +Django’s `choices` make fields cleaner, especially with Enums.

          +

          +```

          +from django.db import models

          +class Status(models.TextChoices):

          +    PENDING = 'P', 'Pending'

          +    APPROVED = 'A', 'Approved'

          +    REJECTED = 'R', 'Rejected'

          +class Request(models.Model):

          +    status = models.CharField(max_length=1, choices=Status.choices, default=Status.PENDING)

          +```

          +

          +

          +> Access your choices like `Status.PENDING` instead of raw strings.

          +

          +5\. `through` for Many-to-Many Customization

          +--------------------------------------------

          +

          +Need extra data in your Many-to-Many relationships? Use `through`.

          +

          +```

          +class Author(models.Model):

          +    name = models.CharField(max_length=100)

          +class Book(models.Model):

          +    title = models.CharField(max_length=100)

          +    authors = models.ManyToManyField(Author, through='Authorship')

          +class Authorship(models.Model):

          +    author = models.ForeignKey(Author, on_delete=models.CASCADE)

          +    book = models.ForeignKey(Book, on_delete=models.CASCADE)

          +    role = models.CharField(max_length=50)  # e.g., "Co-Author", "Editor"

          +```

          +

          +

          +> This allows you to track additional details about the relationship.

          +

          +6\. Field-Level Permissions with `editable=False`

          +-------------------------------------------------

          +

          +Prevent direct editing in admin while still allowing updates programmatically.

          +

          +```

          +class Order(models.Model):

          +    total_price = models.DecimalField(max_digits=10, decimal_places=2, editable=False)

          +```

          +

          +

          +> You can still update `total_price` in your code but not in the admin.

          +

          +7\. Custom File Upload Paths

          +----------------------------

          +

          +Organize uploaded files dynamically with `upload_to`.

          +

          +```

          +def upload_to(instance, filename):

          +    return f"uploads/{instance.user.id}/{filename}"

          +class Profile(models.Model):

          +    user = models.OneToOneField('auth.User', on_delete=models.CASCADE)

          +    avatar = models.ImageField(upload_to=upload_to)

          +```

          +

          +

          +> Uploaded files are neatly stored based on the user’s ID.

          +

          +8\. Using `Property` Fields in Models

          +-------------------------------------

          +

          +Django models can include computed properties.

          +

          +```

          +class Employee(models.Model):

          +    first_name = models.CharField(max_length=50)

          +    last_name = models.CharField(max_length=50)

          +    @property

          +    def full_name(self):

          +        return f"{self.first_name} {self.last_name}"

          +```

          +

          +

          +> Access it like a field: `employee.full_name`.

          +

          +9\. Auto-Setting Fields with `save()`

          +-------------------------------------

          +

          +Customize field behavior by overriding `save()`.

          +

          +```

          +class Article(models.Model):

          +    title = models.CharField(max_length=100)

          +    slug = models.SlugField(unique=True, blank=True)

          +    def save(self, *args, **kwargs):

          +        if not self.slug:

          +            self.slug = self.title.lower().replace(' ', '-')

          +        super().save(*args, **kwargs)

          +```

          +

          +

          +> Automatically generate slugs from titles if not provided.

          +

          +10\. Soft Deletes with `is_archived`

          +------------------------------------

          +

          +Instead of deleting records, archive them.

          +

          +```

          +class BaseModel(models.Model):

          +    is_archived = models.BooleanField(default=False)

          +    def delete(self, *args, **kwargs):

          +        self.is_archived = True

          +        self.save()

          +    class Meta:

          +        abstract = True

          +```

          +

          +

          +> Your data stays safe while appearing “deleted” to the user.

          +

          +**Conclusion:**  

          +Django’s model system is powerful, and these tricks can help you write cleaner, more efficient code. Which of these tricks are you already using? What’s your favorite?

          \ No newline at end of file

...	...	@@ -0,0 +1,183 @@
	1	+# 10 Django Model Field Tricks You Probably Didn’t Know About \| by Haider Alaamery \| Dec, 2024 \| Medium
	2	+
	3	+https://halaamery.medium.com/10-django-model-field-tricks-you-probably-didnt-know-about-fc97f3148bc0
	4	+
	5	+![Haider Alaamery](https://miro.medium.com/v2/resize:fill:88:88/1*JF-tc5tO_oML1KH7Q5_oAQ.jpeg)
	6	+[Haider Alaamery](https://halaamery.medium.com/)
	7	+
	8	+1\. Customizing Field Validation with `clean()`
	9	+-----------------------------------------------
	10	+
	11	+Did you know you can add custom validation logic to specific fields using the `clean()` method?
	12	+
	13	+```
	14	+from django.db import models
	15	+from django.core.exceptions import ValidationError
	16	+class Product(models.Model):
	17	+ name = models.CharField(max_length=100)
	18	+ price = models.DecimalField(max_digits=10, decimal_places=2)
	19	+def clean(self):
	20	+ if self.price <= 0:
	21	+ raise ValidationError("Price must be greater than zero.")
	22	+```
	23	+
	24	+
	25	+> Use `clean()` in your save logic or forms to ensure that invalid data never sneaks into your database.
	26	+
	27	+2\. Conditional Default Values
	28	+------------------------------
	29	+
	30	+Sometimes, you need default values to change dynamically based on some condition.
	31	+
	32	+```
	33	+from django.utils.timezone import now
	34	+class Event(models.Model):
	35	+ name = models.CharField(max_length=100)
	36	+ start_date = models.DateTimeField(default=now)
	37	+ end_date = models.DateTimeField(default=lambda: now() + timedelta(days=7))
	38	+```
	39	+
	40	+
	41	+> This is great for timestamps or automatically generating default future dates.
	42	+
	43	+3\. Unique Constraints for Multi-Field Uniqueness
	44	+-----------------------------------------------------
	45	+
	46	+Replace the deprecated unique\_together with UniqueConstraint for better control.
	47	+
	48	+```
	49	+from django.db import models
	50	+class Membership(models.Model):
	51	+ user = models.ForeignKey('auth.User', on_delete=models.CASCADE)
	52	+ group = models.ForeignKey('Group', on_delete=models.CASCADE)
	53	+ class Meta:
	54	+ constraints = [
	55	+ models.UniqueConstraint(fields=['user', 'group'], name='unique_membership')
	56	+ ]
	57	+```
	58	+
	59	+
	60	+> This ensures no user can be added to the same group twice.
	61	+
	62	+4\. Using `choices` with Enums
	63	+------------------------------------------
	64	+
	65	+Django’s `choices` make fields cleaner, especially with Enums.
	66	+
	67	+```
	68	+from django.db import models
	69	+class Status(models.TextChoices):
	70	+ PENDING = 'P', 'Pending'
	71	+ APPROVED = 'A', 'Approved'
	72	+ REJECTED = 'R', 'Rejected'
	73	+class Request(models.Model):
	74	+ status = models.CharField(max_length=1, choices=Status.choices, default=Status.PENDING)
	75	+```
	76	+
	77	+
	78	+> Access your choices like `Status.PENDING` instead of raw strings.
	79	+
	80	+5\. `through` for Many-to-Many Customization
	81	+--------------------------------------------
	82	+
	83	+Need extra data in your Many-to-Many relationships? Use `through`.
	84	+
	85	+```
	86	+class Author(models.Model):
	87	+ name = models.CharField(max_length=100)
	88	+class Book(models.Model):
	89	+ title = models.CharField(max_length=100)
	90	+ authors = models.ManyToManyField(Author, through='Authorship')
	91	+class Authorship(models.Model):
	92	+ author = models.ForeignKey(Author, on_delete=models.CASCADE)
	93	+ book = models.ForeignKey(Book, on_delete=models.CASCADE)
	94	+ role = models.CharField(max_length=50) # e.g., "Co-Author", "Editor"
	95	+```
	96	+
	97	+
	98	+> This allows you to track additional details about the relationship.
	99	+
	100	+6\. Field-Level Permissions with `editable=False`
	101	+-------------------------------------------------
	102	+
	103	+Prevent direct editing in admin while still allowing updates programmatically.
	104	+
	105	+```
	106	+class Order(models.Model):
	107	+ total_price = models.DecimalField(max_digits=10, decimal_places=2, editable=False)
	108	+```
	109	+
	110	+
	111	+> You can still update `total_price` in your code but not in the admin.
	112	+
	113	+7\. Custom File Upload Paths
	114	+----------------------------
	115	+
	116	+Organize uploaded files dynamically with `upload_to`.
	117	+
	118	+```
	119	+def upload_to(instance, filename):
	120	+ return f"uploads/{instance.user.id}/{filename}"
	121	+class Profile(models.Model):
	122	+ user = models.OneToOneField('auth.User', on_delete=models.CASCADE)
	123	+ avatar = models.ImageField(upload_to=upload_to)
	124	+```
	125	+
	126	+
	127	+> Uploaded files are neatly stored based on the user’s ID.
	128	+
	129	+8\. Using `Property` Fields in Models
	130	+-------------------------------------
	131	+
	132	+Django models can include computed properties.
	133	+
	134	+```
	135	+class Employee(models.Model):
	136	+ first_name = models.CharField(max_length=50)
	137	+ last_name = models.CharField(max_length=50)
	138	+ @property
	139	+ def full_name(self):
	140	+ return f"{self.first_name} {self.last_name}"
	141	+```
	142	+
	143	+
	144	+> Access it like a field: `employee.full_name`.
	145	+
	146	+9\. Auto-Setting Fields with `save()`
	147	+-------------------------------------
	148	+
	149	+Customize field behavior by overriding `save()`.
	150	+
	151	+```
	152	+class Article(models.Model):
	153	+ title = models.CharField(max_length=100)
	154	+ slug = models.SlugField(unique=True, blank=True)
	155	+ def save(self, args, *kwargs):
	156	+ if not self.slug:
	157	+ self.slug = self.title.lower().replace(' ', '-')
	158	+ super().save(args, *kwargs)
	159	+```
	160	+
	161	+
	162	+> Automatically generate slugs from titles if not provided.
	163	+
	164	+10\. Soft Deletes with `is_archived`
	165	+------------------------------------
	166	+
	167	+Instead of deleting records, archive them.
	168	+
	169	+```
	170	+class BaseModel(models.Model):
	171	+ is_archived = models.BooleanField(default=False)
	172	+ def delete(self, args, *kwargs):
	173	+ self.is_archived = True
	174	+ self.save()
	175	+ class Meta:
	176	+ abstract = True
	177	+```
	178	+
	179	+
	180	+> Your data stays safe while appearing “deleted” to the user.
	181	+
	182	+Conclusion:
	183	+Django’s model system is powerful, and these tricks can help you write cleaner, more efficient code. Which of these tricks are you already using? What’s your favorite?
...	...	\ No newline at end of file