如何组合我的Django模型，这样我就不会重复自己了

Question

我意识到我现在使用的3个模型有大量的共享字段。我想知道压缩这些模型的最佳方式是什么；最好的"；这样做的方法是。

型号.py

class Car(models.Model):
created = models.DateTimeField(auto_now_add=True)
make = models.CharField(max_length=100)
model = models.CharField(max_length=100)
year = models.IntegerField(default=2021, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])
seats = models.PositiveSmallIntegerField()
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

class Truck(models.Model):
created = models.DateTimeField(auto_now_add=True)
make = models.CharField(max_length=100)
model = models.CharField(max_length=100)
year = models.IntegerField(default=datetime.now().year, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])
seats = models.PositiveSmallIntegerField()
bed_length = models.CharField(max_length=100)
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

class Boat(models.Model):
created = models.DateTimeField(auto_now_add=True)
make = models.CharField(max_length=100)
model = models.CharField(max_length=100)
year = models.PositiveSmallIntegerField(default=datetime.now().year, validators=[MaxValueValidator(datetime.now().year)])
length = models.CharField(max_length=100)
width = models.CharField(max_length=100)
HIN = models.CharField(max_length=14, validators=[MinLengthValidator(12)], blank=True)
current_hours = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

Answer 1

我可以注意到有些字段是相似的，但并不相同，例如year并非所有字段都相同。因此，我向你提出以下建议。

class TimeStampedModel(models.Model):
created = models.DateTimeField(auto_now_add=True)
modified = models.DateTimeField(auto_now=True)
class Meta:
abstract = True

class Vehicule(TimeStampedModel):
make = models.CharField(max_length=100)
model = models.CharField(max_length=100)
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)
class Meta:
abstract = True

class WheeledVehicle(Vehicule):
seats = models.PositiveSmallIntegerField()
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
class Meta:
abstract = True

class Car(WheeledVehicle):
year = models.IntegerField(default=2021, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])


class Truck(WheeledVehicle):
year = models.IntegerField(default=datetime.now().year, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])
bed_length = models.CharField(max_length=100)

class Boat(Vehicule):
year = models.PositiveSmallIntegerField(default=datetime.now().year, validators=[MaxValueValidator(datetime.now().year)])
length = models.CharField(max_length=100)
width = models.CharField(max_length=100)
HIN = models.CharField(max_length=14, validators=[MinLengthValidator(12)], blank=True)
current_hours = models.PositiveSmallIntegerField()

如果您想更进一步，我建议您添加要审核的created_by和modified_by字段。

class TimeStampedModel(models.Model):
created = models.DateTimeField(auto_now_add=True)
modified = models.DateTimeField(auto_now=True)
class Meta:
abstract = True
class TimeStampedAuthModel(TimeStampedModel):
created_by = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, on_delete=models.SET_NULL,
related_name="%(app_label)s_%(class)s_created_by")
modified_by = models.ForeignKey(settings.AUTH_USER_MODEL, null=True, on_delete=models.SET_NULL,
related_name="%(app_label)s_%(class)s_modified_by")
class Meta:
abstract = True

class Vehicule(TimeStampedAuthModel):
make = models.CharField(max_length=100)
model = models.CharField(max_length=100)
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)
class Meta:
abstract = True

class WheeledVehicle(Vehicule):
seats = models.PositiveSmallIntegerField()
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
class Meta:
abstract = True

class Car(WheeledVehicle):
year = models.IntegerField(default=2021, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])


class Truck(WheeledVehicle):
year = models.IntegerField(default=datetime.now().year, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])
bed_length = models.CharField(max_length=100)

class Boat(Vehicule):
year = models.PositiveSmallIntegerField(default=datetime.now().year, validators=[MaxValueValidator(datetime.now().year)])
length = models.CharField(max_length=100)
width = models.CharField(max_length=100)
HIN = models.CharField(max_length=14, validators=[MinLengthValidator(12)], blank=True)
current_hours = models.PositiveSmallIntegerField()

Answer 2

您可以使用模型继承或模型混合

具有抽象基础模型的模型继承：

class AbstractVehicle(models.Model):
created = models.DateTimeField(auto_now_add=True)
make = models.CharField(max_length=100)
model = models.CharField(max_length=100)
year = models.IntegerField(default=2021, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])

class Meta:
abstract = True
class Car(AbstractVehicle):
seats = models.PositiveSmallIntegerField()    
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

class Truck(AbstractVehicle):
seats = models.PositiveSmallIntegerField()
bed_length = models.CharField(max_length=100)
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

class Boat(AbstractVehicle):
length = models.CharField(max_length=100)
width = models.CharField(max_length=100)
HIN = models.CharField(max_length=14, validators=[MinLengthValidator(12)], blank=True)
current_hours = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

模型混合：

class VehicleMixin(object):
created = models.DateTimeField(auto_now_add=True)
make = models.CharField(max_length=100)
model = models.CharField(max_length=100)
year = models.IntegerField(default=2021, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])
class Car(VehicleMixin, models.Model):
seats = models.PositiveSmallIntegerField()    
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

class Truck(VehicleMixin, models.Model):
seats = models.PositiveSmallIntegerField()
bed_length = models.CharField(max_length=100)
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

class Boat(VehicleMixin, models.Model):
length = models.CharField(max_length=100)
width = models.CharField(max_length=100)
HIN = models.CharField(max_length=14, validators=[MinLengthValidator(12)], blank=True)
current_hours = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)

这两种解决方案都将为您留下与代码相同的表。这些也只是简单的例子。你也许可以进一步改进它们。例如，您可以添加更多包含其他字段的mixin或抽象基类。

Answer 3

您可以通过在车辆模型中创建Vehicle和VehicleType来组合模型-您保留所有常见的车辆字段，在VehicleType中保留汽车、卡车、船只等，并使用外键引用Vehicle模型。

class VehicleType(models.Model):
name = models.CharField(max_length=100, unique=True)
created = models.DateTimeField(auto_now_add=True)
class Vehicle(models.Model):
vehicle_type = models.Foreinkey(VehicleType, on_delete=model.CASCADE)
created = models.DateTimeField(auto_now_add=True)
make = models.CharField(max_length=100)
model = models.CharField(max_length=100)
year = models.IntegerField(default=datetime.now().year, validators=[MinValueValidator(1886), MaxValueValidator(datetime.now().year)])
seats = models.PositiveSmallIntegerField()
bed_length = models.CharField(max_length=100)
color = models.CharField(max_length=100)
VIN = models.CharField(max_length=17, validators=[MinLengthValidator(11)])
current_mileage = models.PositiveSmallIntegerField()
service_interval = models.CharField(max_length=50)
next_service = models.CharField(max_length=50)