Python django中业务逻辑和数据访问的分离

我正在用Django编写一个项目，我看到80%的代码都在文件

models.py

中。这段代码令人困惑，经过一段时间后，我不再理解真正发生的事情

以下是困扰我的问题：

我发现我的模型级别（应该是 仅负责处理数据库中的数据）也是 发送电子邮件、在API上漫游到其他服务等

此外，我发现在视图中放置业务逻辑是不可接受的，因为 这样就很难控制了。例如，在我的 应用程序创建新应用程序至少有三种方法

用户的实例

，但从技术上讲，它应该统一创建它们

我并不总是注意到方法和 我的模型的属性在发展时变得不确定 副作用

下面是一个简单的例子。起初，

用户

模型是这样的：

class User(db.Models):

    def get_present_name(self):
        return self.name or 'Anonymous'

    def activate(self):
        self.status = 'activated'
        self.save()

随着时间的推移，它变成了这样：

class User(db.Models):

    def get_present_name(self): 
        # property became non-deterministic in terms of database
        # data is taken from another service by api
        return remote_api.request_user_name(self.uid) or 'Anonymous' 

    def activate(self):
        # method now has a side effect (send message to user)
        self.status = 'activated'
        self.save()
        send_mail('Your account is activated!', '…', [self.email])

我想要的是在我的代码中分离实体：

我的数据库实体，持久性级别：我的应用程序保存哪些数据？

我的应用程序的实体，业务逻辑级别：我的应用程序做什么？

---

在Django中实现这种方法的最佳实践是什么？

我通常在视图和模型之间实现一个服务层。这就像您的项目的API一样，可以让您从直升机上很好地了解正在发生的事情。我从我的一位同事那里继承了这种做法，他在Java项目（JSF）中大量使用这种分层技术，例如：

型号.py

class Book:
   author = models.ForeignKey(User)
   title = models.CharField(max_length=125)

   class Meta:
       app_label = "library"

services.py

from library.models import Book

def get_books(limit=None, **filters):
    """ simple service function for retrieving books can be widely extended """
    return Book.objects.filter(**filters)[:limit]  # list[:None] will return the entire list

from library.services import get_books

class BookListView(ListView):
    """ simple view, e.g. implement a _build and _apply filters function """
    queryset = get_books()

def activate_user(user_id):
    user = User.objects.get(pk=user_id)

    # set active flag
    user.active = True
    user.save()

    # mail user
    send_mail(...)

    # etc etc

class ActivateUserForm(forms.Form):

    user_id = IntegerField(widget = UsernameSelectWidget, verbose_name="Select a user to activate")
    # the username select widget is not a standard Django widget, I just made it up

    def clean_user_id(self):
        user_id = self.cleaned_data['user_id']
        if User.objects.get(pk=user_id).active:
            raise ValidationError("This user cannot be activated")
        # you can also check authorizations etc. 
        return user_id

    def execute(self):
        """
        This is not a standard method in the forms API; it is intended to replace the 
        'extract-data-from-form-in-view-and-do-stuff' pattern by a more testable pattern. 
        """
        user_id = self.cleaned_data['user_id']

        user = User.objects.get(pk=user_id)

        # set active flag
        user.active = True
        user.save()

        # mail user
        send_mail(...)

        # etc etc

@register.filter
def friendly_name(user):
    return remote_api.get_cached_name(user.id)

def inactive_users():
    return User.objects.filter(active=False)


def users_called_publysher():
    for user in User.objects.all():
        if remote_api.get_cached_name(user.id) == "publysher":
            yield user 

class InactiveUserManager(models.Manager):
    def get_queryset(self):
        query_set = super(InactiveUserManager, self).get_queryset()
        return query_set.filter(active=False)

class InactiveUser(User):
    """
    >>> for user in InactiveUser.objects.all():
    …        assert user.active is False 
    """

    objects = InactiveUserManager()
    class Meta:
        proxy = True

class InactiveUserDistribution(models.Model):
    country = CharField(max_length=200)
    inactive_user_count = IntegerField(default=0)

class ActivateUserForm(forms.Form):
    # see above
   
    def execute(self):
        # see above
        query_model = InactiveUserDistribution.objects.get_or_create(country=user.country)
        query_model.inactive_user_count -= 1
        query_model.save()

user_activated = Signal(providing_args = ['user'])
user_deactivated = Signal(providing_args = ['user'])

class ActivateUserForm(forms.Form):
    # see above
   
    def execute(self):
        # see above
        user_activated.send_robust(sender=self, user=user)

class InactiveUserDistribution(models.Model):
    # see above

@receiver(user_activated)
def on_user_activated(sender, **kwargs):
        user = kwargs['user']
        query_model = InactiveUserDistribution.objects.get_or_create(country=user.country)
        query_model.inactive_user_count -= 1
        query_model.save()
    

import datetime

from djongo import models
from django.db.models.query import QuerySet
from django.contrib import admin
from django.db import transaction


class MyUser(models.Model):

    present_name = models.TextField(null=False, blank=True)
    status = models.TextField(null=False, blank=True)
    last_active = models.DateTimeField(auto_now=True, editable=False)

    # As mentioned you could put this in a template tag to pull it
    # from cache there. Depending on how it is used, it could be
    # retrieved from within the admin view or from a custom view
    # if that is the only place you will use it.
    #def get_present_name(self):
    #    # property became non-deterministic in terms of database
    #    # data is taken from another service by api
    #    return remote_api.request_user_name(self.uid) or 'Anonymous'

    # Moved to admin as an action
    # def activate(self):
    #     # method now has a side effect (send message to user)
    #     self.status = 'activated'
    #     self.save()
    #     # send email via email service
    #     #send_mail('Your account is activated!', '…', [self.email])

    class Meta:
        ordering = ['-id']  # Needed for DRF pagination

    def __unicode__(self):
        return '{}'.format(self.pk)


class MyUserRegistrationQuerySet(QuerySet):

    def for_inactive_users(self):
        new_date = datetime.datetime.now() - datetime.timedelta(days=3*365)  # 3 Years ago
        return self.filter(last_active__lte=new_date.year)

    def by_user_id(self, user_ids):
        return self.filter(id__in=user_ids)


class MyUserRegistrationManager(models.Manager):

    def get_query_set(self):
        return MyUserRegistrationQuerySet(self.model, using=self._db)

    def with_no_activity(self):
        return self.get_query_set().for_inactive_users()

# Then in model admin

class MyUserRegistrationAdmin(admin.ModelAdmin):
    actions = (
        'send_welcome_emails',
    )

    def send_activate_emails(self, request, queryset):
        rows_affected = 0
        for obj in queryset:
            with transaction.commit_on_success():
                # send_email('welcome_email', request, obj) # send email via email service
                obj.status = 'activated'
                obj.save()
                rows_affected += 1

        self.message_user(request, 'sent %d' % rows_affected)

admin.site.register(MyUser, MyUserRegistrationAdmin)

视图.py

from library.models import Book

def get_books(limit=None, **filters):
    """ simple service function for retrieving books can be widely extended """
    return Book.objects.filter(**filters)[:limit]  # list[:None] will return the entire list

from library.services import get_books

class BookListView(ListView):
    """ simple view, e.g. implement a _build and _apply filters function """
    queryset = get_books()

def activate_user(user_id):
    user = User.objects.get(pk=user_id)

    # set active flag
    user.active = True
    user.save()

    # mail user
    send_mail(...)

    # etc etc

class ActivateUserForm(forms.Form):

    user_id = IntegerField(widget = UsernameSelectWidget, verbose_name="Select a user to activate")
    # the username select widget is not a standard Django widget, I just made it up

    def clean_user_id(self):
        user_id = self.cleaned_data['user_id']
        if User.objects.get(pk=user_id).active:
            raise ValidationError("This user cannot be activated")
        # you can also check authorizations etc. 
        return user_id

    def execute(self):
        """
        This is not a standard method in the forms API; it is intended to replace the 
        'extract-data-from-form-in-view-and-do-stuff' pattern by a more testable pattern. 
        """
        user_id = self.cleaned_data['user_id']

        user = User.objects.get(pk=user_id)

        # set active flag
        user.active = True
        user.save()

        # mail user
        send_mail(...)

        # etc etc

@register.filter
def friendly_name(user):
    return remote_api.get_cached_name(user.id)

def inactive_users():
    return User.objects.filter(active=False)


def users_called_publysher():
    for user in User.objects.all():
        if remote_api.get_cached_name(user.id) == "publysher":
            yield user 

class InactiveUserManager(models.Manager):
    def get_queryset(self):
        query_set = super(InactiveUserManager, self).get_queryset()
        return query_set.filter(active=False)

class InactiveUser(User):
    """
    >>> for user in InactiveUser.objects.all():
    …        assert user.active is False 
    """

    objects = InactiveUserManager()
    class Meta:
        proxy = True

class InactiveUserDistribution(models.Model):
    country = CharField(max_length=200)
    inactive_user_count = IntegerField(default=0)

class ActivateUserForm(forms.Form):
    # see above
   
    def execute(self):
        # see above
        query_model = InactiveUserDistribution.objects.get_or_create(country=user.country)
        query_model.inactive_user_count -= 1
        query_model.save()

user_activated = Signal(providing_args = ['user'])
user_deactivated = Signal(providing_args = ['user'])

class ActivateUserForm(forms.Form):
    # see above
   
    def execute(self):
        # see above
        user_activated.send_robust(sender=self, user=user)

class InactiveUserDistribution(models.Model):
    # see above

@receiver(user_activated)
def on_user_activated(sender, **kwargs):
        user = kwargs['user']
        query_model = InactiveUserDistribution.objects.get_or_create(country=user.country)
        query_model.inactive_user_count -= 1
        query_model.save()
    

import datetime

from djongo import models
from django.db.models.query import QuerySet
from django.contrib import admin
from django.db import transaction


class MyUser(models.Model):

    present_name = models.TextField(null=False, blank=True)
    status = models.TextField(null=False, blank=True)
    last_active = models.DateTimeField(auto_now=True, editable=False)

    # As mentioned you could put this in a template tag to pull it
    # from cache there. Depending on how it is used, it could be
    # retrieved from within the admin view or from a custom view
    # if that is the only place you will use it.
    #def get_present_name(self):
    #    # property became non-deterministic in terms of database
    #    # data is taken from another service by api
    #    return remote_api.request_user_name(self.uid) or 'Anonymous'

    # Moved to admin as an action
    # def activate(self):
    #     # method now has a side effect (send message to user)
    #     self.status = 'activated'
    #     self.save()
    #     # send email via email service
    #     #send_mail('Your account is activated!', '…', [self.email])

    class Meta:
        ordering = ['-id']  # Needed for DRF pagination

    def __unicode__(self):
        return '{}'.format(self.pk)


class MyUserRegistrationQuerySet(QuerySet):

    def for_inactive_users(self):
        new_date = datetime.datetime.now() - datetime.timedelta(days=3*365)  # 3 Years ago
        return self.filter(last_active__lte=new_date.year)

    def by_user_id(self, user_ids):
        return self.filter(id__in=user_ids)


class MyUserRegistrationManager(models.Manager):

    def get_query_set(self):
        return MyUserRegistrationQuerySet(self.model, using=self._db)

    def with_no_activity(self):
        return self.get_query_set().for_inactive_users()

# Then in model admin

class MyUserRegistrationAdmin(admin.ModelAdmin):
    actions = (
        'send_welcome_emails',
    )

    def send_activate_emails(self, request, queryset):
        rows_affected = 0
        for obj in queryset:
            with transaction.commit_on_success():
                # send_email('welcome_email', request, obj) # send email via email service
                obj.status = 'activated'
                obj.save()
                rows_affected += 1

        self.message_user(request, 'sent %d' % rows_affected)

admin.site.register(MyUser, MyUserRegistrationAdmin)

请注意，我通常将模型、视图和服务带到模块级和 根据项目的规模进一步分离

---

Django设计用于轻松交付网页。如果您对此不满意，也许您应该使用另一种解决方案

我正在模型上编写根操作或公共操作（以具有相同的接口），以及模型控制器上的其他操作。如果我需要其他模型的操作，我将导入其控制器

这种方法对我和我的应用程序的复杂性来说已经足够了

Hedde的响应是一个展示django和python本身灵活性的示例

---

这个问题很有趣

Django使用了一种稍微修改过的MVC。Django中没有“控制器”的概念。最接近的代理是“视图”，这往往会导致与MVC转换混淆，因为在MVC中，视图更像Django的“模板”

在Django中，“模型”不仅仅是数据库抽象。在某些方面，它与作为MVC控制器的Django的“视图”分担责任。它包含与实例关联的所有行为。如果该实例需要与外部API交互作为其行为的一部分，那么这仍然是模型代码。事实上，模型根本不需要与数据库交互，因此您可以想象模型完全作为外部API的交互层存在。这是一个更加自由的“模型”概念

然后，请注意不要过度设计，有时这只是浪费时间，会让人失去对重要事情的关注。不时地回顾一下这篇文章

查看活动项目

• 更多的人=更需要合理组织
• 它们有一个简单的结构
• 它们有一个straigtforward目录结构
• 这也是一个很好的一看
  • 您可以将所有模型放在应用程序/models/logicalgroup.py下

• e、 g

  用户

  ，

  组

  和相关模型可以放在

  你的应用程序/模型/用户.py下

• e、 g

  投票

  ，

  问题

  ，

  答案

  。。。可以在你的app/models/polls.py下进入

• 在

  你的应用程序/模型/\uuuuu init\uuuuuuuuuuupy的
  中加载你需要的内容

• 模型是您的数据
  • 这包括您的实际数据
  • 这还包括会话/cookie/cache/fs/index数据
• 用户与控制器交互以操纵模型
  • 这可以是API，也可以是保存/更新数据的视图
  • 这可以通过

    request.GET

    /

    request.POST

    等进行调整
  • 思考分页或过滤
• 数据将更新视图
  • 模板获取数据并相应地格式化
  • 甚至不带模板的API都是视图的一部分；e、 g.

    tastype

    或

    活塞

  • 这也应该考虑中间件

利用/

• 如果您需要为每个请求做一些工作，中间件是一种方法。
  • e、 g.添加时间戳
  • e、 g.更新有关页面点击率的指标
  • e、 g.填充缓存
• 如果您有一些代码片段总是在格式化对象时重复出现，那么templatetags很好。
  • e、 g.活动选项卡/url面包屑

利用

• 创建

  User

  可以进入

  UserManager（models.Manager）

• 实例的详细信息应该在

  models.Model

  上

• queryset

  的详细信息可以在

  models.Manager中找到

• 您可能希望一次创建一个

  用户

  ，因此您可能认为它应该位于模型本身上，但在创建对象时，您可能不具备所有详细信息：

例如：

class UserManager(models.Manager):
   def create_user(self, username, ...):
      # plain create
   def create_superuser(self, username, ...):
      # may set is_superuser field.
   def activate(self, username):
      # may use save() and send_mail()
   def activate_in_bulk(self, queryset):
      # may use queryset.update() instead of save()
      # may use send_mass_mail() instead of send_mail()

尽可能使用表格

很多样板代码都可以使用elimi