Django在另外两个人之间共享一个模型

Question

我建立了一个系统来审查葡萄酒和食物。我很快发现自己重复模型和模板，但差异很小。

从根本上看，我想要一个审查，以涉及食品或葡萄酒。每种食物或葡萄酒都可以有很多评论。

我有一个FK（目前的方式），只留下一个空白，但鉴于他们如此相似，我决定这不是明智的。

然后，我去了抽象模型，至少能够字段化字段（新方法），但是因为我无法链接到通用项目模型，所以对于同一个问题我有一个稍微优雅的代码库。

研究到这我想知道从食品和葡萄酒到审查的一般关系是要去的方式或内容类型，但我不明白他们如何工作，或者如果他们是我是什么寻找。

电流的方式 - 葡萄酒有品牌，食品都有专卖店和评论有食品和葡萄酒

class Brand(models.Model): 
    brand_name = models.CharField(max_length=30) 
    location = models.ForeignKey(Location, null=True,blank=True) 

import datetime 
YEAR_CHOICES = [] 
for r in range(2005, (datetime.datetime.now().year+1)): 
    YEAR_CHOICES.append((r,r)) 
YEAR_CHOICES = list(reversed(YEAR_CHOICES)) 

class Wine(models.Model): 
    wine_name = models.CharField(max_length=30) 
    wine_type = models.ForeignKey(WineType) 
    wine_year = models.IntegerField(choices=YEAR_CHOICES, default=datetime.datetime.now().year) 

    brand = models.ForeignKey(Brand) 

class Store(models.Model): 
    store_name = models.CharField(max_length=30) 

    def __str__(self): 
     return self.store_name 

class Food(models.Model): 
    food_name = models.CharField(max_length=30) 
    food_desc = models.CharField(blank=True,max_length=100) 

    store = models.ForeignKey(Store) 

    def __str__(self): 
     return self.store.store_name +' - '+self.food_name 

class Review(models.Model): 
    rating = models.CharField(max_length=30) 
    value = models.CharField(max_length=30) 
    date = models.DateField(auto_now_add=True) 
    person = models.ForeignKey(Person) 
    comment = models.CharField(blank=True,max_length=100) 
    food = models.ForeignKey(Food, blank=True,default=None,null=True) 
    wine = models.ForeignKey(Wine, blank=True,default=None,null=True) 

    class Meta(): 
     ordering = ['-date'] 

新途径 - 葡萄酒和食品的物品，商店和专卖店的来源，但评论仍需要两葡萄酒和食品

class Source(models.Model): 
    name = models.CharField(max_length=30) 
    desc = models.CharField(blank=True,max_length=100) 
    class Meta: 
     abstract = True 

class Item(models.Model): 
    name = models.CharField(max_length=30) 
    desc = models.CharField(blank=True,max_length=100) 

    class Meta: 
     abstract = True 



class WineSource(Source): 
    location = models.ForeignKey(Location, null=True,blank=True) 
    class Meta(): 
     ordering = ['location', 'name'] 

class FoodSource(Source): 
    def __str__(self): 
     return self.name 

import datetime 
YEAR_CHOICES = [] 
for r in range(2005, (datetime.datetime.now().year+1)): 
    YEAR_CHOICES.append((r,r)) 
YEAR_CHOICES = list(reversed(YEAR_CHOICES)) 

class Wine(Item): 

    wine_type = models.ForeignKey(WineType) 
    wine_year = models.IntegerField(choices=YEAR_CHOICES, default=datetime.datetime.now().year) 

    source = models.ForeignKey(WineSource) 

    def __str__(self): 
     return self.source.name +' '+self.name+ ' ' + str(self.wine_type)+ ' '+ str(self.wine_year) 

class Food(Item): 


    source = models.ForeignKey(FoodSource) 

    def __str__(self): 
     return self.source.name +' - '+self.name 

class Review(models.Model): 
    rating = models.CharField(max_length=30) 
    value = models.CharField(max_length=30) 
    date = models.DateField(auto_now_add=True) 
    person = models.ForeignKey(Person) 

    food = models.ForeignKey(Food, blank=True,default=None,null=True) 
    wine = models.ForeignKey(Wine, blank=True,default=None,null=True) 
    #Doesn't work as it's abstract- item = models.ForeignKey(Item,null=True) 

    class Meta(): 
     ordering = ['-date'] 

Answer 1

我觉得Generic Foreign Key就是答案。例如：

from django.db import models 
from django.contrib.contenttypes.fields import GenericForeignKey 
from django.contrib.contenttypes.models import ContentType 

class Product(models.Model): 
    ... 

class Food(Product): 
    ... 

class Wine(Product): 
    ... 

class Review(models.Model): 
    ... 

    content_type = models.ForeignKey(ContentType) 
    object_id = models.PositiveIntegerField() 
    content_object = GenericForeignKey('content_type', 'object_id') 

这使我们可以将审阅与项目中任何模型的任何单个记录相关联。 content_type字段跟踪您尝试关联的模型（在这种情况下为Food或Wine）。 object_id现场跟踪记录在我们试图跟踪的Wine或Food表中。 content_object是一个便利的属性，允许我们直接访问对象（一旦保存了评论）。

当创建一个新的检视刚分配Wine或Food到content_object领域：

wine = Wine.objects.get(...) 
review = Review(..., content_object=wine) 
review.save() 

Answer 2

你也可以为Item使用Multi-table inheritance代替AbstractClass的。然后你可以在Review中设置一个直接ForeignKey到Item。 您还可以结合InheritanceManager此：

from model_utils.managers import InheritanceManager 

class Item(models.Model): 
    name = models.CharField(max_length=30) 
    desc = models.CharField(blank=True,max_length=100)  

    objects = InheritanceManager()  

class Wine(Item): 

    wine_type = models.ForeignKey(WineType) 
    wine_year = models.IntegerField(choices=YEAR_CHOICES, default=datetime.datetime.now().year) 

    source = models.ForeignKey(WineSource) 

    def __str__(self): 
     return self.source.name +' '+self.name+ ' ' + str(self.wine_type)+ ' '+ str(self.wine_year) 


class Food(Item): 

    source = models.ForeignKey(FoodSource) 

    def __str__(self): 
     return self.source.name +' - '+self.name 

class Review(models.Model): 
    rating = models.CharField(max_length=30) 
    value = models.CharField(max_length=30) 
    date = models.DateField(auto_now_add=True) 
    person = models.ForeignKey(Person) 

    item = models.ForeignKey(Item,null=True) 

    class Meta(): 
     ordering = ['-date'] 

然后你就可以过滤这样的：

wine_reviews = Review.objects.exclude(item__wine__isnull=True) 

food_reviews = Review.objects.exclude(item__food__isnull=True) 

# and all item (directly sub-classed as wine or food: 
items = Item.objects.select_subclasses().all()