Django创建关系

Question

如何将几个不同的类别添加到News？

class Categories(models.Model): 

title = models.CharField(max_length=100) 
c_date = models.DateTimeField('date published') 
url_code =models.URLField() 
def __unicode__(self): return self.title 



class News(models.Model): 
title = models.CharField(max_length=100) 
content= models.TextField() 
categories = models.ForeignKey(Categories) 
c_date = models.DateTimeField('date published')  
     image =models.ImageField(upload_to = 'img/', 
      default ='img/None/no-img.jpg')  
url_code =models.URLField() 

def __unicode__(self): return self.title 

Answer 1

现在，你只能有每一个类别新闻项目;因为您的数据库关系被定义为一对一。

要使新闻项目可以有多个类别，请将关系更改为ManyToMany。

class News(models.Model): 
    categories = models.ManyToManyField(Category) 

现在，类别添加到新闻：

n = News() 
c = Category.objects.get(pk=1) # fetch one category 
n.save() # Save the news item first 
n.categories.add(c) # add the category for the news item 
c = Category.objects.get(pk=2) # fetch another 
n.categories.add(c) 
n.save() 

要提取的每个类别，那么所有的新闻条目标签与该类别：

当我尝试显示

c = Category.objects.all() 
for category in c: 
    for news in category.news_set.all(): 
     print(news) 

Answer 2

使用ManyToManyField：

class News(models.Model): 
    .... 
    categories = models.ManyToManyField(Categories) 

UPDATE：要输出的类别列表中使用如下代码：

{% for news in news_list %} 
    <h4>{{ news.title }}</h4> 
    <div> 
     Categories: 
     {% for category in news.categories.all %} 
      {{ category.title }} 
     {% endfor %} 
    </div> 
{% endfor %}