Django中外键model的互相读取

外键调用

先设定一个关系模型如下：

from django.db import models


class Blog(models.Model):
    name = models.CharField(max_length=100)
    tagline = models.TextField()

    def __str__(self):
        return self.name
 
class Author(models.Model):
    name = models.CharField(max_length=50)
    email = models.EmailField()

    def __str__(self):
        return self.name
 
class Entry(models.Model):
    blog = models.ForeignKey(Blog)
    headline = models.CharField(max_length=255)
    body_text = models.TextField()
    authors = models.ManyToManyField(Author)

    def __str__(self):   
        return self.headline

上面的数据关系很明晰，Entry中有Blog和Author的外键。
如果要在Entry中读取blog和author的数据很容易：

entry = Entry.objects.all()
for e in entry:
    blog = e.blog
    author = e.authors

要在Blog和Author中读取Entry也可以：

blog = Blog.objects.all()
entry = blog.entry_set.all()
 
author = Author.objects.all()
entry = author.entry_set.all()

下面通过entry使blog和author互相读取，比如要知道一个blog的Author只需如下：

blogs = Blog.objects.all()

for blog in blogs:
if blog.name == "我们想要查询的Author的name":
    author = blog. entry_set.authors

要查询一个author的所有blog如下：

authors = Author.objects.all()
blogs = []
 
for author in authors:
    if author.name== "我们想要查询的Author的name":
        for entry in author.entry_set.all():
            blogs.append(entry. blog)