如何为具有外键的模型创建序列化器来访问外键表数据?

Question

我想使用序列化器以更有效的方式重写以下API。在下面的API中，用户和组是外键。

我想使用Serializer返回组和用户的所有匹配数据。

如何为这种情况设计序列化器

@api_view(['GET'])
def get_post(request, group_id, post_type, post_limit):
if request.method == 'GET':
print('group id = ')
print(group_id)
# data = GroupPostsModel.objects.filter(
#     group_id=group_id) & GroupPostsModel.objects.filter(post_type=post_type).order_by('-time_stamp')
try:
data = GroupPostsModel.objects.filter(
group_id=group_id, post_type=post_type).order_by('-time_stamp')[post_limit:post_limit+3]
# data = data[0:3] model.objects.filter(book = 'bible')
post_arr_obj = []
for post in data:
comments_count = GroupPostCommentsModel.objects.filter(
post_id=post.id).count()
print('post id = '+str(post.id))
post_dict = {
'post_id': str(post.id),
'post_text': str(post.post_text),
'post_type': str(post.post_type),
'image': str(post.image),
'document': str(post.document),
'likes': str(post.likes),
'group_id': str(post.group.id),
'user_id': str(post.user.id),
'time_stamp': str(post.time_stamp),
'profile_pic': str(post.user.profile_pic),
'first_name': str(post.user.first_name),
'last_name': str(post.user.last_name),
'gender': str(post.user.gender),
'comments_count': str(comments_count)
}
post_arr_obj.append(post_dict)
except Exception as e:
print('get_post exception : '+str(e))
resp = {
'resp': post_arr_obj
}
# group_post_serializer = GroupPostsSerializer(data, many=True)
return Response(resp)
else:
return Response({'msg': 'Only GET request allowed..!'})

一个用户可以加入/创建多个组

一个组可以有多个帖子

一个用户可以发布多个帖子

UserModel

class UserModel(models.Model):
first_name = models.CharField(max_length=20)
last_name = models.CharField(max_length=20)
gender = models.CharField(max_length=6)
college_name = models.CharField(max_length=50)
user_id = models.CharField(max_length=30,unique = True)
user_password = models.CharField(max_length=20)
profile_pic = models.ImageField(blank=True, null=True, upload_to='profile_pic/')
class Meta:
db_table = 'user'

GroupModel

class GroupsModel(models.Model):
group_name = models.CharField(max_length=20, unique=True)
group_description = models.CharField(max_length=50)
group_joining_link = models.CharField(max_length=50, default='', unique=True)
user_id = models.ManyToManyField(UserModel, through='UserModelGroupsModel', related_name='u_g')
class Meta:
db_table = 'groups'

GroupPostsModel

class GroupPostsModel(models.Model):
post_text = models.CharField(max_length=1000)
post_type = models.CharField(max_length=20)
image = models.ImageField(blank=True, null=True, upload_to='post_images/')
document = models.FileField(blank=True,null=True, upload_to='post_documents/')
likes = models.IntegerField(default=0)
time_stamp = models.DateTimeField(auto_now=True)
group = models.ForeignKey(GroupsModel, on_delete=models.CASCADE)
user = models.ForeignKey(UserModel, on_delete=models.CASCADE)
def delete(self):
if self.image:
if os.path.isfile(self.image.path):
os.remove(self.image.path)
if self.document:
if os.path.isfile(self.document.path):
os.remove(self.document.path)

super().delete()

class Meta:
db_table = 'group_posts'

Answer 1

你可以使用Django Rest FrameworkModelSerializer来做这件事。使用模型GroupPostsModel

创建序列化器

class GroupPostsSerializer(serializers.ModelSerializer):
id = IntegerField()
post_text = CharField()
...
group_id = IntegerField(source="group.id")
...
class Meta:
model = GroupPostsModel
fields = [
'id'
'post_text'
...
]

对于comments_count，您可以使用SerializerMethodField()来定义序列化器将用于该字段的方法。

用posts初始化序列化器

serializer = GroupPostsSerializer(data, many=True)

然后访问数据

resp = {
'resp': serializer.data
}