get all children of category id in a list drf-CodePudding

I have a model like this

class Catgeory(models.Model):
      name = models.CharField()
      parent = models.ForeignKey('self', related_name='children')

Now I need to write a piece of code to return a list of all children ids for a specified category

for example, I have a category like that

General (id=1) --> Electronics (id=2) --> Mobile phones (id=3) --> Apple (id=4)

If I want to get children of Electronics it should return [3, 4] But I have been trying to find a solution for 3 hours, unfortunately, I could not solve it yet. I can get all parents by one child but cannot get children by a parent. If anybody has a solution or any idea, can you help? Any help would be appreciated! Thank you very much!

CodePudding user response：

you can try this

class Catgeory(models.Model):
    name = models.CharField()
    parent = models.ForeignKey('self', related_name='children')
    
    def get_all_child(self):
        children = []
        for u in self.children.all():
            children.append(u.get_all_child())
        return children

But you have to be sure that you do not have this (child==parent) because if you have this kind of case you will have an infinite loop.Be carefull.

CodePudding user response：

To get all child categories we can try bfs approach

models.py

class Catgeory(models.Model):
    name = models.CharField(max_length=60)
    parent = models.ForeignKey('self', related_name='children', on_delete=models.SET_NULL, null=True, blank=True)

views.py

from django.http.response import HttpResponse
from .models import Catgeory

# Create your views here.
def index(request):
    category        = Catgeory.objects.get(id=1)
    child_category  = Catgeory.objects.filter(parent=category)
    queue = list(child_category)
    while(len(queue)):
        next_children = Catgeory.objects.filter(parent=queue[0])
        child_category = child_category.union(next_children)
        queue.pop(0)
        queue = queue   list(next_children)
    return HttpResponse(child_category)