from rest_framework import serializers
from .models import Brand


class BrandSerializer(serializers.ModelSerializer):
    """
    品牌序列化器
    """
    material_count = serializers.SerializerMethodField()

    class Meta:
        model = Brand
        fields = ['id', 'name', 'description', 'created_at', 'updated_at', 'material_count']
        read_only_fields = ['id', 'created_at', 'updated_at', 'material_count']

    def get_material_count(self, obj):
        return obj.materials.count()