记一次：ORM查询到数据后，返回前端前，对数据做出修改

from app01.models import BusinessOpportunities, UserRecommendSetting


class BusinessOpportunitiesSerializer(serializers.ModelSerializer):
    quantity = serializers.SerializerMethodField(method_name=None, read_only=True)   # 字段初始化

    class Meta:
        model = BusinessOpportunities
        fields = (‘bo_id‘, ‘bo_name‘, ‘keywords‘, ‘quantity‘, ‘quantity_unit‘, ‘tel‘, ‘url‘)     # 序列化

    def get_quantity(self, obj):   # 针对初始化后的字段做出修改
        if obj.get(‘quantity‘) == -1:
            return ‘-‘    # 满足条件的值，把数据修改为  ‘-’
        return obj.get(‘quantity‘)   # 返回原始数据（不满足上述条件，返回本身数据库查出的值）


class BusinessOpportunitiesDetailSerializer(serializers.ModelSerializer):
    quantity = serializers.SerializerMethodField(method_name=None, read_only=True)

    class Meta:
        model = BusinessOpportunities
        fields = ‘__all__‘

    def get_quantity(self, obj):
        if obj.quantity == -1:
            return ‘-‘
        return obj.quantity