在执行验证时向Django模型序列化程序添加提取字段

Question

假设我有以下模型，和模型序列化器：

模型。派克

class Approve(models.Model):
    process = models.IntegerField(verbose_name='Associated Process')
    content = models.CharField(max_length=300, verbose_name="Approval Content")

serializers.py

class ApproveSerializer(serializers.ModelSerializer):
    class Meta:
        model = Approve
        fields = ('id', 'process' ,'content')
    def validate(self, value):
        process = value['process']
        try:
            something_else = Something.objects.get(process)
        except Something.DoesNotExist:
            raise serializers.ValidationError('Invalid Process')
        return value

问题是我想在views.py中使用这个对象something_else，而不是进行另一个数据库查询。有什么方法可以通过串行化程序传递它，而不会在调用serializer.is_valid（）方法时导致串行化程序验证错误。

Answer 1

我想出了解决这个问题的方法。

serializers.py

class ApproveSerializer(serializers.ModelSerializer):
    class Meta:
        model = Approve
        fields = ('id', 'process' ,'content')
    def validate(self, value):
        process = value['process']
        try:
            something_else = Something.objects.get(process)
            value['something_else'] = something_else
        except Something.DoesNotExist:
            raise serializers.ValidationError('Invalid Process')
        return value

意见。在调用序列化程序之前。方法，则应弹出已添加到序列化程序的值。

def post(self, request):
    serializer = ApproveSerializer(data=request.data)
    if serializer.is_valid():
        something_else = serializer.validated_data.pop('something_else')
        something_else.property = new_property
        something_else.save()
        serializer.save()
    else:
        # Error handling goes here serialzier.errors

我不确定这是一个好的做法，但至少现在对我来说是有效的。希望知道更好的解决办法。

Answer 2

我不确定你的views.py看起来怎么样，但本质上，你需要在那里实例化序列化器：

def approve_view(request):
    if request.method == "POST":
        process = request.POST.get('value', None)
        something_else = Something.objects.filter(process=process).first()
        serializer = ApproveSerializer(something_else=something_else) # This is where you pass the something_else object. 
        if serializer.is_valid():
             # Your code for successful validation.
        else:
             # Your code for failed validation

现在，您已经将something_else传递到ProveSerializer，您需要将其设置为属性：

class ApproveSerializer(serializers.ModelSerializer):
    def __init__(self, something_else=None):
        self.something_else = something_else

    class Meta:
        model = Approve
        fields = ('id', 'process' ,'content')

    def validate(self, value):
        process = value['process']
        if not self.something_else:
             raise serializers.ValidationError('Invalid Process')
    return value