Django-REST中关联字段上的KeyError [英] KeyError on relation field in Django-REST

问题描述

我有以下型号:

  class ProductColor(models.Model):color_title = models.CharField(max_length = 50)class BasicProduct(models.Model):product_title = models.CharField(max_length = 150)product_desc = models.TextField()product_price = models.FloatField(默认= 10.0)#描述此产品可用的颜色product_colors = models.ManyToManyField(ProductColor)class BasicCartItem(models.Model):cart_product = models.ForeignKey(BasicProduct)cart_color = models.ForeignKey(ProductColor，blank = True，默认= None，null = True) 

还有我的ModelSerializer:

 类CartSerializer(serializers.ModelSerializer):类Meta:模型= models.BasicCartItem 

我在此输入我的看法:

  {'cart_product':1} 

然后运行代码:

  m = CartSerializer(数据=输入数据)如果m.is_valid():items = m.data#生成KeyError:u'cart_color' 

堆栈跟踪的提取:

 文件"python2.7/site-packages/rest_framework/serializers.py"，行430，在to_representation中属性= field.get_attribute(实例)get_attribute中的第103行的文件"python2.7/site-packages/rest_framework/relations.py"返回get_attribute(instance，self.source_attrs)get_attribute中的第69行的文件"python2.7/site-packages/rest_framework/fields.py"实例=实例[attr]KeyError:u'cart_color' 

任何知识渊博的人都知道这里发生了什么事?我已经在这里呆了几个小时，我不知道自己在做什么错.

谢谢.

解决方案

您以错误的方式访问数据.您应该访问序列化程序上的 .validated_data 而不是 .data .

  m = CartSerializer(数据=输入数据)如果m.is_valid():items = m.validated_data#在此处访问经过验证的数据 

为什么 serializer.data 方法不适用于您的情况?

在执行 .data 时，由于尚未传递 instance 参数，因此序列化程序将尝试序列化 initial_data .它将期望所有字段都存在，但是由于数据上不存在 cart_color ，因此它将引发 KeyError .

然后通常什么时候应该使用 serializer.data ?

序列化现有对象时，通常应使用 serializer.data .这将要求您在创建序列化程序的实例时传递 instance 参数.

  m = CartSerializer(instance = my_object)items = m.data#序列化对象时使用.data 

I have the following models:

class ProductColor(models.Model):
    color_title = models.CharField(max_length=50)

class BasicProduct(models.Model):

    product_title = models.CharField(max_length=150)
    product_desc = models.TextField()
    product_price = models.FloatField(default=10.0)

    # Describes what colors are available for this product
    product_colors = models.ManyToManyField(ProductColor)

class BasicCartItem(models.Model):
    cart_product = models.ForeignKey(BasicProduct)
    cart_color = models.ForeignKey(ProductColor, blank=True, default=None, null=True)

And my ModelSerializer:

class CartSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.BasicCartItem

I'm giving my view this input:

{'cart_product': 1}

Then running the code:

    m = CartSerializer(data=inputdata)
    if m.is_valid():
        items = m.data # Generates KeyError: u'cart_color'

Extract of stacktrace:

  File "python2.7/site-packages/rest_framework/serializers.py", line 430, in to_representation
    attribute = field.get_attribute(instance)
  File "python2.7/site-packages/rest_framework/relations.py", line 103, in get_attribute
    return get_attribute(instance, self.source_attrs)
  File "python2.7/site-packages/rest_framework/fields.py", line 69, in get_attribute


  instance = instance[attr]
KeyError: u'cart_color'

Anyone with good knowledge knows what's going on here? I've been stuck here for hours and I don't know what I'm doing wrong..

Thanks.

解决方案

You are accessing the data in a wrong way. You should access .validated_data on the serializer instead of .data.

m = CartSerializer(data=inputdata)
if m.is_valid():
    items = m.validated_data # access validated data here

Why serializer.data approach did not work for your case?

When you are doing .data, the serializer will try to serialize the initial_data as you have not passed the instance argument. It will expect all the fields to be present but since cart_color is not present on the data, it will raise a KeyError.

When should you generally use serializer.data then?

You should generally use serializer.data when you are serializing an existing object. This would require you to pass an instance argument when creating an instance of the serializer.

m = CartSerializer(instance=my_object)
items = m.data # use .data when serializing an object

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