如何为使用石墨烯-django的突变定义自定义输出类型? [英] How can I define custom output types for mutations with graphene-django?

问题描述

创建/删除/更新/删除(CRUD)突变通常返回相应的数据库模型实例作为突变的输出类型.但是，对于非CRUD突变，我想定义特定于业务逻辑的突变输出类型.例如.返回列表元素的数量+不能在graphql类型和db模型之间一对一映射的ID列表.如何使用 graphene-django 实现此目标?

Create/remove/update/delete (CRUD) mutations usually return the corresponding database model instance as output type of the mutation. However for non-CRUD mutations I'd like to define business logic specific mutation output types. E.g. returning the count of list elements + a list of IDs which cannot be mapped 1-to-1 between graphql type and db models. How can I achieve this with graphene-django?

推荐答案

与模型无关的列表

要返回计数和元素列表时，可以创建一个自定义类型:

List not related to Models

As you want to return both a count and a list of elements, you can create a custom type:

class ListWithCountType(graphene.Scalar):

    @staticmethod
    def serialize(some_argument):
        # make computation here
        count = ...
        some_list = ...
        return { "count": count, "list": some_list }

然后在您的突变中按如下方式使用它:

Then on your mutation you use it like this:

class MyMutation(graphene.Mutation):
    list_with_count = graphene.Field(ListWithCountType)

    @classmethod
    def mutate(cls, root, info, **kwargs):
        some_argument = kwargs.pop("some_argument")
        return cls(list_with_count=some_argument)

添加到您的架构:

class Query(graphene.ObjectType):
    my_mutation = MyMutation.Field()

应返回以下内容:

{
  "data": {
    "list_with_count": {
      "count": <COUNT VALUE>,
      "list": <SOME_LIST VALUE>
    }
  }
}

* PS:如果仅是输出，那么可以.但是，如果希望将此类型作为参数，则除了"serialize"之外，还应该实现"parse_literal"和"parse_value".

*PS: if this is only an output, ok. But if you want this type to be an argument, you should also implement "parse_literal" and "parse_value", besides the "serialize".

此处是一个与表单一起使用的自定义ErrorType的示例.

Here is an example with a custom ErrorType used with forms.

来自在您的架构上:

import graphene

import cookbook.ingredients.schema


class Query(cookbook.ingredients.schema.Query, graphene.ObjectType):
    pass

schema = graphene.Schema(query=Query)

然后您可以查询:

query {
  allCategories {
    id
  }
}

应返回以下内容:

{
  "data": {
    "allCategories": [
      {
        "id": "1",
      },
      {
        "id": "2",
      },
      {
        "id": "3",
      },
      {
        "id": "4",
      }
    ]
  }
}

这是一个带有用户模型的示例.

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