如何使石墨烯输入类变量可选？答案

【问题标题】：How to make Graphene Input Class variables optional?如何使石墨烯输入类变量可选？
【发布时间】：2018-02-02 22:39:24
【问题描述】：

在 GraphQL 更新突变中，我希望能够传入子对象的值，但我希望这些值中的每一个都是可选的。

所以我创建了一个这样的输入类：

class CityCouncilInput(graphene.InputObjectType):
  mayor = graphene.String()
  treasurer = graphene.String()

现在，我希望能够为市长和财务主管传递任一值，或者只传递其中一个值。

请知道，如果传入所有值，我的代码可以正常工作。我只希望这些字段值是可选的。我该怎么做？

罗伯特

【问题讨论】：

标签： graphene-python

【解决方案1】：

你可以试试

class CityCouncilInput(graphene.InputObjectType):
  mayor = graphene.String(required=False, default=None)
  treasurer = graphene.String(required=False, default=None)

【讨论】：

default_value 获取最新版本的graphene

【解决方案2】：

我认为最简单的方法是为突变函数定义一个默认参数

假设您有以下模型，其中您的值可以为空（注意：我假设 mayor 和 treasurer 都可以为空，但 NULL 不能为空 - 否则我猜你可以将None 作为默认参数传递）：

class CityCouncil(models.Model):
    mayor = models.TextField(max_length=1000, blank=True)
    treasurer = models.CharField(max_length=1000, blank=True)

然后创建市议会，这应该可行：

class createCityCouncil(graphene.Mutation):
    mayor = graphene.String()
    treasurer = graphene.String()

    class Arguments:
        mayor = graphene.String()
        treasurer = graphene.String()

    def mutate(self, mayor="", treasurer=""):

        council = CityCouncil(mayor=mayor, treasurer=treasurer)
        council.save()

        return createCityCouncil(
            mayor=council.mayor, 
            treasurer=council.treasurer
        )

同样，在执行更新突变时，您可以传入可选参数并选择性地使用setattr 更新对象的属性。

class updateCityCouncil(graphene.Mutation):
    mayor = graphene.String()
    treasurer = graphene.String()

    class Arguments:
        mayor = graphene.String()
        treasurer = graphene.String()

    def mutate(self, info, id, **kwargs):
        this_council=CityCouncil.objects.get(id=id)
        if not this_council:
            raise Exception('CityCouncil does not exist')

        for prop in kwargs:
            setattr(this_council, prop, kwargs[prop])

        this_council.save

        return updateCityCouncil(
            mayor=this_council.mayor, 
            treasurer=this_council.treasurer
        )

【讨论】：

【解决方案3】：

您可能只需要在您的 mutate 函数中运行一个 if 语句来更新任一字段，并且类 updateCityCouncil 突变的代码如下（PS：注意名为 CityCouncil 和 GraphQL 的模型的假设模型的类型）：

    class CityCouncilType(DjangoObjectType):
        class Meta:
            model = CityCouncil

    class CityCouncilInput(graphene.InputObjectType):
        id = graphene.Int()
        mayor = graphene.String()
        treasurer = graphene.String()

    class updateCityCouncil(graphene.Mutation):
        class Arguments:
            id = graphene.Int(required=True)
            input = CityCouncilInput(required=True)

        ok = graphene.Boolean()
        council = graphene.Field(CityCouncilType)

        @staticmethod
        def mutate(root, info, id, input=None):
            ok = False
            this_council = CityCouncil.objects.get(pk=id)
            if this_council:
                ok = True
                if input.mayor is not None:
                    this_council.mayor = input.mayor
                if input.treasurer is not None:
                    this_council.treasurer = input.treasurer
                this_council.save()
                return updateCityCouncil(ok=ok, council=this_council)
            return updateCityCouncil(ok=ok, council=None)

【讨论】：