Python 当两个外键指向同一个表时如何使用Factory boy

我试图使用Factory Boy链接两个Django模型，但我找不到解决此问题的简单解决方案。以下是具有相应工厂的模型：

class Currency(models.Model):
    id = models.CharField(max_length=3, primary_key=True)


class ConversionRate(models.Model):
    currency = models.ForeignKey(Currency, null=False, on_delete=models.CASCADE)
    quote = models.ForeignKey(Currency, null=False, on_delete=models.CASCADE)
    rate = models.DecimalField(max_digits=6, decimal_places=2)


class CurrencyFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = Currency

    id = factory.Sequence(lambda n: ['EUR', 'USD'][n%2])
    conversion_rate = factory.RelatedFactory('my_app.factories.ConversionRateFactory', 'currency')


class ConversionRateFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = ConversionRate

    currency = factory.SubFactory(CurrencyFactory)
    quote = factory.SubFactory(CurrencyFactory, id='EUR')
    rate = 1.2

这是测试表的默认内容：

+--------+   +--------------------------+ 
|Currency|   |       ConversionRate     |
+--------+   +----------+--------+------+ 
|   id   |   | currency |  quote | rate |
+--------+   +----------+--------+------+ 
|  EUR   |   |    USD   |  EUR   |  1.2 |
+--------+   +----------+--------+------+  
|  USD   |   |    EUR   |  EUR   |   1  |
+--------+   +----------+--------+------+  

当我尝试构建工厂时，将抛出完整性错误：

CurrencyFactory.create()
# Error:  UNIQUE constraint failed: Currency.id

我还尝试在CurrencyFactory的“Meta”部分中添加

django\u get\u或\u create=（'id'，）

，但这会创建一个无限循环

过去有人遇到过这样的问题吗？有什么建议吗

这是使用

django\u get\u或\u create=（'id'，）

时的回溯：

env/lib/python3.6/site-packages/factory/builder.py:272:in-build
步骤.解决（预处理）
env/lib/python3.6/site-packages/factory/builder.py:221:解析中
self.attributes[field\u name]=getattr（self.stub，field\u name）
env/lib/python3.6/site packages/factory/builder.py:375:in\uuu getattr__
额外=上下文，
env/lib/python3.6/site-packages/factory/declarations.py:324:in-evaluate
返回self.generate（步骤，默认值）
env/lib/python3.6/site-packages/factory/declarations.py:414:in-generate
返回步骤递归（子工厂，参数，强制顺序=强制顺序）
env/lib/python3.6/site-packages/factory/builder.py:233:in-recurse
返回builder.build（父步骤=自，强制顺序=强制顺序）
env/lib/python3.6/site-packages/factory/builder.py:299:in-build
上下文=后生成上下文，
env/lib/python3.6/site-packages/factory/declarations.py:675:in-call
返回步骤递归（工厂，已通过）
env/lib/python3.6/site-packages/factory/builder.py:233:in-recurse
返回builder.build（父步骤=自，强制顺序=强制顺序）
env/lib/python3.6/site-packages/factory/builder.py:272:in-build
步骤.解决（预处理）
env/lib/python3.6/site-packages/factory/builder.py:221:解析中
self.attributes[field\u name]=getattr（self.stub，field\u name）
env/lib/python3.6/site packages/factory/builder.py:375:in\uuu getattr__
额外=上下文，
env/lib/python3.6/site-packages/factory/declarations.py:324:in-evaluate
返回self.generate（步骤，默认值）
env/lib/python3.6/site-packages/factory/declarations.py:414:in-generate
返回步骤递归（子工厂，参数，强制顺序=强制顺序）
env/lib/python3.6/site-packages/factory/builder.py:233:in-recurse
返回builder.build（父步骤=自，强制顺序=强制顺序）
env/lib/python3.6/site-packages/factory/builder.py:279:内置
kwargs=kwargs，
env/lib/python3.6/site packages/factory/base.py:314:in实例化
返回self.factory.\u创建（模型，*args，**kwargs）
env/lib/python3.6/site-packages/factory/django.py:163:in\u-create
返回cls.\u获取或创建（模型类，*args，**kwargs）
env/lib/python3.6/site-packages/factory/django.py:154:in\u-get\u或\u-create
实例，_created=manager.get_或_create（*args，**键\u字段）
env/lib/python3.6/site-packages/django/db/models/manager.py:82:in-manager\u方法
返回getattr（self.get_queryset（），name）（*args，**kwargs）
env/lib/python3.6/site-packages/django/db/models/query.py:487:in-get\u或\u-create
返回self.get（**查找），False
env/lib/python3.6/site-packages/django/db/models/query.py:394:in-get
clone=self.filter（*args，**kwargs）
env/lib/python3.6/site-packages/django/db/models/query.py:836:in-filter
返回self.\u filter\u或\u exclude（False、*args、**kwargs）
env/lib/python3.6/site-packages/django/db/models/query.py:850:in\u-filter\u或\u-exclude
克隆=自我。_chain（）
env/lib/python3.6/site-packages/django/db/models/query.py:1156:in\u-chain
obj=自我。_克隆（）
env/lib/python3.6/site packages/django/db/models/query.py:1168:in\u clone
c=self.\uuuuu类（model=self.model，query=self.query.chain（），using=self.\u db，hints=self.\u hints）
env/lib/python3.6/site-packages/django/db/models/sql/query.py:337:in-chain
obj=self.clone（）
env/lib/python3.6/site-packages/django/db/models/sql/query.py:300:in-clone
obj.where=self.where.clone（）
env/lib/python3.6/site-packages/django/db/models/sql/where.py:148:in-clone
子项=[]，连接器=self.connector，否定=self.negated）
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
cls=，children=[]，connector='和'，negated=False
@类方法
def_新实例（cls，children=None，connector=None，negated=False）：
"""
创建新节点（或子类）时创建此类的新实例
该类的内部代码中需要。通常，它只是阴影
__但是，具有uu init_uu签名的子类
Node.\uuu init\uuuu的扩展可能需要实现此方法以
允许节点创建它们的新实例（如果它们有额外的
设置要做的事情）。
"""
>obj=节点（子节点、连接器、否定）
E RecursionError:调用Python对象时超出了最大递归深度

正如您所指出的，问题来自于

CurrencyFactory

创建

转换率工厂

，该工厂反过来创建2

CurrencyFactory

我建议使用

factory.Trait

通过递归禁用它：

在工厂

类参数

部分定义特征：启用时（通过设置布尔标志），它将添加附加的声明

为该特征设置一个默认值

True

：直接调用

CurrencyFactory

将添加一个

ConversionRate

在

转换率工厂中
    env/lib/python3.6/site-packages/factory/builder.py:272: in build
        step.resolve(pre)
    env/lib/python3.6/site-packages/factory/builder.py:221: in resolve
        self.attributes[field_name] = getattr(self.stub, field_name)
    env/lib/python3.6/site-packages/factory/builder.py:375: in __getattr__
        extra=context,
    env/lib/python3.6/site-packages/factory/declarations.py:324: in evaluate
        return self.generate(step, defaults)
    env/lib/python3.6/site-packages/factory/declarations.py:414: in generate
        return step.recurse(subfactory, params, force_sequence=force_sequence)
    env/lib/python3.6/site-packages/factory/builder.py:233: in recurse
        return builder.build(parent_step=self, force_sequence=force_sequence)
    env/lib/python3.6/site-packages/factory/builder.py:299: in build
        context=postgen_context,
    env/lib/python3.6/site-packages/factory/declarations.py:675: in call
        return step.recurse(factory, passed_kwargs)
    env/lib/python3.6/site-packages/factory/builder.py:233: in recurse
        return builder.build(parent_step=self, force_sequence=force_sequence)
    env/lib/python3.6/site-packages/factory/builder.py:272: in build
        step.resolve(pre)
    env/lib/python3.6/site-packages/factory/builder.py:221: in resolve
        self.attributes[field_name] = getattr(self.stub, field_name)
    env/lib/python3.6/site-packages/factory/builder.py:375: in __getattr__
        extra=context,
    env/lib/python3.6/site-packages/factory/declarations.py:324: in evaluate
        return self.generate(step, defaults)
    env/lib/python3.6/site-packages/factory/declarations.py:414: in generate
        return step.recurse(subfactory, params, force_sequence=force_sequence)
    env/lib/python3.6/site-packages/factory/builder.py:233: in recurse
        return builder.build(parent_step=self, force_sequence=force_sequence)
    env/lib/python3.6/site-packages/factory/builder.py:279: in build
        kwargs=kwargs,
    env/lib/python3.6/site-packages/factory/base.py:314: in instantiate
        return self.factory._create(model, *args, **kwargs)
    env/lib/python3.6/site-packages/factory/django.py:163: in _create
        return cls._get_or_create(model_class, *args, **kwargs)
    env/lib/python3.6/site-packages/factory/django.py:154: in _get_or_create
        instance, _created = manager.get_or_create(*args, **key_fields)
    env/lib/python3.6/site-packages/django/db/models/manager.py:82: in manager_method
        return getattr(self.get_queryset(), name)(*args, **kwargs)
    env/lib/python3.6/site-packages/django/db/models/query.py:487: in get_or_create
        return self.get(**lookup), False
    env/lib/python3.6/site-packages/django/db/models/query.py:394: in get
        clone = self.filter(*args, **kwargs)
    env/lib/python3.6/site-packages/django/db/models/query.py:836: in filter
        return self._filter_or_exclude(False, *args, **kwargs)
    env/lib/python3.6/site-packages/django/db/models/query.py:850: in _filter_or_exclude
        clone = self._chain()
    env/lib/python3.6/site-packages/django/db/models/query.py:1156: in _chain
        obj = self._clone()
    env/lib/python3.6/site-packages/django/db/models/query.py:1168: in _clone
        c = self.__class__(model=self.model, query=self.query.chain(), using=self._db, hints=self._hints)
    env/lib/python3.6/site-packages/django/db/models/sql/query.py:337: in chain
        obj = self.clone()
    env/lib/python3.6/site-packages/django/db/models/sql/query.py:300: in clone
        obj.where = self.where.clone()
    env/lib/python3.6/site-packages/django/db/models/sql/where.py:148: in clone
        children=[], connector=self.connector, negated=self.negated)

    _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

    cls = <class 'django.db.models.sql.where.WhereNode'>, children = [], connector = 'AND', negated = False

        @classmethod
        def _new_instance(cls, children=None, connector=None, negated=False):
            """
                Create a new instance of this class when new Nodes (or subclasses) are
                needed in the internal code in this class. Normally, it just shadows
                __init__(). However, subclasses with an __init__ signature that aren't
                an extension of Node.__init__ might need to implement this method to
                allow a Node to create a new instance of them (if they have any extra
                setting up to do).
                """
    >       obj = Node(children, connector, negated)
    E       RecursionError: maximum recursion depth exceeded while calling a Python object

class CurrencyFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = models.Currency
        django_get_or_create = ['id']

    class Params:
        with_conversion_rate = factory.Trait(
            conversion_rate=factory.RelatedFactory('my_app.factories.ConversionRateFactory', 'currency'),
        )

    # Small improvement: use a `factory.Iterator` to cycle between value
    id = factory.Iterator(['EUR', 'USD'])
    # By default, force each CurrencyFactory to create a ConversionRate.
    with_conversion_rate = True

class ConversionRateFactory(factory.django.DjangoModelFactory):
    class Meta:
        model = models.ConversionRate

    rate = 1.2
    currency = factory.SubFactory(
        CurrencyFactory,
        with_conversion_rate=False,
    )
    quote = factory.SubFactory(
        CurrencyFactory,
        id='EUR',
        with_conversion_rate=False,
    )