Circular dependencies

Python is not able to resolve circular dependencies for schemas with recursive types.

e.g

  # category_type.py
  from .post_type import Post
  class Category(graphene.ObjectType):
    Post = graphene.List(Post)

  # post_type.py
  from .category_type import Category
  class Post(graphene.ObjectType):
    category = graphene.Field(Category)

At runtime, the above fails as the types haven’t yet loaded before being used in field definitions. A better option would be to wrap the field definitions in a lambda to be called at resolve time and after the types have been declared.

e.g

  # category_type.py
-  from .post_type import Post
  class Category(graphene.ObjectType):
-   Post = graphene.List(Post)
+   Post = lambda: graphene.List(Post)

+ from .post_type import Post

  # post_type.py
- from .category_type import Category
  class Post(graphene.ObjectType):
-   category = graphene.Field(Category)
+   category = lambda: graphene.Field(Category)

+ from .category_type import Category

cc @Globegitter

[sanfilippopablo]

Looking at some unrelated docs here it seems like you can do this:

graphene.List(lambda: MyCircularType)
graphene.Field(lambda: MyCircularType)

I just tested it and it works.

[syrusakbary]

Hi @imranolas,

You can achieve this by using String references (ala Django):

# category_type.py
@schema.register
class Category(graphene.ObjectType):
    Post = graphene.List('Post')

# post_type.py
@schema.register
class Post(graphene.ObjectType):
    category = graphene.Field('Category')