Calling a custom method in a Graphene python resolver

Question

Hello I simply want to avoid repeating code for each query, and I was wondering if I could call a method from inside a resolver a such:

# pseudo code
class Query(graphene.ObjectType):

    field = graphene.Field(SomeType)

    def do_boring_task(parent, info, arg):
        
        return "I did something"

    def resolve_field(parent, info):

        did_something = parent.do_boring_task(arg) # <-- is this possible ?
        
        # do something here

        return resolved_fields

I always get a "graphql.error.located_error.GraphQLLocatedError: 'NoneType' object has no attribute 'do_boring_task'" error

Is it possible to do that the way I described it, or is this something that should be done using middleware?

Thanks

score 4 · Accepted Answer · answered Sep 14 '21 at 07:04

Classes inheriting from graphene.ObjectType are different than a normal class, resolve_field and do_boring_task are by default static methods.

Note that first argument of resolve_field is parent and not self, do_boring_task is a classmethod (static method in other languages) of Query class and does not exist in parent schema, that explains your error.

A quick fix for your problem is as shown below, define the function, outside of the class.

def do_boring_task(args):
    return "I did something"

class Query(graphene.ObjectType):
    field = graphene.Field(SomeType)

    def resolve_field(parent, info):
        did_something = do_boring_task(arg)       
        # do something here
        return resolved_fields

Refer these in the blog for more details

Implicit Static Method

Resolvers Outside the class

Calling a custom method in a Graphene python resolver

1 Answers1