Custom ConnectionField in graphene - relay

Question

I'm not understanding how to use custom fields in a ConnectionField in graphene. I have something like:
class ShipConnection(Connection):
extra = String()
class Meta:
node = Ship
SHIPS = ['Tug boat', 'Row boat', 'Canoe']
class Query(AbstractType):
ships = relay.ConnectionField(ShipConnection)
def resolve_ships(self, args, context, info):
return ShipConnection(
extra='Some extra text',
edges=???
)
Normally, you'd say:
def resolve_ships(self, args, context, info):
return SHIPS
but how do you return something in extra and return a list?

Answer 1

The answer turns out to be to use an undocumented class method of graphene's ConnectionField class, called resolve_connection. The following works:
def resolve_ships(self, args, context, info):
field = relay.ConnectionField.resolve_connection(
ShipConnection,
args,
SHIPS
)
field.extra = 'Whatever'
return field

Answer 2

The proper way to do this is exactly explained here.
class Ship(graphene.ObjectType):
ship_type = String()
def resolve_ship_type(self, info):
return self.ship_type
class Meta:
interfaces = (Node,)
class ShipConnection(Connection):
total_count = Int() # i've found count on connections very useful!
def resolve_total_count(self, info):
return get_count_of_all_ships()
class Meta:
node = Ship
class Edge:
other = String()
def resolve_other(self, info):
return "This is other: " + self.node.other
class Query(graphene.ObjectType):
ships = relay.ConnectionField(ShipConnection)
def resolve_ships(self, info):
return get_list_of_ships_from_database_or_something_idk_its_your_implmentation()
schema = graphene.Schema(query=Query)
I don't know if this is recommended, but the resolve_total_count method can also be implemented as:
def resolve_total_count(self, info):
return len(self.iterable)
I don't know if the iterable property is documented anywhere, but I was able to find it while investigating the Connection class