Resolvers define how GraphQL fields are fetched. In Nestipy, a resolver is a class decorated with @Resolver() and composed of @Query(), @Mutation(), and @ResolveField() handlers.

Resolver Basics

from typing import Annotated
from nestipy.graphql import Resolver, Query, ResolveField, Args, Parent
from nestipy.graphql.strawberry import ObjectType


@ObjectType()
class Cat:
    id: str
    name: str


@Resolver(of=Cat)
class CatsResolver:
    @Query()
    async def cat(self, id: Annotated[str, Args("id")]) -> Cat:
        return Cat(id=id, name="Misty")

    @ResolveField()
    async def name(self, root: Annotated[Cat, Parent()]) -> str:
        return root.name.upper()

Field Resolvers

Use @ResolveField() to compute a field based on the parent object. This is useful when you want to lazy-load nested data.

@ResolveField()
async def owner(self, root: Cat) -> Owner:
    return await self.owner_service.find_by_cat_id(root.id)

Using Guards

Resolvers support @UseGuards() and ExecutionContext just like HTTP controllers:

from nestipy.common import UseGuards


@Resolver(of=Cat)
@UseGuards(AuthGuard)
class CatsResolver:
    @Query()
    async def cat(self, id: Annotated[str, Arg()]) -> Cat:
        return Cat(id=id, name="Misty")

Tips

• Keep resolver logic thin and call providers for heavy logic.
• Use ResolveField for nested data to avoid over-fetching.
• Use guards or interceptors when access control is required.