Private Fields

Private (external) fields can provide local context for later resolution. These fields will act as plain fields so will not be exposed in the GraphQL API.

Some uses include:

• Context that relies upon field inputs.

• Avoiding fully materializing an object hierarchy (lazy resolution)

Defining a private field

Specifying a field with strawberry.Private[...] will desigate it as internal and not for GraphQL.

Example

Consider the following type, which can accept any Python object and handle converting it to string, representation, or templated output:

@strawberry.type
class Stringable:
    value: strawberry.Private[object]

    @strawberry.field
    def string(self) -> str:
        return str(self.value)

    @strawberry.field
    def repr(self) -> str:
        return repr(self.value)

    @strawberry.field
    def format(self, template: str) -> str:
        return template.format(my=self.value)

The Private[...] type lets Strawberry know that this field is not a GraphQL field. “value” is a regular field on the class, but it is not exposed on the GraphQL API.

@strawberry.type
class Query:
    @strawberry.field
    def now(self) -> Stringable:
        return Stringable(value=datetime.datetime.now())

Queries can then select the fields and formats desired, but formatting only happens as requested:

{
  now {
    format(template: "{my.year}")
    string
    repr
  }
}

---

{
  "data": {
    "now": {
      "format": "2022",
      "string": "2022-09-03 17:03:04.923068",
      "repr": "datetime.datetime(2022, 9, 3, 17, 3, 4, 923068)"
    }
  }
}