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310 lines
7.9 KiB
ReStructuredText
310 lines
7.9 KiB
ReStructuredText
.. _Scalars:
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Scalars
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=======
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Scalar types represent concrete values at the leaves of a query. There are
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several built in types that Graphene provides out of the box which represent common
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values in Python. You can also create your own Scalar types to better express
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values that you might have in your data model.
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All Scalar types accept the following arguments. All are optional:
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``name``: *string*
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Override the name of the Field.
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``description``: *string*
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A description of the type to show in the GraphiQL browser.
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``required``: *boolean*
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If ``True``, the server will enforce a value for this field. See `NonNull <../list-and-nonnull.html#nonnull>`_. Default is ``False``.
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``deprecation_reason``: *string*
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Provide a deprecation reason for the Field.
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``default_value``: *any*
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Provide a default value for the Field.
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Built in scalars
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----------------
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Graphene defines the following base Scalar Types that match the default `GraphQL types <https://graphql.org/learn/schema/#scalar-types>`_:
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``graphene.String``
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^^^^^^^^^^^^^^^^^^^
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Represents textual data, represented as UTF-8
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character sequences. The String type is most often used by GraphQL to
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represent free-form human-readable text.
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``graphene.Int``
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^^^^^^^^^^^^^^^^
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Represents non-fractional signed whole numeric
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values. Int is a signed 32‐bit integer per the
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`GraphQL spec <https://facebook.github.io/graphql/June2018/#sec-Int>`_
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``graphene.Float``
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^^^^^^^^^^^^^^^^^^
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Represents signed double-precision fractional
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values as specified by
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`IEEE 754 <http://en.wikipedia.org/wiki/IEEE_floating_point>`_.
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``graphene.Boolean``
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^^^^^^^^^^^^^^^^^^^^
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Represents `true` or `false`.
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``graphene.ID``
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^^^^^^^^^^^^^^^
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Represents a unique identifier, often used to
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refetch an object or as key for a cache. The ID type appears in a JSON
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response as a String; however, it is not intended to be human-readable.
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When expected as an input type, any string (such as `"4"`) or integer
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(such as `4`) input value will be accepted as an ID.
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----
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Graphene also provides custom scalars for common values:
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``graphene.Date``
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^^^^^^^^^^^^^^^^^
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Represents a Date value as specified by `iso8601 <https://en.wikipedia.org/wiki/ISO_8601>`_.
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.. code:: python
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import datetime
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from graphene import Schema, ObjectType, Date
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class Query(ObjectType):
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one_week_from = Date(required=True, date_input=Date(required=True))
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def resolve_one_week_from(root, info, date_input):
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assert date_input == datetime.date(2006, 1, 2)
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return date_input + datetime.timedelta(weeks=1)
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schema = Schema(query=Query)
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results = schema.execute("""
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query {
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oneWeekFrom(dateInput: "2006-01-02")
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}
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""")
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assert results.data == {"oneWeekFrom": "2006-01-09"}
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``graphene.DateTime``
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^^^^^^^^^^^^^^^^^^^^^
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Represents a DateTime value as specified by `iso8601 <https://en.wikipedia.org/wiki/ISO_8601>`_.
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.. code:: python
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import datetime
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from graphene import Schema, ObjectType, DateTime
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class Query(ObjectType):
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one_hour_from = DateTime(required=True, datetime_input=DateTime(required=True))
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def resolve_one_hour_from(root, info, datetime_input):
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assert datetime_input == datetime.datetime(2006, 1, 2, 15, 4, 5)
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return datetime_input + datetime.timedelta(hours=1)
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schema = Schema(query=Query)
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results = schema.execute("""
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query {
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oneHourFrom(datetimeInput: "2006-01-02T15:04:05")
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}
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""")
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assert results.data == {"oneHourFrom": "2006-01-02T16:04:05"}
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``graphene.Time``
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^^^^^^^^^^^^^^^^^
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Represents a Time value as specified by `iso8601 <https://en.wikipedia.org/wiki/ISO_8601>`_.
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.. code:: python
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import datetime
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from graphene import Schema, ObjectType, Time
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class Query(ObjectType):
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one_hour_from = Time(required=True, time_input=Time(required=True))
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def resolve_one_hour_from(root, info, time_input):
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assert time_input == datetime.time(15, 4, 5)
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tmp_time_input = datetime.datetime.combine(datetime.date(1, 1, 1), time_input)
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return (tmp_time_input + datetime.timedelta(hours=1)).time()
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schema = Schema(query=Query)
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results = schema.execute("""
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query {
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oneHourFrom(timeInput: "15:04:05")
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}
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""")
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assert results.data == {"oneHourFrom": "16:04:05"}
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``graphene.Decimal``
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^^^^^^^^^^^^^^^^^^^^
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Represents a Python Decimal value.
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.. code:: python
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import decimal
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from graphene import Schema, ObjectType, Decimal
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class Query(ObjectType):
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add_one_to = Decimal(required=True, decimal_input=Decimal(required=True))
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def resolve_add_one_to(root, info, decimal_input):
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assert decimal_input == decimal.Decimal("10.50")
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return decimal_input + decimal.Decimal("1")
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schema = Schema(query=Query)
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results = schema.execute("""
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query {
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addOneTo(decimalInput: "10.50")
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}
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""")
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assert results.data == {"addOneTo": "11.50"}
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``graphene.JSONString``
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^^^^^^^^^^^^^^^^^^^^^^^
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Represents a JSON string.
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.. code:: python
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from graphene import Schema, ObjectType, JSONString, String
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class Query(ObjectType):
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update_json_key = JSONString(
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required=True,
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json_input=JSONString(required=True),
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key=String(required=True),
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value=String(required=True)
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)
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def resolve_update_json_key(root, info, json_input, key, value):
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assert json_input == {"name": "Jane"}
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json_input[key] = value
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return json_input
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schema = Schema(query=Query)
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results = schema.execute("""
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query {
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updateJsonKey(jsonInput: "{\\"name\\": \\"Jane\\"}", key: "name", value: "Beth")
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}
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""")
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assert results.data == {"updateJsonKey": "{\"name\": \"Beth\"}"}
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``graphene.Base64``
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^^^^^^^^^^^^^^^^^^^
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Represents a Base64 encoded string.
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.. code:: python
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from graphene import Schema, ObjectType, Base64
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class Query(ObjectType):
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increment_encoded_id = Base64(
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required=True,
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base64_input=Base64(required=True),
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)
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def resolve_increment_encoded_id(root, info, base64_input):
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assert base64_input == "4"
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return int(base64_input) + 1
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schema = Schema(query=Query)
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results = schema.execute("""
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query {
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incrementEncodedId(base64Input: "NA==")
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}
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""")
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assert results.data == {"incrementEncodedId": "NQ=="}
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Custom scalars
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--------------
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You can create custom scalars for your schema.
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The following is an example for creating a DateTime scalar:
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.. code:: python
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import datetime
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from graphene.types import Scalar
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from graphql.language import ast
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class DateTime(Scalar):
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'''DateTime Scalar Description'''
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@staticmethod
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def serialize(dt):
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return dt.isoformat()
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@staticmethod
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def parse_literal(node):
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if isinstance(node, ast.StringValue):
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return datetime.datetime.strptime(
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node.value, "%Y-%m-%dT%H:%M:%S.%f")
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@staticmethod
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def parse_value(value):
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return datetime.datetime.strptime(value, "%Y-%m-%dT%H:%M:%S.%f")
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Mounting Scalars
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----------------
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Scalars mounted in a ``ObjectType``, ``Interface`` or ``Mutation`` act as
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``Field``\ s.
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.. code:: python
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class Person(graphene.ObjectType):
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name = graphene.String()
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# Is equivalent to:
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class Person(graphene.ObjectType):
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name = graphene.Field(graphene.String)
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**Note:** when using the ``Field`` constructor directly, pass the type and
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not an instance.
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Types mounted in a ``Field`` act as ``Argument``\ s.
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.. code:: python
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graphene.Field(graphene.String, to=graphene.String())
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# Is equivalent to:
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graphene.Field(graphene.String, to=graphene.Argument(graphene.String))
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