Mutations

A Mutation is a special ObjectType that also defines an Input.

Quick example

This example defines a Mutation:

import graphene

class CreatePerson(graphene.Mutation):
    class Input:
        name = graphene.String()

    ok = graphene.Boolean()
    person = graphene.Field(lambda: Person)

    def mutate(self, args, context, info):
        person = Person(name=args.get('name'))
        ok = True
        return CreatePerson(person=person, ok=ok)

person and ok are the output fields of the Mutation when is resolved.

Input attributes are the arguments that the Mutation CreatePerson needs for resolving, in this case name will be the only argument for the mutation.

mutate is the function that will be applied once the mutation is called.

So, we can finish our schema like this:

# ... the Mutation Class

class Person(graphene.ObjectType):
    name = graphene.String()

class MyMutations(graphene.ObjectType):
    create_person = CreatePerson.Field()

schema = graphene.Schema(mutation=MyMutations)

Executing the Mutation

Then, if we query (schema.execute(query_str)) the following:

mutation myFirstMutation {
    createPerson(name:"Peter") {
        person {
            name
        }
        ok
    }
}

We should receive:

{
    "createPerson": {
        "person" : {
            name: "Peter"
        },
        "ok": true
    }
}

InputFields and InputObjectTypes

InputFields are used in mutations to allow nested input data for mutations

To use an InputField you define an InputObjectType that specifies the structure of your input data

import graphene

class PersonInput(graphene.InputObjectType):
    name = graphene.String()
    age = graphene.Int()

class CreatePerson(graphene.Mutation):
    class Input:
        person_data = graphene.InputField(PersonInput)

    person = graphene.Field(lambda: Person)

    def mutate(self, args, context, info):
        p_data = args.get('person_data')

        name = p_data.get('name')
        age = p_data.get('age')

        person = Person(name=name, age=age)
        return CreatePerson(person=person)

Note that name and age are part of person_data now

Using the above mutation your new query would look like this:

mutation myFirstMutation {
    createPerson(personData: {name:"Peter", age: 24}) {
        person {
            name,
            age
        }
    }
}

InputObjectTypes can also be fields of InputObjectTypes allowing you to have as complex of input data as you need

import graphene

class LatLngInput(graphene.InputObjectType):
    lat = graphene.Float()
    lng = graphene.Float()

#A location has a latlng associated to it
class LocationInput(graphene.InputObjectType):
    name = graphene.String()
    latlng = graphene.InputField(LatLngInput)