Why do Appsync Mutations return null

Question

Hello,

I have a basic schema in AppSync for an API

```
type Location {
	id: Int!
}

type Mutation {
	pushLocation(id: Int!): Location
}

type Query {
	getLocation(id: Int!): Location
}

type Subscription {
	subscribeToLocation(id: Int!): Location
		@aws_subscribe(mutations: ["pushLocation"])
}

schema {
	query: Query
	mutation: Mutation
	subscription: Subscription
}
```

and with a simple mutation

```
mutation MyMutation {
  pushLocation(id: 10) {
    id
  }
}
```

but every time I run the mutation in the query console area I get a null response as below

```
{
  "data": {
    "pushLocation": null
  }
}
```

however, using the default AppSync API example & schema, the mutation always returns a response

What am I missing? I've compared the 2 API's carefully and their configurations are the same.

Thanks in advance

Regards,

Jason

Vaibhav J · Accepted Answer

Hi. This is most likely because you do not have a resolver set for your mutation. Try following steps -

1. In AppSync console, in left navigation, click on "Schema"
2. On next page, in right section under "Resolvers", search for Mutation list
3. Next to `publish(...): Channel`, click on "Attach" button
4. On next page, change resolver type to VTL.
5. From DataSource dropdown, select NoneDataSource.
6. Click Create
7. Under Configure Mapping Template, change to following code -

```
{
    "version": "2017-02-28",
    "payload": {
        "id": "$context.arguments.id"
    }
}
```

8. Click Save
9. Go back to Queries page and retest.

To make this work with your business logic you will have to implement resolvers. Read more here - https://docs.aws.amazon.com/appsync/latest/devguide/resolver-components.html

Why do Appsync Mutations return null

Relevant content