How to handle nullable reference in graphql?

@samara 

In GraphQL, nullable fields are handled by defining the type of a field as nullable in the schema definition. This means that the field can return a null value in addition to its defined type.

To handle nullable references in GraphQL, you can follow these steps:

1. Define the schema: In the schema definition, specify which fields can return a null value by using the GraphQLNonNull wrapper type. For example, if a field can return a null value, define it like this:

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type User {
  id: ID!
  name: String
}

In this example, the "name" field can return a null value because it is not required to have a value.

1. Handle null values in the resolver functions: In your resolver functions, check for null values and handle them accordingly. For example, if a field can return a null value, you can return null directly from the resolver function:

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Query: {
  getUser: (root, args, context, info) => {
    const user = getUser(args.id);

    if (!user) {
      return null;
    }

    return user;
  }
}

By explicitly checking for null values in the resolver functions, you can ensure that the GraphQL response reflects the nullable nature of your fields.

Overall, handling nullable references in GraphQL involves defining the schema to allow for null values and handling these null values in your resolver functions to provide a consistent and reliable API.