GraphQL 查询具有多个嵌套解析器并将字段映射到 arguments

Question

From GraphQL Client's perspective, how do I perform a query with multiple nested resolvers where the fields from the parent are passed as arguments to the child resolver?

Here is a minimal example:

GraphQL Schema:

type Author {
  id: ID!
  name: String!
}

type Book {
  id: ID!
  title: String!
  releaseDate: String!
}


type Query {
  // Returns a list of Authors ordered by name, 'first' indicates how many entries to return
  getAllAuthors(first: Int!): [Author]!
  // Returns a list of Books ordered by releaseDate, 'first' indicates how many entries to return
  getBooksByAuthorId(first: Int! authorId: ID!): [Book]!
}

Is it possible to write a query to get all authors and their last released book? Something around the lines:

query GetAuthorsWithLastBook($first: Int!) {
  getAllAuthors(first: $first) {
    authorId: id
    name
    lastBook: getBooksByAuthor(1, authorId) {
      title
    }
  }
}

In the example above, I attempted to alias getAllAuthors.id as authorId and pass the alias down as argument to getBooksByAuthor(...) but that didn't work.

The key aspect of the problem is that I don't know the authorId s beforehand. I could fetch the authors first and build a query to fetch their last book but that will result in multiple queries and that is something I would like to avoid.

Update

A Java Kickstarter example is available here:https://www.graphql-java-kickstart.com/tools/schema-definition/

Answer 1

yes, on the graphql definition, you need to add lastBook in the Author

type Author {
  id: ID!
  name: String!
  lastBook: [Book]
}

Next up u need to write the resolver for the lastBook

const resolvers = {
  Query: {
    Author {
      lastBook: (parent, args) {
        const userId = parent.id;
        return getBooksByAuthor(userId, 1);
      },
    }
  }
};