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In this module, we build the functionality to have the client be able to query for a list of listings.

Server Project#

src/graphql/typeDefs.ts#

We created a single root-level listings field that can be queried from the client to receive the information for a list of listings. The listing query field returns a collection of listings that satisfies three input arguments:

• limit: The amount of listing objects to be returned for a single page.

• page: The page (i.e. subset) of listing objects to be returned from the "listings" collection.

• filter: The filter (i.e. sort) to be applied to the list of listings returned.

  type Query {

    authUrl: String!

    user(id: ID!): User!

    listing(id: ID!): Listing!

    listings(filter: ListingsFilter!, limit: Int!, page: Int!): Listings!

  }

The ListingsFilter Enum determines the different filter values that can be applied to the listings query field. We've established two separate filter values:

• PRICE_LOW_TO_HIGH: To sort the listings from the lowest price to the highest price.

• PRICE_HIGH_TO_LOW: To sort the listings from the highest price to the lowest price.

  enum ListingsFilter {

    PRICE_LOW_TO_HIGH

    PRICE_HIGH_TO_LOW

  }

src/graphql/resolvers/Listing/index.ts#

In the listingResolvers map in the src/graphql/resolvers/Listing/index.ts file, we created the root-level query listings() resolver function to find a paginated list of listings from the "listings" collection based on the argument values provided.

    listings: async (

      _root: undefined,

      { filter, limit, page }: ListingsArgs,

      { db }: { db: Database }

    ): Promise<ListingsData> => {

      try {

        const data: ListingsData = {

          total: 0,

          result: []

        };