Overview

Our GraphQL API isn't just about reading data, we need to make updates and manipulate data too!

In this lesson, we will:

• Set up a connector with a POST request that accepts a body
• Learn about how to craft a selection with nested properties

Create a listing

We're on to the last feature to implement in Airlock: creating a listing.

We'll need to add a mutation to our schema. On the REST API side, we'll be using the POST /listings endpoint. Since we can't try this out in the browser, here's what the curl request looks like:

And here's the shape of the data we receive:

Let's get to it!

Setting up the schema

Let's add the types and fields we need in the schema to make this feature come to life.

1. Open up the listings.graphql file and paste the schema below:

   listings.graphql

   input CreateListingInput {
     title: String!
     numOfBeds: Int!
     costPerNight: Float!
   }
   
   type CreateListingResponse {
     listing: Listing
   }
   
   type Mutation {
     createListing(input: CreateListingInput!): CreateListingResponse
   }

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We've added a mutation called createListing that takes in one argument called input. This input is a non-nullable CreateListingInput type, consisting of three fields: title, numOfBeds and costPerNight, all non-nullable fields. Finally, the mutation returns a CreateListingResponse type. CreateListingResponse has only one field: listing of type Listing.

That's it for our schema definition!

If we save our changes now, we'll get errors that should be familiar by now:

Adding a connector

Every root field needs a connector, so let's get to fixing those errors!

1. Append the @connect directive to the end of the field, defining the source as v1 as usual.

   listings.graphql

   createListing(input: CreateListingInput!): CreateListingResponse
     @connect(
       source: "v1"
       http: { GET: "" }
       selection: """
   
       """
     )

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2. We'll set up the http value, this time, let's change the GET call to a POST call to the /listings endpoint.

   listings.graphql

   http: {
    POST: "/listings"
   }

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3. This call needs a body! Let's add a body property to the http object. The value will be a mapping similar to what we've done before with selection.

   listings.graphql

   http: {
    POST: "/listings"
    body: """
    # TODO
    """
   }

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Crafting the body mapping

Let's look at the shape of the curl request needed for the POST /listings endpoint:

The value for --data reflects the shape we need to give the endpoint. A listing property set to an object with three properties: title, numOfBeds and costPerNight.

These are properties that already exist in our schema, specifically under the CreateListingInput type that gets passed in as an argument to the mutation.

And as we already know, we can access GraphQL argument values using $args. Let's put it all together.

1. Jump back to the listings.graphql file where we left off defining our body property.

   listings.graphql

   body: """
     # TODO
   """

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2. First, we need to start by defining the top-level listing property, followed by a colon (:)

   listings.graphql

   body: """
   listing:
   """

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   This maps the first level of our payload:

   curl request

   --data '{
      "listing": {
        "title": "New York GQL Summit in Space",
        "numOfBeds": 4,
        "costPerNight": 404
      }
    }'

3. Next, we need values for the three properties of the listing. Since these are all accessible from the $args.input, we'll start with defining that.

   listings.graphql

   body: """
   listing:
     $args.input
   """

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4. Then we'll access the fields inside input using curly brackets ({ }), defining title, numOfBeds, and costPerNight.

   listings.graphql

   body: """
   listing:
     $args.input {
       title
       numOfBeds
       costPerNight
     }
   """

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And we're all done with the POST request's body!

Crafting the selection mapping

If we save our changes now, we'll get an error:

We need a selection mapping to finish it off!

1. Jumping over to the selection property in our connector:

   listings.graphql

   createListing(input: CreateListingInput!): CreateListingResponse
      @connect(
      source: "v1"
      http: {
        POST: "/listings"
        body: """
        listing:
          $args.input {
            title
            numOfBeds
            costPerNight
          }
        """
        }
      selection: """
        # TODO
      """
      )

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2. This mutation needs to return a CreateListingResponse type, which contains a listing field that returns a Listing type. Let's first define the top-level listing: property, which will return an object.

   listings.graphql

   selection: """
   listing: {
     # TODO
   }
   """

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3. To help us craft this selection mapping, let's refer back to the response from our curl request:

   Response from curl request

   {
     "id": "06611dcd-f21f-4676-a02c-ad4b205c6d64",
     "title": "New York GQL Summit in Space",
     "description": "",
     "costPerNight": 404,
     "numOfBeds": 4,
     "hostId": "user-4",
     "locationType": "CAMPSITE",
     "photoThumbnail": "https://res.cloudinary.com/apollographql/image/upload/v1644353890/odyssey/federation-course2/illustrations/listings-10.png",
     "isFeatured": false,
     "closedForBookings": false,
     "latitude": null,
     "longitude": null
   }

   It looks like we have all the properties we need that map to all the fields in our Listing type!

4. Let's add all of those fields inside the curly brackets, making sure to rename closedForBookings to closed to match our schema.

   listings.graphql

   selection: """
   listing: {
     id
     title
     numOfBeds
     costPerNight
     closed: closedForBookings
   }
   """

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Running the mutation

Moment of truth! Let's check out http://localhost:4000 where the local router is running.

Let's build the mutation to create a listing.

We'll also need to provide the input in the Variables section:

Perfect, go ahead and run it! We should get data back with the details of our new listing, complete with an id generated from the REST API!

Practice

Key takeaways

• We can apply connectors to Mutation type fields just as we do for Query type fields.
• When submitting data to a POST endpoint, we'll most likely need to include a body property in our connector's http definition.
• To access the mutation field's input from inside the connector, we can use $args.input and define a selection of the properties to include.
• To build out our mutation field's response, we can use the selection property. From here we can access the response from the REST API and select the JSON properties we want to return.

Conclusion

Congratulations, you've successfully plugged an existing REST API into a graph using Apollo Connectors! 🎉

We worked with two schema directives to add connectors to our schema: @source, which we used to define a new data source for our connectors to use, and @connect, which let us define the specific instructions for "connecting" REST API data to a field.

We're now equipped with the tools needed for our developer workflow: using Rover for local supergraph development and Explorer to debug connector network calls and examine query plans. We've implemented a few pages for our project demo, Airlock, showcasing featured listings, a listing's details, and creating a listing. And we did all of this without writing a single line of resolver code!

So, where can you go from here?

• Publish your schema to GraphOS and take advantage of checks, observability, and proposals to bring your graph to production
• Expand your graph to use federation and include other subgraphs
• Go further with connectors, diving into more complex use cases such as using entities, federation directives, value transformations and more. Stay tuned for the next Odyssey course!

We'd also love to hear your feedback on Apollo Connectors. Drop us a note in the community forum!

See you in the next one!