3. Mutations

Now that we have attached datasources to our Query in the schema let’s try to do the same for Mutation.

1. Update Schema

type Mutation {
  addReview(text: String, userId: String): Review
  deletReview(reviewId: String): String
}

We’ll update the Mutatation type as above where we’ll add two operations

• addReview: Which accepts two arguments (i.e text and userId) and adds a new review by making a POST request to http://localhost:4001/reviews endpoint, which expects something like the following in the request payload

{
    "id": "1", // UserId of the user posting review 
    "text": "New Review by John Doe11" // review text
}

• deleteReview: Which accepts one argument (i.e reviewId), that deletes a review by making a DELETE request to http://localhost:4001/reviews/:reviewId

2. Configure datasource.

Follow these steps to configure a data source for the Mutation.

• Navigate to schema tab in the api where you would see the split screen view of schema editor on left and list of configurable fields on right
• Select addReview field from Mutation type
• Select REST option
• Set a unique datasource name
• Set the URL as http://localhost:4001/reviews
• Select method type as POST
• Set request body to relay the graphql arguments to our upstream payload as follows:

{
  "text": "{{.arguments.text}}",
  "userId": "{{.arguments.userId}}"
  }

• Update the API

3. Execute mutation operation

We can now test our mutation operation with the playground in API designer using the following operation

mutation AddReview {
  addReview(text: "review using udg", userId:"1"){
    id
    text
  }
}

That should return us the following response:

{
  "data": {
    "addReview": {
      "id": "e201e6f3-b582-4772-b95a-d25199b4ab82",
      "text": "review using udg"
    }
  }
}

Challenge

Configure a datasource to delete a review using review id.

Notes

- For users field on type Review
- - Description :: delete review using reviewId
- - URL :: http://localhost:4001/reviews/:reviewId
- - Method :: DELETE

- Enable field mapping to map your API response 

Now that we have a good idea how we could do CRUD operations with UDG APIs, let’s see how we can secure them using policies