GraphQL- Schema

In a previous post, I talked about GraphQL basics and how it can help one simplify fetching data for service over REST. Here, we will take the next step and under the concept of schema in GraphQL.

When starting to code a GraphQL backend, the first thing one needs to define is a schema. GraphQL provides us with Schema definition language or SDL which is used to define the schema.

Lets define a simple entity

type Person {
  id: ID!
  name: String!
  age: Int!

Here we are defining a simple person Model, which has three fields id, name, which is a string, and age, which is an integer. The “!” mark indicates that this is a required field.

Just defining the Person model does not expose any functionality, to expose the functionality, GrpahQL provides us with three root types, namely, Query, Mutation, and Subscription.

type Query 
   person(id: ID!): Person

The query mentioned above explains how a client can send an ID and gets a Person object in return.

Next, we have mutations that can help one implement remaining CRUD operations like create, update and delete.

type Mutation {
  createPerson(name: String!, age: Int!): Person!
  updatePerson(id: ID!, name: String!, age: String!): Person!
  deletePerson(id: ID!): Person!

Finally, one can define subscriptions, which will make sure whenever an event like the creation of a new object, updation or deletion happens, the server sends a message to the subscribing client.

type Subscription {
  newPerson: Person!
  updatedPerson: Person!
  deletedPerson: Person!

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