Server Side GraphQL using Node

GraphQL is basically a spec that describes a declarative query language that your clients can use to ask an API for the exact data that they want . GraphQL achieves this by creating strongly typed Schema for you API ( gives ultimate flexibility )

Bascially on the server side ,GraphQL is compose of these common terms :-

• Type Definitions
• Resolvers
• Query Definitions
• Mutation Definitions
• Composition
• Schema

On the Client Side ,GraphQL is composed of these common terms :-

• Queries
• Mutations
• Fragments

Where does GraphQL fit in ?

The graphQL server can fit into different scenarios example

• A server with DB connected
• A GraphQL server as layer in front of many 3rd party services and connects them all in one GraphQL API
• A hybrid approach where GraphQL server has a connected DB and also communicates with 3rd party services

Key Parts of a GraphQL schema

• Types - a construct defining a shape with fields
• Fields - keys on a Type that have a name and a value type
• Scalars - primitive value type built into GraphQL
• Query - type that defines how clients can access data
• Mutation - type that defines how clients can modify or create data

Queries and Resolvers

Below are the basic steps that are followed while creating Queries

• Create Query Type in Schema using SDL
• Add fields to the Query Type
• Create resolvers for that fields

  type User {
    email: String!
    avatar: String
    friends: [User]!
  }

  type Query {
    me: User
  }

Resolvers are responsible from returning the values for fields that exists on types in a schema . The execution of a resolver is dependent on the incoming client queries

Below are the things to keep in mind about resolvers :-

• Resolver name must match the exact field name on the schema type
• It must return the value type declared for the matching field
• Resolvers can be async
• Can retrieve data from any source

In GraphQL Server + Resolvers = Server

Basically to create a minimum server , we need a Query type with a field and a resolver for that field