GraphQL

main principle - code on the browser forms a query describing the data wanted and sends it to the API with a HTTP POST request -- all queries are sent to same address.

GraphQL schema

• contract between the server and client
• abstraction layer that provides flexibily to consumers and hide back-end implementation
• defines what API can and can't do; how clients can request or change data
• collection of object types containing fields
• schema describes two types:
  1. object type containing scalar types - leaves of the graph (concrete data)
  2. query type - tells what kind of queries can be made to API - direct link between query and returned JSON object

• [GraphQL Benefits]
• [GraphQL Fragment]
• [3 Types of GraphQL Operations]
• [GraphQL Server Approaches]
• [Example of Using Fetch API for GraphQL request]
• [Use GraphQL Variables to Do Queries]

Apollo server

• [Apollo Server]

• [Define Resolver for Object within Object]

• [Using DataLoader with Apollo Server] to solve n + 1 problem

• [Subscriptions on Apollo Server]

• context returns object and give to all resolvers as third parameter

• context is the right place to do things which are shared by multiple resolvers i.e. user identification

Apollo Client

Apollo client is a state management library to use GraphQL to interact with remote server. Client enables you to manage local state alongside remotely fetched state. A single API to interact with all of the application's state. ¹

• [Apollo Client Working with Cache]
• [Use Update Callback in useMutation to Manage Cache]
• [Subscriptions on Apollo Client]

[React] hooks:

• [UseQuery vs. UseLazyQuery]
• [useLazyQuery in useFffect Hook]
• [UseMutation]