Introduction to GraphQL

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Introduction to Data Driven Apps with GraphQL
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App Data Challenges
Data requirements
vary across devices
and become harder
when multiple
users share data
Users want instant
access to data
Building scalable
data-driven apps
without learning
distributed systems
concepts is hard
Users want to
continue using
their apps even
with low or no
connectivity

App Data Requirements
Real-time
Collaboration
Offline Programming
Model with Sync
Get Only the
Data You Need
Fine-grained
Access Control
Flexible Database
Options
Share Schema between
Client and Server

Option 1: HTTP or REST API
• Resources defined by “Endpoints”
• Client calls to many endpoints
• Uses HTTP as a transport
• Conceptually simple
• Tried and true

Option 1: HTTP or REST API
Real-time
Collaboration
Offline Programming
Model with Sync
Get Only the
Data You Need
Fine-grained
Access Control
Flexible Database
Options
Client and Server

Option 2: GraphQL
GraphQL is a query language for APIs and a runtime
for fulfilling those queries with your existing data.
GraphQL provides a complete and understandable description
of the data in your API, gives clients the power to ask for
exactly what they need and nothing more, makes it easier to
evolve APIs over time, and enables powerful developer tools
graphql.org/learn

GraphQL is a query language for APIs…
• Resources defined by a GraphQL Schema
• Client sends query, server orchestrates data
• Mutiple transports (HTTP, MQTT, WebSockets)
• Efficient (Network Bandwidth, Dev Time)
• Self Documenting (Introspection w/ Tooling)

GraphQL is a query language for APIs…
Queries read data
Mutations write data
Subscriptions are pushed data in real-time

Option 2: GraphQL
Real-time
Collaboration
Offline Programming
Model with Sync
Get Only the
Data You Need
Fine-grained
Access Control
Flexible Database
Options
Client and Server

GraphQL: Query Basics
There are 3 operation types:
• Query
• Mutation
• Subscription
Variables are optional. When using
variables, clients send a “variables” object
containing the values alongside the query.

A runtime for fulfilling those queries…
• A GraphQL server takes a query and returns a response of
the exact same shape.
• Each field in the query selection set is “resolved” by a
server side function.
• GraphQL provides a standard contract allowing clients to
talk to any number of backend data stores.

query {
posts {
id
title
comments {
content
}
author {
name
}
}
}
Posts resolves by Elasticsearch
Comments resolved by DynamoDB
Author resolved by custom Lambda

query {
posts {
id
title
comments {
content
}
author {
name
}
}
}
{
"data": {
"posts": [
{
"id": 1,
"title" "Intro to GraphQL",
"comments": [
{
"content": "I want GraphQL!"
}
],
"author": {
"name": "Awesome Developer"
}
}
]
}
}

GraphQL provides a description of your data…
• Define schema with schema definition language (SDL)
• Advanced types
– Object, Interface, Union, Enum, Input, Scalar
• Self documenting
• Code generation

Selection sets
Selection sets specify what fields to
resolve and thus what data to return
Selection sets can be nested
arbitrarily
Fields that return a scalar or an enum
do not have selection sets

Fragments
Fragments are a basic unit of
composition
Like a named, reusable selection set
but with a few extra features

Directives
@skip & @include supported
by the specification but system
implementations can add their
own

Schema Definition Language (SDL)
Concise way to define and document
GraphQL schemas
You can think of SDL as the Data
Definition Language (DDL) and the
query language as the Data
Manipulation Language (DML)

Scalars
Create scalar types with custom
validation, parsing, and serialization
Use Cases: email, timestamps, phone
numbers, any regex checked string

Objects
Contain a set of fields each of which
is of a specific type
A very common building block
Root types (Query, Mutation,
Subscription) are also Object types

Enumerations
Denotes a scalar that is of a
predetermined set of values

Interfaces
Defines a common set of fields.
Object types implement interfaces.
Query with fragments

Unions
A union says than an object is one of
a set of types.
Query with fragments

Gives clients the power to ask for what they need…
• Each UI component has its own data requirements
• The same backend model can be viewed in different ways
• The network is precious
• The security boundary should be defined by the backend, not the UI
• A queryable API is a better solution than different endpoints per view

Use case: Master-detail views
DetailMaster

Makes it easier to evolve APIs over time…
• GraphQL requires that every request specify every field
• We know what is being used = we can deprecate with confidence
• Schema allows for marking fields as deprecated!

Powerful Developer Tools
• Optimized, caching and offline client libraries
• Introspection
• Code generation
• IDE integrations
• Data visualizations

Demo: GraphQL In Action

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Introduction to GraphQL

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