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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Slides for
APIs — Ruby on Rails Guides
</title>
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<!-- Any section element inside of this container is displayed as a slide -->
<div class="slides">
<section>
<h1>APIs</h1><p>After working through this guide you will:</p>
<ul>
<li>know about the thinking behind GraphQL APIs</li>
<li>be able to configure your existing Rails App to offer a GraphQL API</li>
</ul>
<p><small>Slides - use arrow keys to navigate, esc to return to page view, f for fullscreen</small></p>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-0'>▻</a>
<h2 id="api-styles"><a class="anchorlink" href="#api-styles"><span>1</span> API Styles</a></h2></section>
<section><a class='slide_break' href='graphql-api.html#slide-1'>▻</a>
<h3 id="what-is-an-api-questionmark"><a class="anchorlink" href="#what-is-an-api-questionmark"><span>1.1</span> What is an API?</a></h3><p>API stands for "Application Programming Interface". It is a set of clearly defined methods
of communication with a software component. So the objects and methods exposed by a library
form an API.</p><p>In Web development the acronym API is most
commonly used when the software component in question runs on a different server on the
Internet and is accessed via HTTP.</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-2'>▻</a>
<h3 id="soap-rest-and-graphql"><a class="anchorlink" href="#soap-rest-and-graphql"><span>1.2</span> SOAP, REST and GraphQL</a></h3><p>Currently three main API styles are used on the Web:</p>
<ul>
<li>SOAP, designed 1998 at Microsoft, uses XML and POST requests to make "remote procedure calls"</li>
<li>REST, described in 2000, uses different HTTP Methods and Status Messages to access "resources"</li>
<li>GraphQL, released 2015 by Facebook, uses POST requests, it's own query language and JSON</li>
</ul>
<p>This Guide is concerned with GraphQL, there is a second guide for <a href="/rest-api.html">REST</a>. SOAP
is rearely offered with Rails, but there is a <a href="https://github.com/savonrb/savon">soap client</a> in
ruby.</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-3'>▻</a>
<h3 id="api-layer-is-a-separate-layer"><a class="anchorlink" href="#api-layer-is-a-separate-layer"><span>1.3</span> API layer is a separate layer</a></h3><p>Please note that any of the API styles can be used
with any backend, frontend, persistance layers:</p>
<ul>
<li>You can build a REST in front of a PHP backend using MongoDB as the database and use it from a frontend written with jQuery.</li>
<li>You can build a GraphQL API for a Rails backend using MySQL as the database and build the frontend with React.</li>
</ul>
<p>That's kind of the point of an API: to allow different technologies
on both sides of the API.</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-4'>▻</a>
<h2 id="graphql"><a class="anchorlink" href="#graphql"><span>2</span> GraphQL</a></h2><p>REST and SOAP APIs are fixed interfaces: each api call has a fixed set of
arguments and returns a fixed data structure. All decisions are made when
specifying the API.</p><p>GraphQL shifts some decisions to the client: through a Query Language the client
can request data in the specific shape it needs, within the limits that the
API sets.</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-5'>▻</a>
<h3 id="query-language"><a class="anchorlink" href="#query-language"><span>2.1</span> Query Language</a></h3><p>A simple example with two models: a project has many URLs. when querying
through GraphQL you can request different attributes of both models:</p><p><img src="images/two-queries.gif" alt="1:n relationship in the database"></p><p>Notice how the resulting JSON data mirrors the structure of the query.
The query language is used for both Queries (getting data) and Mutations (changing
data).</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-6'>▻</a>
<h3 id="introspection-and-playground"><a class="anchorlink" href="#introspection-and-playground"><span>2.2</span> Introspection and Playground</a></h3><p>A GraphQL API can always be queried to give information
about the possible queries, mutations and types. This is called
introspection.</p><p>The GraphQL Playground is a Web App that enables you to
make Queries and Mutations. It uses introspection to display
documentation and to offer autocompletion:</p>
<video controls="" autoplay="">
<source src="images/autocomplete.mov" type="video/quicktime">
<source src="images/autocomplete.mp4" type="video/mp4">
</video>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-7'>▻</a>
<h3 id="types"><a class="anchorlink" href="#types"><span>2.3</span> Types</a></h3><p>A GraphQL delivers JSON, which only has objects, arrays, strings, numbers and null
as types. But GraphQL itself can build a more detailed type system and check
these types in queries and mutations.</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-8'>▻</a>
<h3 id="how-the-server-handles-the-request"><a class="anchorlink" href="#how-the-server-handles-the-request"><span>2.4</span> How the server handles the request</a></h3>
<ul>
<li>parse the query</li>
<li>validate with schema</li>
<li>resolve data</li>
<li>convert response to JSON</li>
</ul>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-9'>▻</a>
<h2 id="using-rails-to-build-a-graphql-api"><a class="anchorlink" href="#using-rails-to-build-a-graphql-api"><span>3</span> Using Rails to build a GraphQL API</a></h2></section>
<section><a class='slide_break' href='graphql-api.html#slide-10'>▻</a>
<h3 id="setup"><a class="anchorlink" href="#setup"><span>3.1</span> Setup</a></h3><p>To add a GraphQL API to an existing Rails app you need just two gems:</p><div class="interstitial code">
<pre><code class="highlight plaintext">gem 'graphql'
group :development do
gem 'graphql-rails-generators'
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="gem 'graphql'
group :development do
gem 'graphql-rails-generators'
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-11'>▻</a>
<h4 id="generator"><a class="anchorlink" href="#generator"><span>3.1.1</span> generator</a></h4><p>The rest of the setup is handled by a generator added by the <code>graphql</code> gem:</p><div class="interstitial code">
<pre><code class="highlight plaintext">rails generate graphql:install
exist app/graphql/types
create app/graphql/types/.keep
create app/graphql/portfolio_relaunch_schema.rb
create app/graphql/types/base_object.rb
create app/graphql/types/base_argument.rb
create app/graphql/types/base_field.rb
create app/graphql/types/base_enum.rb
create app/graphql/types/base_input_object.rb
create app/graphql/types/base_interface.rb
create app/graphql/types/base_scalar.rb
create app/graphql/types/base_union.rb
create app/graphql/types/query_type.rb
add_root_type query
create app/graphql/mutations
create app/graphql/mutations/.keep
create app/graphql/mutations/base_mutation.rb
create app/graphql/types/mutation_type.rb
add_root_type mutation
create app/controllers/graphql_controller.rb
route post "/graphql", to: "graphql#execute"
gemfile graphiql-rails
route graphiql-rails
Gemfile has been modified, make sure you `bundle install`
</code></pre>
<button class="clipboard-button" data-clipboard-text="rails generate graphql:install
exist app/graphql/types
create app/graphql/types/.keep
create app/graphql/portfolio_relaunch_schema.rb
create app/graphql/types/base_object.rb
create app/graphql/types/base_argument.rb
create app/graphql/types/base_field.rb
create app/graphql/types/base_enum.rb
create app/graphql/types/base_input_object.rb
create app/graphql/types/base_interface.rb
create app/graphql/types/base_scalar.rb
create app/graphql/types/base_union.rb
create app/graphql/types/query_type.rb
add_root_type query
create app/graphql/mutations
create app/graphql/mutations/.keep
create app/graphql/mutations/base_mutation.rb
create app/graphql/types/mutation_type.rb
add_root_type mutation
create app/controllers/graphql_controller.rb
route post "/graphql", to: "graphql#execute"
gemfile graphiql-rails
route graphiql-rails
Gemfile has been modified, make sure you `bundle install`
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-12'>▻</a>
<h4 id="playground-is-available"><a class="anchorlink" href="#playground-is-available"><span>3.1.2</span> playground is available</a></h4><p>After running bundle and restarting the server you can
access the graphql playground at <code>http://localhost:3000/graphiql</code>:
in the left pane you can enter a query, run it, and see the
result in the middle pane. The right pane contains documentation
that was created automatically.</p><p><img src="images/graphql-playground.png" alt="GraphQL Playground"></p><p>We have no Queries to run yet.</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-13'>▻</a>
<h3 id="generating-a-type-from-a-model"><a class="anchorlink" href="#generating-a-type-from-a-model"><span>3.2</span> Generating a Type from a Model</a></h3><p>As a first step we can
use a generator to create a type from an existing model:</p><div class="interstitial code">
<pre><code class="highlight plaintext">rails generate gql:model_type Project
create app/graphql/types/project_type.rb
</code></pre>
<button class="clipboard-button" data-clipboard-text="rails generate gql:model_type Project
create app/graphql/types/project_type.rb
">Copy</button>
</div>
<p>Now we can edit the type to fit our needs, for example
we can remove attributes that should never be public:</p><div class="interstitial code">
<pre><code class="highlight plaintext">module Types
class ProjectType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: false
field :publicationdate, GraphQL::Types::ISO8601Date, null: false
field :membership, Int, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: false
field :updated_at, GraphQL::Types::ISO8601DateTime, null: false
field :slug, String, null: false
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="module Types
class ProjectType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: false
field :publicationdate, GraphQL::Types::ISO8601Date, null: false
field :membership, Int, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: false
field :updated_at, GraphQL::Types::ISO8601DateTime, null: false
field :slug, String, null: false
end
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-14'>▻</a>
<h3 id="defining-a-query"><a class="anchorlink" href="#defining-a-query"><span>3.3</span> Defining a Query</a></h3><p>The next level up we come to the query. There is already
a dummy Query in <code>app/graphql/types/query_type.rb</code></p><div class="interstitial code">
<pre><code class="highlight plaintext">module Types
class QueryType < Types::BaseObject
# Add root-level fields here.
# They will be entry points for queries on your schema.
# TODO: remove me
field :test_field, String, null: false,
description: "An example field added by the generator"
def test_field
"Hello World!"
end
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="module Types
class QueryType < Types::BaseObject
# Add root-level fields here.
# They will be entry points for queries on your schema.
# TODO: remove me
field :test_field, String, null: false,
description: "An example field added by the generator"
def test_field
"Hello World!"
end
end
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-15'>▻</a>
<h4 id="declare-the-query-and-implement-the-resolver"><a class="anchorlink" href="#declare-the-query-and-implement-the-resolver"><span>3.3.1</span> Declare the Query and implement the resolver</a></h4><p>We can replace this with a query that returns a list of all projects:</p><div class="interstitial code">
<pre><code class="highlight plaintext">module Types
class QueryType < Types::BaseObject
field :all_projects, [ProjectType],
null: false,
description: "a list of all publicly visible projects"
def all_projects
Project.public.all
end
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="module Types
class QueryType < Types::BaseObject
field :all_projects, [ProjectType],
null: false,
description: "a list of all publicly visible projects"
def all_projects
Project.public.all
end
end
end
">Copy</button>
</div>
<p>We can now run the query in the playground. Your query will be autocompleted.</p>
<video controls="" autoplay="">
<source src="images/autocomplete.mov" type="video/quicktime">
<source src="images/autocomplete.mp4" type="video/mp4">
</video>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-16'>▻</a>
<h4 id="queries-with-arguments"><a class="anchorlink" href="#queries-with-arguments"><span>3.3.2</span> Queries with arguments</a></h4><p>If a query needs arguments you have do declare
them in the <code>fields</code> declaration and then handle
them in the method:</p><div class="interstitial code">
<pre><code class="highlight plaintext"> field :project, ProjectType, null: true do
argument :id, ID, required: true
end
def project(id:)
Project.visible.find(id)
end
</code></pre>
<button class="clipboard-button" data-clipboard-text=" field :project, ProjectType, null: true do
argument :id, ID, required: true
end
def project(id:)
Project.visible.find(id)
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-17'>▻</a>
<h3 id="relationships-between-models"><a class="anchorlink" href="#relationships-between-models"><span>3.4</span> Relationships between models</a></h3></section>
<section><a class='slide_break' href='graphql-api.html#slide-18'>▻</a>
<h4 id="create-type-for-a-second-model"><a class="anchorlink" href="#create-type-for-a-second-model"><span>3.4.1</span> Create type for a second model</a></h4><p><img src="images/graphql-project-has-many-urls.png" alt="1:n relationship in the database"></p><p>generate the UrlType automatically from the model:</p><div class="interstitial code">
<pre><code class="highlight plaintext">module Types
class UrlType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: true
field :url, String, null: true
field :url_type, String, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: true
field :updated_at, GraphQL::Types::ISO8601DateTime, null: true
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="module Types
class UrlType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: true
field :url, String, null: true
field :url_type, String, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: true
field :updated_at, GraphQL::Types::ISO8601DateTime, null: true
end
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-19'>▻</a>
<h4 id="create-queries-for-the-second-model"><a class="anchorlink" href="#create-queries-for-the-second-model"><span>3.4.2</span> create queries for the second model</a></h4><p>add the queries <code>all_urls</code> and <code>url</code> to <code>app/graphql/types/query_type.rb</code></p><p>now you can use those queries in the playground</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-20'>▻</a>
<h4 id="add-field-for-relationship-to-type"><a class="anchorlink" href="#add-field-for-relationship-to-type"><span>3.4.3</span> add field for relationship to type</a></h4><p>add the field <code>urls</code> to <code>app/graphql/types/project_type.rb</code>:</p><div class="interstitial code">
<pre><code class="highlight plaintext">module Types
class ProjectType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: false
field :publicationdate, GraphQL::Types::ISO8601Date, null: false
field :membership, Int, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: false
field :updated_at, GraphQL::Types::ISO8601DateTime, null: false
field :slug, String, null: false
field :urls, [ UrlType ], null: false
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="module Types
class ProjectType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: false
field :publicationdate, GraphQL::Types::ISO8601Date, null: false
field :membership, Int, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: false
field :updated_at, GraphQL::Types::ISO8601DateTime, null: false
field :slug, String, null: false
field :urls, [ UrlType ], null: false
end
end
">Copy</button>
</div>
<p>now you can query for Urls through their project:</p><p><img src="images/graphql-query-relationship.png" alt="query a 1:n relationship with graphql"></p></section>
<section><a class='slide_break' href='graphql-api.html#slide-21'>▻</a>
<h4 id="inverse-relationship"><a class="anchorlink" href="#inverse-relationship"><span>3.4.4</span> inverse relationship</a></h4><p>what would you need to do, to make a query
from Url to Project possible?</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
url(id:2077){
id
url
urlType
title
project {
title
}
}
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
url(id:2077){
id
url
urlType
title
project {
title
}
}
}
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-22'>▻</a>
<h4 id="implementation-of-the-inverse-relationship"><a class="anchorlink" href="#implementation-of-the-inverse-relationship"><span>3.4.5</span> implementation of the inverse relationship</a></h4><p>Answer: add a field project to UrlType:</p><div class="interstitial code">
<pre><code class="highlight plaintext">module Types
class UrlType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: true
field :url, String, null: true
field :url_type, String, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: true
field :updated_at, GraphQL::Types::ISO8601DateTime, null: true
field :project, ProjectType, null: false
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="module Types
class UrlType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: true
field :url, String, null: true
field :url_type, String, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: true
field :updated_at, GraphQL::Types::ISO8601DateTime, null: true
field :project, ProjectType, null: false
end
end
">Copy</button>
</div>
<p><img src="images/graphql-query-belongs-to.png" alt="query a 1:n relationship with graphql (reverse)"></p></section>
<section><a class='slide_break' href='graphql-api.html#slide-23'>▻</a>
<h3 id="more-types"><a class="anchorlink" href="#more-types"><span>3.5</span> More Types</a></h3><p>In Ruby and JavaScript we often use Strings to store all
kinds of values. In the example
above, <code>Url.url_type</code> only has three possible values: 'Link','Repository','Award'.</p><p>GraphQL comes with an Enum Type that we can use for that</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-24'>▻</a>
<h4 id="define-the-enum-type"><a class="anchorlink" href="#define-the-enum-type"><span>3.5.1</span> define the Enum Type:</a></h4><div class="interstitial code">
<pre><code class="highlight plaintext">rails g graphql:enum UrlTypeEnum Link Repository Award
create app/graphql/types/url_type_enum_type.rb
</code></pre>
<button class="clipboard-button" data-clipboard-text="rails g graphql:enum UrlTypeEnum Link Repository Award
create app/graphql/types/url_type_enum_type.rb
">Copy</button>
</div>
<div class="interstitial code">
<pre><code class="highlight plaintext">module Types
class UrlTypeEnumType < Types::BaseEnum
value "Link"
value "Repository"
value "Award"
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="module Types
class UrlTypeEnumType < Types::BaseEnum
value "Link"
value "Repository"
value "Award"
end
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-25'>▻</a>
<h4 id="using-the-enum-type"><a class="anchorlink" href="#using-the-enum-type"><span>3.5.2</span> using the Enum Type</a></h4><p>This can now be used in <code>UrlType</code>:</p><div class="interstitial code">
<pre><code class="highlight plaintext">module Types
class UrlType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: true
field :url, String, null: true
field :url_type, UrlTypeEnumType, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: true
field :updated_at, GraphQL::Types::ISO8601DateTime, null: true
field :project, ProjectType, null: false
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="module Types
class UrlType < Types::BaseObject
field :id, GraphQL::Types::ID, null: false
field :title, String, null: true
field :url, String, null: true
field :url_type, UrlTypeEnumType, null: true
field :created_at, GraphQL::Types::ISO8601DateTime, null: true
field :updated_at, GraphQL::Types::ISO8601DateTime, null: true
field :project, ProjectType, null: false
end
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-26'>▻</a>
<h4 id="types-uses-and-limitations"><a class="anchorlink" href="#types-uses-and-limitations"><span>3.5.3</span> Types: uses and limitations</a></h4><p>The data returned by a query is still JSON, and cannot contain
enums, only Strings.</p><p><img src="images/graphql-enum.png" alt="querying an enum gives a string"></p><p>In the documentation you can see that
only three Strings are valid. The GraphQL API will
validate this both in Queries and in Mutations.</p></section>
<section><a class='slide_break' href='graphql-api.html#slide-27'>▻</a>
<h2 id="a-lot-more-to-learn"><a class="anchorlink" href="#a-lot-more-to-learn"><span>4</span> A lot more to learn</a></h2><p>This guide has not touched on:</p>
<ul>
<li>mutations</li>
<li>filtering, searching</li>
<li>pagination</li>
<li>resolving graphql queries that are not directly mapped to models</li>
<li>...</li>
</ul>
</section>
<section><a class='slide_break' href='graphql-api.html#slide-28'>▻</a>
<h3 id="see-also"><a class="anchorlink" href="#see-also"><span>4.1</span> See Also</a></h3>
<ul>
<li><a href="https://www.howtographql.com/graphql-ruby/0-introduction/">GraphQL Guides: Ruby </a></li>
<li><a href="https://pragmaticstudio.com/tutorials/what-is-graphql">Pragmatic Tutorial: GraphQL?</a> (see also part 2 + 3)</li>
<li><a href="https://www.apollographql.com/">Apollo Client + Server</a> in JavaScript</li>
<li><a href="https://api-platform.com/">API Platform</a> to build REST + GraphQL APIs in PHP</li>
<li><a href="https://wundergraph.com/blog/graphql_in_production_analyzing_public_graphql_apis_1_twitch_tv">Analyzing the Twitch.tv GraphQL API</a></li>
</ul>
</div></section>
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