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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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<div class="reveal">
<!-- 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 REST APIs and JSON API</li>
<li>be able to configure your existing controllers to offer resources as JSON</li>
<li>be able to set up an API for your rails app that is separate from existing controllers</li>
</ul>
<div class="interstitial repo"><p>You can study the <a href="https://github.com/backend-development/api_sample_app">code</a> and try out <a href="https://dry-cove-38472.herokuapp.com/">the demo</a> for the example described here.</p></div>
<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='apis.html#slide-0'>▻</a>
<h2 id="what-is-an-api"><a class="anchorlink" href="#what-is-an-api"><span>1</span> What is an API</a></h2><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 the network.</p><p>This Guide is concerned with APIs that you build and run using Ruby on Rails.</p></section>
<section><a class='slide_break' href='apis.html#slide-1'>▻</a>
<h2 id="rest"><a class="anchorlink" href="#rest"><span>2</span> REST</a></h2><p>The acronym REST was coined by Roy Fielding in his dissertation. When describing
the architecture of the web, and what made it so successfull on a technical level,
he desribed this architecture as "Representational State Transfer" (REST).</p><p>This Acronym was later picked up to describe a certain style of API,
and to distiguish such APIs from SOAP APIs.</p><p>A REST API allows to access and manipulate textual representations of Web resources using HTTP Methods and stateless operations.</p><p>"Web resources" were first defined on the World Wide Web as documents or files identified by their URLs, but today they have a much more generic and abstract definition encompassing every thing or entity that can be identified, named, addressed or handled, in any way whatsoever, on the Web.</p><p><a href="https://www.infoq.com/articles/rest-introduction">Tilkov(2007)</a> gives a brief introduction to REST. The main points are:</p>
<ol>
<li> Give every resource a unique URL</li>
<li> “Hypermedia as the engine of application state” (HATEOAS) - use URLs to reference other resources (not just ids)</li>
<li> Use HTTP Methods (and Status Codes) as intended.</li>
<li> One resource can have multiple representations, for example HTML, JSON and XML</li>
<li> Communicate statelessly - if possible!</li>
</ol>
</section>
<section><a class='slide_break' href='apis.html#slide-2'>▻</a>
<h3 id="exploring-a-rest-api-with-postman"><a class="anchorlink" href="#exploring-a-rest-api-with-postman"><span>2.1</span> Exploring a REST API with postman</a></h3><p>TODO</p></section>
<section><a class='slide_break' href='apis.html#slide-3'>▻</a>
<h3 id="urls"><a class="anchorlink" href="#urls"><span>2.2</span> URLS</a></h3><p>Give every resource a unique URL.
Please note that REST does not demand a certain form of URL.
While URLs with no parameters are often used:</p><div class="interstitial code">
<pre><code class="highlight plaintext">https://example.com/users/
https://example.com/users/1/
https://example.com/users/2/
https://example.com/users/3/
</code></pre>
<button class="clipboard-button" data-clipboard-text="https://example.com/users/
https://example.com/users/1/
https://example.com/users/2/
https://example.com/users/3/
">Copy</button>
</div>
<p>it is just as restful to use parameters:</p><div class="interstitial code">
<pre><code class="highlight plaintext">https://example.com/users.php
https://example.com/users.php?id=1
https://example.com/users.php?id=2
https://example.com/users.php?id=3
</code></pre>
<button class="clipboard-button" data-clipboard-text="https://example.com/users.php
https://example.com/users.php?id=1
https://example.com/users.php?id=2
https://example.com/users.php?id=3
">Copy</button>
</div>
<p>In REST, the URLs correspond to resources, which are represented by nouns.
This is a difference to SOAP, there there is typically just one endpoint:</p><div class="interstitial code">
<pre><code class="highlight plaintext">https://example.com/soap/router/
</code></pre>
<button class="clipboard-button" data-clipboard-text="https://example.com/soap/router/
">Copy</button>
</div>
<p>Through this endpoint you can access methods like <code>getUserData()</code> or <code>deleteUser()</code>.</p></section>
<section><a class='slide_break' href='apis.html#slide-4'>▻</a>
<h3 id="hateoas"><a class="anchorlink" href="#hateoas"><span>2.3</span> HATEOAS</a></h3><p>“Hypermedia as the engine of application state” means that a client interacts with a network application entirely through hypermedia, and needs no prior knowledge of URLs.</p><p>If an API returns the following JSON:</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
"id": "1",
"name": "Example User",
"email": "example@railstutorial.org"
"profile_pics": [ 2, 5 ]
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
"id": "1",
"name": "Example User",
"email": "example@railstutorial.org"
"profile_pics": [ 2, 5 ]
}
">Copy</button>
</div>
<p>Then the Client needs to know how to get profile_pics from the API.
For example because the developer read the docs.</p><p>HATEOAS demands that the full URL is used to refer to other resources:</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
"id": "1",
"name": "Example User",
"email": "example@railstutorial.org"
"profile_pics": [
"https://sample.com/api/profile/pictures/2",
"https://sample.com/api/profile/pictures/5"
]
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
"id": "1",
"name": "Example User",
"email": "example@railstutorial.org"
"profile_pics": [
"https://sample.com/api/profile/pictures/2",
"https://sample.com/api/profile/pictures/5"
]
}
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='apis.html#slide-5'>▻</a>
<h3 id="http-methods-and-status-codes"><a class="anchorlink" href="#http-methods-and-status-codes"><span>2.4</span> HTTP Methods and Status Codes</a></h3><p>Use HTTP Methods (and Status Codes) as intended.</p><p>Regarding the HTTP Methods there are two important distinctions:</p>
<ul>
<li>the GET and HEAD methods should take no other action than retrieval. These methods ought to be considered <strong>safe</strong>.</li>
<li>The methods GET, HEAD, PUT and DELETE are idempotent: repeating the request will not change the end result (aside from error or expiration issues)</li>
</ul>
<p>The definition of the <a href="https://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html">Methods</a> in HTTP1.0 is just a short read, and worth its while!</p><p>References for status codes:</p>
<ul>
<li><a href="https://httpstatuses.com/422">Status codes</a></li>
<li><a href="https://http.cat/">Status cats</a></li>
</ul>
<p>When buidling a REST API, the HTTP Protocol already defines a lot
about that API. There is no need to come up with a way to delete
a resource, or to indicate failure. HTTP already offers the DELETE method
and status codes that indicate errors.</p></section>
<section><a class='slide_break' href='apis.html#slide-6'>▻</a>
<h3 id="multiple-representations"><a class="anchorlink" href="#multiple-representations"><span>2.5</span> Multiple Representations</a></h3><p>The same resource can be available in different formats.
There are two common ways of requesting different formats:</p><p>With the HTTP Header <code>Accept</code>:</p><div class="interstitial code">
<pre><code class="highlight plaintext">GET /mini/person/83 HTTP/1.1
Host: example.com
Accept: application/xml
</code></pre>
<button class="clipboard-button" data-clipboard-text="GET /mini/person/83 HTTP/1.1
Host: example.com
Accept: application/xml
">Copy</button>
</div>
<p>Or by adding an "extension" as part of the URL:</p><div class="interstitial code">
<pre><code class="highlight plaintext">https://example.com/mini/person/83.html
https://example.com/mini/person/83.xml
https://example.com/mini/person/83.json
</code></pre>
<button class="clipboard-button" data-clipboard-text="https://example.com/mini/person/83.html
https://example.com/mini/person/83.xml
https://example.com/mini/person/83.json
">Copy</button>
</div>
<p>The three different versions of person number 83 might look
like this: the HTML web page:</p><div class="interstitial code">
<pre><code class="highlight plaintext"><h1>Details zu einer Person</h1>
<p><img src="https://example.com/mini/profil/edvard_1_2.jpg" />
Herr Edvard Paul Beisteiner hat insgesamt 4 Werke in dieser Datenbank.
Er hat den Usernamen fhs14287.</p>
<ul>
<li><a href='https://example.com/mini/werk/24'>The Thin Red Line</a></li>
<li><a href='https://example.com/mini/werk/50'>Der böse Wolf</a></li>
<li><a href='https://example.com/mini/werk/83'>nimm zwei, schatz</a></li>
<li><a href='https://example.com/mini/werk/303'>the neighbour.</a></li>
</ul>
</code></pre>
<button class="clipboard-button" data-clipboard-text="<h1>Details zu einer Person</h1>
<p><img src="https://example.com/mini/profil/edvard_1_2.jpg" />
Herr Edvard Paul Beisteiner hat insgesamt 4 Werke in dieser Datenbank.
Er hat den Usernamen fhs14287.</p>
<ul>
<li><a href='https://example.com/mini/werk/24'>The Thin Red Line</a></li>
<li><a href='https://example.com/mini/werk/50'>Der böse Wolf</a></li>
<li><a href='https://example.com/mini/werk/83'>nimm zwei, schatz</a></li>
<li><a href='https://example.com/mini/werk/303'>the neighbour.</a></li>
</ul>
">Copy</button>
</div>
<p>For an API the same resource might be represented as XML:</p><div class="interstitial code">
<pre><code class="highlight plaintext"><person>
<image ref='https://example.com/mini/profil/edvard_1_2.jpg' />
<vorname>Edvard</vorname>
<nachname>Beisteiner</nachname>
<username>fhs14287</username>
<werke>
<werk ref='https://example.com/mini/werk/24'>The Thin Red Line</werk>
<werk ref='https://example.com/mini/werk/50'>Der böse Wolf</werk>
<werk ref='https://example.com/mini/werk/83'>nimm zwei, schatz</werk>
<werk ref='https://example.com/mini/werk/303'>the neighbour.</werk>
</werke>
</person>
</code></pre>
<button class="clipboard-button" data-clipboard-text="<person>
<image ref='https://example.com/mini/profil/edvard_1_2.jpg' />
<vorname>Edvard</vorname>
<nachname>Beisteiner</nachname>
<username>fhs14287</username>
<werke>
<werk ref='https://example.com/mini/werk/24'>The Thin Red Line</werk>
<werk ref='https://example.com/mini/werk/50'>Der böse Wolf</werk>
<werk ref='https://example.com/mini/werk/83'>nimm zwei, schatz</werk>
<werk ref='https://example.com/mini/werk/303'>the neighbour.</werk>
</werke>
</person>
">Copy</button>
</div>
<p>or as JSON:</p><div class="interstitial code">
<pre><code class="highlight plaintext">{"image":"https://example.com/mini/profil/edvard_1_2.jpg",
"vorname":"Eduard",
"nachname":"Beisteiner",
"werk":[
{"titel":"The Thin Red Line",
"url":"https://example.com/mini/werk/24"},
{"titel":"Der böse Wolf",
"url":"https://example.com/mini/werk/50"},
{"titel":"nimm zwei, schatz",
"url":"https://example.com/mini/werk/83"},
{"titel":"the neighbour.",
"url":"https://example.com/mini/werk/303"}]}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{"image":"https://example.com/mini/profil/edvard_1_2.jpg",
"vorname":"Eduard",
"nachname":"Beisteiner",
"werk":[
{"titel":"The Thin Red Line",
"url":"https://example.com/mini/werk/24"},
{"titel":"Der böse Wolf",
"url":"https://example.com/mini/werk/50"},
{"titel":"nimm zwei, schatz",
"url":"https://example.com/mini/werk/83"},
{"titel":"the neighbour.",
"url":"https://example.com/mini/werk/303"}]}
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='apis.html#slide-7'>▻</a>
<h3 id="statelessness"><a class="anchorlink" href="#statelessness"><span>2.6</span> Statelessness</a></h3><p>Tilkov wirtes: "REST mandates that state be either turned into resource state, or kept on the client. In other words, a server should not have to retain some sort of communication state for any of the clients it communicates with beyond a single request."</p><p>This is important for performance and scalability and performance.
Statelessness makes caching easy. And in a scenario with serveral
servers behind a load balancer, not having state on the server means
the application will work if the requests bei one client are routest
to different servers.</p></section>
<section><a class='slide_break' href='apis.html#slide-8'>▻</a>
<h3 id="json-api"><a class="anchorlink" href="#json-api"><span>2.7</span> JSON API</a></h3><p>When an API returns JSON data this could take many forms.
The <a href="https://jsonapi.org/">json:api specification</a> is a well thought out
convention for this.</p><p>It is especially good with the HATEOS aspect of REST, the json:api specification adhers to this principle.</p></section>
<section><a class='slide_break' href='apis.html#slide-9'>▻</a>
<h2 id="graphql"><a class="anchorlink" href="#graphql"><span>3</span> GraphQL</a></h2><p>GraphQL is different way of writing APIs. GraphQL is less
concerned with HTTP, it just uses the POST method for all requests.</p><p>see</p>
<ul>
<li><a href="https://rmosolgo.github.io/talks">author of graphql gem</a></li>
<li><a href="https://www.howtographql.com">howtographql</a></li>
<li><a href="https://graphql.org">graphql</a></li>
</ul>
</section>
<section><a class='slide_break' href='apis.html#slide-10'>▻</a>
<h3 id="exploring-graphql-with-playground"><a class="anchorlink" href="#exploring-graphql-with-playground"><span>3.1</span> exploring GraphQL with Playground</a></h3><p>GraphQL Playground</p></section>
<section><a class='slide_break' href='apis.html#slide-11'>▻</a>
<h3 id="types"><a class="anchorlink" href="#types"><span>3.2</span> types</a></h3></section>
<section><a class='slide_break' href='apis.html#slide-12'>▻</a>
<h3 id="basic-example"><a class="anchorlink" href="#basic-example"><span>3.3</span> basic example</a></h3><p>example query:</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
cityZone(id: "2349ksj0342" ) {
id
url
}
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
cityZone(id: "2349ksj0342" ) {
id
url
}
}
">Copy</button>
</div>
<p>a possible resonse</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
"data": {
"cityZone": {
"id": "2349ksj0342",
"url": "wuppertal"
}
}
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
"data": {
"cityZone": {
"id": "2349ksj0342",
"url": "wuppertal"
}
}
}
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='apis.html#slide-13'>▻</a>
<h3 id="how-the-server-handles-the-request"><a class="anchorlink" href="#how-the-server-handles-the-request"><span>3.4</span> how the server handles the request</a></h3>
<ul>
<li>parse 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='apis.html#slide-14'>▻</a>
<h3 id="aggragate"><a class="anchorlink" href="#aggragate"><span>3.5</span> aggragate</a></h3></section>
<section><a class='slide_break' href='apis.html#slide-15'>▻</a>
<h3 id="pagination"><a class="anchorlink" href="#pagination"><span>3.6</span> pagination</a></h3></section>
<section><a class='slide_break' href='apis.html#slide-16'>▻</a>
<h3 id="mutation-and-response"><a class="anchorlink" href="#mutation-and-response"><span>3.7</span> mutation and response</a></h3></section>
<section><a class='slide_break' href='apis.html#slide-17'>▻</a>
<h3 id="errors"><a class="anchorlink" href="#errors"><span>3.8</span> errors</a></h3></section>
<section><a class='slide_break' href='apis.html#slide-18'>▻</a>
<h3 id="versioning-deprecation"><a class="anchorlink" href="#versioning-deprecation"><span>3.9</span> versioning, deprecation</a></h3></section>
<section><a class='slide_break' href='apis.html#slide-19'>▻</a>
<h2 id="using-rails-to-build-a-basic-rest-api"><a class="anchorlink" href="#using-rails-to-build-a-basic-rest-api"><span>4</span> Using Rails to build a basic REST API</a></h2><p>Rails is equipped to not just create HTML as output, but to easily
offer other representations as well.</p><p>When you look at <code>rails routes</code> you can see that the routes created by
<code>resource :user</code> could contain an optional <code>format</code>:</p><div class="interstitial code">
<pre><code class="highlight plaintext"> Prefix Verb URI Pattern Controller#Action
root GET / static_pages#home
users GET /users(.:format) users#index
user GET /users/:id(.:format) users#show
</code></pre>
<button class="clipboard-button" data-clipboard-text=" Prefix Verb URI Pattern Controller#Action
root GET / static_pages#home
users GET /users(.:format) users#index
user GET /users/:id(.:format) users#show
">Copy</button>
</div>
<p>Only HTML is implemented by default. But we could use this feature
to have other formats:</p>
<ul>
<li><code>/users</code></li>
<li><code>/users.json</code></li>
<li><code>/users.xml</code></li>
<li><code>/users/1</code></li>
<li><code>/users/1.json</code></li>
<li><code>/users/1.xml</code></li>
</ul>
<p>When you try out accessing <code>/users/1.json</code> you get a response:</p><div class="interstitial code">
<pre><code class="highlight plaintext">406 Not Acceptable
Content-Length: 39
Content-Type: application/json; charset=utf-8
{"status":406,"error":"Not Acceptable"}
</code></pre>
<button class="clipboard-button" data-clipboard-text="406 Not Acceptable
Content-Length: 39
Content-Type: application/json; charset=utf-8
{"status":406,"error":"Not Acceptable"}
">Copy</button>
</div>
<p>This error message is meant for a
client expecting JSON data. It uses both the HTTP status code
and the JSON to indicate the error.</p></section>
<section><a class='slide_break' href='apis.html#slide-20'>▻</a>
<h3 id="api-for-the-sample-app"><a class="anchorlink" href="#api-for-the-sample-app"><span>4.1</span> API for the sample app</a></h3><p>The "Frontend 1" in the example app expects a very simple JSON structure:</p><p>To display one user, it loads from <code>/user/1.json</code> and expects
a single JSON object with three attributes:</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
"id":1,
"name":"Example User",
"email":"example@railstutorial.org"
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
"id":1,
"name":"Example User",
"email":"example@railstutorial.org"
}
">Copy</button>
</div>
<p>To display the table of users, it loads from <code>/users.json</code> and
expects a JSON array of objects like above:</p><div class="interstitial code">
<pre><code class="highlight plaintext">[
{
"id":2,
"name":"Precious Heaney",
"email":"example-1@railstutorial.org"
},
{
"id":3,
"name":"Warren Considine Sr.",
"email":"example-2@railstutorial.org"
}
]
</code></pre>
<button class="clipboard-button" data-clipboard-text="[
{
"id":2,
"name":"Precious Heaney",
"email":"example-1@railstutorial.org"
},
{
"id":3,
"name":"Warren Considine Sr.",
"email":"example-2@railstutorial.org"
}
]
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='apis.html#slide-21'>▻</a>
<h3 id="creating-an-api-with-existing-controllers"><a class="anchorlink" href="#creating-an-api-with-existing-controllers"><span>4.2</span> creating an API with existing controllers</a></h3><p>The scaffold generator always adds handling JSON responses
to the actions of a controller.</p><p>For handling just HTML only this code would be needed in the
create action:</p><div class="interstitial code">
<pre><code class="highlight plaintext"> # POST /users
def create
@user = User.new(user_params)
if @user.save
redirect_to @user, notice: 'User was successfully created.'
else
render :new
end
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text=" # POST /users
def create
@user = User.new(user_params)
if @user.save
redirect_to @user, notice: 'User was successfully created.'
else
render :new
end
end
end
">Copy</button>
</div>
<p>But the scaffold generator also adds <code>resond_to</code> and <code>format</code> commands,
to handle json differently from html:</p><div class="interstitial code">
<pre><code class="highlight plaintext"> # POST /users
# POST /users.json
def create
@user = User.new(user_params)
respond_to do |format|
if @user.save
format.html {
redirect_to @user, notice: 'User was successfully created.'
}
format.json {
render :show, status: :created, location: @user
}
else
format.html {
render :new
}
format.json {
render json: @user.errors, status: :unprocessable_entity
}
end
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text=" # POST /users
# POST /users.json
def create
@user = User.new(user_params)
respond_to do |format|
if @user.save
format.html {
redirect_to @user, notice: 'User was successfully created.'
}
format.json {
render :show, status: :created, location: @user
}
else
format.html {
render :new
}
format.json {
render json: @user.errors, status: :unprocessable_entity
}
end
end
end
">Copy</button>
</div>
<p>so in the controller we might not need to change anything to add the
API, only in the view.</p></section>
<section><a class='slide_break' href='apis.html#slide-22'>▻</a>
<h3 id="creating-json-with-erb-not-a-good-idea"><a class="anchorlink" href="#creating-json-with-erb-not-a-good-idea"><span>4.3</span> creating JSON with erb - not a good idea</a></h3><p>We could create views using erb in <code>app/views/users/show.json.erb</code>:</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
"id": <%= @user.id %>,
"name": "<%= @user.name %>",
"email": "<%= @user.email %>"
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
"id": <%= @user.id %>,
"name": "<%= @user.name %>",
"email": "<%= @user.email %>"
}
">Copy</button>
</div>
<p>and <code>app/views/users/index.json.erb</code>:</p><div class="interstitial code">
<pre><code class="highlight plaintext">[
<%
@users.each_with_index do |user| %>
{
"id": <%= user.id %>,
"name": "<%= user.name %>",
"email": "<%= user.email %>"
},
<% end %>
]
</code></pre>
<button class="clipboard-button" data-clipboard-text="[
<%
@users.each_with_index do |user| %>
{
"id": <%= user.id %>,
"name": "<%= user.name %>",
"email": "<%= user.email %>"
},
<% end %>
]
">Copy</button>
</div>
<p>But wait, there's a problem: there is a comma after each object,
but there should be no comma after the last.</p><div class="interstitial code">
<pre><code class="highlight plaintext">[
<%
max = @users.length - 1
@users.each_with_index do |user,i| %>
{
"id": <%= user.id %>,
"name": "<%= user.name %>",
"email": "<%= user.email %>"
}
<%= if i < max then ',' end %>
<% end %>
]
</code></pre>
<button class="clipboard-button" data-clipboard-text="[
<%
max = @users.length - 1
@users.each_with_index do |user,i| %>
{
"id": <%= user.id %>,
"name": "<%= user.name %>",
"email": "<%= user.email %>"
}
<%= if i < max then ',' end %>
<% end %>
]
">Copy</button>
</div>
<p>And wait, there's another problem: What happens
if a users name contains a quote? For example <kbd>Jack "the Ripper"</kbd>.
That would break our current view, because we don't do proper escaping.</p></section>
<section><a class='slide_break' href='apis.html#slide-23'>▻</a>
<h3 id="creating-json-with-jbuilder-a-better-idea"><a class="anchorlink" href="#creating-json-with-jbuilder-a-better-idea"><span>4.4</span> creating JSON with jbuilder - a better idea</a></h3><p>Rails 5 comes with the gem <code>jbuilder</code> which helps you create JSON, and
which handles all the escaping and formatting correctly.</p><p>We need to name the view <code>app/views/users/show.json.jbuilder</code>,
and then can use the the following code to extract three properties
from the user object:</p><div class="interstitial code">
<pre><code class="highlight plaintext">json.id @user.id
json.name @user.name
json.email @user.email
</code></pre>
<button class="clipboard-button" data-clipboard-text="json.id @user.id
json.name @user.name
json.email @user.email
">Copy</button>
</div>
<p>There is also a shorthand for this:</p><div class="interstitial code">
<pre><code class="highlight plaintext">json.extract! @user, :id, :name, :email
</code></pre>
<button class="clipboard-button" data-clipboard-text="json.extract! @user, :id, :name, :email
">Copy</button>
</div>
<p>For the index view we want to create a JSON array.
In <code>app/views/users/index.json.jbuilder</code> we write:</p><div class="interstitial code">
<pre><code class="highlight plaintext">json.array! @users do |user|
json.extract! user, :id, :name, :email
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="json.array! @users do |user|
json.extract! user, :id, :name, :email
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='apis.html#slide-24'>▻</a>
<h3 id="authentication-and-the-api"><a class="anchorlink" href="#authentication-and-the-api"><span>4.5</span> Authentication and the API</a></h3><p>All the authentication and access control we built into the
rails app before is still applicable to the API and JSON views.
If the "Frontend" that is using our API is displayed in a browser,
the handling of cookies and the session is exactly the same as before.</p><p>If the "Frontend" is not in a browser, but is a native mobile app or
just another server side job, we have to use an alternative to cookies.
<a href="https://backend-development.github.io/rails_authentication.html#how-to-add-state-to-http">JSON Web Tokens</a> are a solution.</p></section>
<section><a class='slide_break' href='apis.html#slide-25'>▻</a>
<h2 id="using-rails-to-build-a-stand-alone-rest-api"><a class="anchorlink" href="#using-rails-to-build-a-stand-alone-rest-api"><span>5</span> Using Rails to build a stand alone REST API</a></h2><p>To create a stand alone API we define new, separate routes under <code>/api/v1</code>.</p><div class="interstitial code">
<pre><code class="highlight plaintext">namespace :api do
namespace :v1 do
resources :users, only: [:index, :create, :show, :update, :destroy]
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="namespace :api do
namespace :v1 do
resources :users, only: [:index, :create, :show, :update, :destroy]
end
end
">Copy</button>
</div>
<p>we will be using the <code>fast_jsonapi</code> gem for creating JSON output that compllies to jsonapi:</p><div class="interstitial code">
<pre><code class="highlight plaintext">bundle add 'fast_jsonapi'
</code></pre>
<button class="clipboard-button" data-clipboard-text="bundle add 'fast_jsonapi'
">Copy</button>
</div>
<p><strong>Beware</strong>: After adding a gem you
need to restart the rails server!</p></section>
<section><a class='slide_break' href='apis.html#slide-26'>▻</a>
<h3 id="jsonapi-for-the-sample-app"><a class="anchorlink" href="#jsonapi-for-the-sample-app"><span>5.1</span> JSONAPI for the sample app</a></h3><p>The "Frontend 2" in the example app expects the json to be formed
according to the json api specification.</p><p><code>/api/v1/user/1</code> will return data about one resource:</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
"data": {
"id": "1",
"type": "users",
"attributes": {
"name": "Example User",
"email": "example@railstutorial.org"
}
}
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
"data": {
"id": "1",
"type": "users",
"attributes": {
"name": "Example User",
"email": "example@railstutorial.org"
}
}
}
">Copy</button>
</div>
<p><code>/api/v1/users/</code> returns an array, but the top level JSON structure
is an object with on attribute <code>data</code>:</p><div class="interstitial code">
<pre><code class="highlight plaintext">{
"data": [
{
"id": "2",
"type": "users",
"attributes": {
"name": "Precious Heaney",
"email": "example-1@railstutorial.org"
},
},
...
]
}
</code></pre>
<button class="clipboard-button" data-clipboard-text="{
"data": [
{
"id": "2",
"type": "users",
"attributes": {
"name": "Precious Heaney",
"email": "example-1@railstutorial.org"
},
},
...
]
}
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='apis.html#slide-27'>▻</a>
<h3 id="creating-json-with-fast-jsonapi"><a class="anchorlink" href="#creating-json-with-fast-jsonapi"><span>5.2</span> creating JSON with fast_jsonapi</a></h3><p>After we defined the routes, we next need to create a controller.
As we are setting up a new hierarchy of controllers that will only
concerned with the API, it makes sense to inhert from <code>ActionController::API</code>,
not from <code>ActionController::Base</code>.</p><p>All the "normal" controllers first inhert from <code>ApplicationController</code>. We
will build a similar structure for the api controllers, the will inhert from
<code>Api::V1::BaseController</code>:</p><div class="interstitial code">
<pre><code class="highlight plaintext"># app/controllers/api/v1/base_controller.rb
class Api::V1::BaseController < ActionController::API
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="# app/controllers/api/v1/base_controller.rb
class Api::V1::BaseController < ActionController::API
end
">Copy</button>
</div>
<p>The users controller is the one that's actually called by the route:</p><div class="interstitial code">
<pre><code class="highlight plaintext"># app/controllers/api/v1/users_controller.rb
class Api::V1::UsersController < Api::V1::BaseController
def index
users = User.all
render json: UserSerializer.new(users).serialized_json
end
def show
user = User.find(params[:id])
render json: UserSerializer.new(user).serialized_json
end
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="# app/controllers/api/v1/users_controller.rb
class Api::V1::UsersController < Api::V1::BaseController
def index
users = User.all
render json: UserSerializer.new(users).serialized_json
end
def show
user = User.find(params[:id])
render json: UserSerializer.new(user).serialized_json
end
end
">Copy</button>
</div>
<p>The controller loads the right model, and then calls a <strong>serializer</strong> to
do the actual rendering of the json data.</p><p>All serializers live in the <code>/app/serializers</code> folder.
You can generate a serializer from an existing model:</p><div class="interstitial code">
<pre><code class="highlight plaintext">rails g serializer User name email
</code></pre>
<button class="clipboard-button" data-clipboard-text="rails g serializer User name email
">Copy</button>
</div>
<p>this creates the following code:</p><div class="interstitial code">
<pre><code class="highlight plaintext"># app/serializers/user_serializer.rb
class UserSerializer
include FastJsonapi::ObjectSerializer
attributes :name, :email
end
</code></pre>
<button class="clipboard-button" data-clipboard-text="# app/serializers/user_serializer.rb
class UserSerializer
include FastJsonapi::ObjectSerializer
attributes :name, :email
end
">Copy</button>
</div>
</section>
<section><a class='slide_break' href='apis.html#slide-28'>▻</a>
<h2 id="using-rails-to-build-a-graphql-api"><a class="anchorlink" href="#using-rails-to-build-a-graphql-api"><span>6</span> Using Rails to build a GraphQL API</a></h2>
<ul>
<li>Hannes sagt gem graphql, für n+1 queries graphql-batch von shopify. und graphiql</li>
<li><a href="https://github.com/eliias/concat-tv">https://github.com/eliias/concat-tv</a></li>
<li><a href="https://www.howtographql.com/graphql-ruby/0-introduction/">https://www.howtographql.com/graphql-ruby/0-introduction/</a></li>
<li><a href="https://github.com/ajsharp/graphql-rails-generators">https://github.com/ajsharp/graphql-rails-generators</a></li>
</ul>
</section>
<section><a class='slide_break' href='apis.html#slide-29'>▻</a>
<h2 id="documenting-an-api"><a class="anchorlink" href="#documenting-an-api"><span>7</span> Documenting an API</a></h2><p>See Halliday(2016): <a href="https://blog.codeship.com/producing-documentation-for-your-rails-api/">Producing Documentation for Your Rails API</a> for a discussion of automatic methods of documentation generation.</p></section>
<section><a class='slide_break' href='apis.html#slide-30'>▻</a>
<h2 id="see-also"><a class="anchorlink" href="#see-also"><span>8</span> See Also</a></h2>
<ul>
<li><a href="https://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm">Fielding, Roy(2000): Architectural Styles and the Design of Network-based Software Architectures</a>. Dissertation. University of California/Irvine, USA.</li>
<li><a href="https://martinfowler.com/articles/richardsonMaturityModel.html">Fowler (2010): Richardson Maturity Model</a></li>
<li><a href="https://www.infoq.com/articles/rest-introduction">Tilkov(2007): A Brief Introduction to REST</a></li>
<li><a href="http://standards.rest/">standards.rest</a> a collection of standards that have developed around REST</li>
<li><a href="https://edgeguides.rubyonrails.org/action_controller_overview.html#rendering-xml-and-json-data">Rails Guide: Rendering JSON in Action Controller Overview</a></li>
<li><a href="https://edgeguides.rubyonrails.org/api_app.html">Rails Guide: Using Rails for API-only Applications</a></li>
<li><a href="https://github.com/vasilakisfil/rails5_api_tutorial">Vasilakis(2017): Rails 5 API Tutorial</a></li>
<li><a href="https://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html">Methods HTTP/1.0</a></li>
<li><a href="https://httpstatuses.com/422">Status codes</a></li>
<li><a href="https://github.com/nsarno/knock">gem knock</a> for token based authentication for API only Rails apps</li>
</ul>
</div></section>
</div>
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