V2.1: Building an API
Now that we’ve created our app, let’s turn it into an API.
Adding our first functionality
Let’s take a look at Hanami by creating the beginnings of a bookshelf app.
In the file spec/requests/root_spec.rb, Hanami provides a request spec for the “Hello from Hanami” message we’ve seen in the browser.
# spec/requests/root_spec.rb
RSpec.describe "Root", type: :request do
it "is successful" do
get "/"
# Find me in `config/routes.rb`
expect(last_response).to be_successful
expect(last_response.body).to eq("Hello from Hanami")
end
end
We can run that spec now to prove that it works:
$ bundle exec rspec spec/requests/root_spec.rb
You should see:
Root
is successful
Finished in 0.01986 seconds (files took 0.70103 seconds to load)
1 example, 0 failures
Let’s change the “Hello from Hanami” message to “Welcome to Bookshelf”. First, we’ll adjust our spec:
# spec/requests/root_spec.rb
RSpec.describe "Root", type: :request do
it "is successful" do
get "/"
# Find me in `config/routes.rb`
expect(last_response).to be_successful
expect(last_response.body).to eq("Welcome to Bookshelf")
end
end
As we expect, when we run the spec again, it fails:
$ bundle exec rspec spec/requests/root_spec.rb
Root
is successful (FAILED - 1)
Failures:
1) Root is successful
Failure/Error: expect(last_response.body).to eq("Welcome to Bookshelf")
expected: "Welcome to Bookshelf"
got: "Hello from Hanami"
(compared using ==)
# ./spec/requests/root_spec.rb:9:in `block (2 levels) in <top (required)>'
Finished in 0.04572 seconds (files took 0.72148 seconds to load)
1 example, 1 failure
To fix this, let’s open our app’s routes file at config/routes.rb:
# config/routes.rb
module Bookshelf
class Routes < Hanami::Routes
root { "Hello from Hanami" }
end
end
This Bookshelf::Routes class contains the configuration for our app’s router. Routes in Hanami are comprised of a HTTP method, a path, and an endpoint to be invoked, which is usually a Hanami action. (See the Routing guide for more information).
We’ll take a look at adding more routes in a moment, but for now let’s get our spec to pass. The above Bookshelf::Routes class contains only one route, the root route, which handles GET requests for "/".
Rather than invoking an action, this route is configured to invoke a block, which returns “Hello from Hanami”.
Blocks are convenient, but let’s adjust our route to invoke an action instead:
# config/routes.rb
module Bookshelf
class Routes < Hanami::Routes
root to: "home.show"
end
end
If we run our test again, we’ll see a Hanami::Routes::MissingActionError:
$ bundle exec rspec spec/requests/root_spec.rb
Failures:
1) Root is successful
Failure/Error: get "/"
Hanami::Routes::MissingActionError:
Could not find action with key "actions.home.show" in Bookshelf::App
To fix this, define the action class Bookshelf::Actions::Home::Show in app/actions/home/show.rb
# ./spec/requests/root_spec.rb:5:in `block (2 levels) in <top (required)>'
Finished in 0.01871 seconds (files took 0.62516 seconds to load)
1 example, 1 failure
As this error suggests, we need to create the home show action the route is expecting to be able to call.
Hanami provides an action generator we can use to create this action. Running this command will create the home show action:
$ bundle exec hanami generate action home.show --skip-view
We can find this action in our app directory at app/actions/home/show.rb:
# app/actions/home/show.rb
module Bookshelf
module Actions
module Home
class Show < Bookshelf::Action
def handle(*, response)
response.body = self.class.name
end
end
end
end
end
In a Hanami app, every action is an individual class. Actions decide what HTTP response (body, headers and status code) to return for a given request.
Actions define a #handle method which accepts a request object, representing the incoming request, and a response object, representing the outgoing response.
def handle(request, response)
# ...
end
In the automatically generated home show action above, * is used for the request argument because the action does not currently use the request.
For more details on actions, see the Actions guide.
For now, let’s adjust our home action to return our desired “Welcome to Bookshelf” message.
# app/actions/home/show.rb
module Bookshelf
module Actions
module Home
class Show < Bookshelf::Action
def handle(*, response)
response.body = "Welcome to Bookshelf"
end
end
end
end
end
With this change, our root spec will now pass:
$ bundle exec rspec spec/requests/root_spec.rb
Root
is successful
Finished in 0.03029 seconds (files took 0.72932 seconds to load)
1 example, 0 failures
Adding a new route and action
As the next step in our bookshelf project, let’s add the ability to display an index of all books in the system, delivered as a JSON API.
First we’ll create a request spec for listing books that expects a successful JSON formatted response, listing two books:
# spec/requests/books/index_spec.rb
RSpec.describe "GET /books", type: :request do
it "returns a list of books" do
get "/books"
expect(last_response).to be_successful
expect(last_response.content_type).to eq("app/json; charset=utf-8")
response_body = JSON.parse(last_response.body)
expect(response_body).to eq([
{ "title" => "Test Driven Development" },
{ "title" => "Practical Object-Oriented Design in Ruby" }
])
end
end
If you run this test, you’ll see that it fails because our app currently returns a 404 response for the /books route.
Let’s fix that by generating an action for a books index:
$ bundle exec hanami generate action books.index --skip-view
In addition to generating an action at app/actions/books/index.rb, the generator has also added a route in config/routes.rb:
module Bookshelf
class Routes < Hanami::Routes
root to: "home.index"
get "/books", to: "books.index"
end
end
If we run our spec again, our expectation for a successful response is now satisfied, but there’s a different failure:
$ bundle exec rspec spec/requests/books/index_spec.rb
GET /books
returns a list of books (FAILED - 1)
Failures:
1) GET /books returns a list of books
Failure/Error: expect(last_response.content_type).to eq("app/json; charset=utf-8")
expected: "app/json; charset=utf-8"
got: "app/octet-stream; charset=utf-8"
(compared using ==)
# ./spec/requests/books/index_spec.rb:7:in `block (2 levels) in <top (required)>'
Our response doesn’t have the expected format. Let’s adjust our action to return a JSON formatted response using response.format = :json. We’ll also set the response body to what our test expects:
# app/actions/books/index.rb
module Bookshelf
module Actions
module Books
class Index < Bookshelf::Action
def handle(*, response)
books = [
{title: "Test Driven Development"},
{title: "Practical Object-Oriented Design in Ruby"}
]
response.format = :json
response.body = books.to_json
end
end
end
end
end
If we run our spec, it now passes!
$ bundle exec rspec spec/requests/books/index_spec.rb
GET /books
returns a list of books
Finished in 0.02378 seconds (files took 0.49411 seconds to load)
1 example, 0 failures
Persisting books
Of course, returning a static list of books is not particularly useful.
Let’s address this by retrieving books from a database.
Integrated support for persistence based on ROM is coming in Hanami's 2.2 release. For now, we can bring our own simple ROM configuration to allow us to store books in a database.
Adding persistence using ROM
Let’s add just enough ROM to get persistence working using Postgres.
First, add these gems to the Gemfile and run bundle install:
# Gemfile
gem "rom", "~> 5.3"
gem "rom-sql", "~> 3.6"
gem "pg"
group :test do
gem "database_cleaner-sequel"
end
If you do not have Postgres installed, you can install it using Homebrew, asdf or by following the installation instruction on the PostgreSQL website.
With Postgres running, create databases for development and test using PostgreSQL’s createdb command:
$ createdb bookshelf_development
$ createdb bookshelf_test
In Hanami, providers offer a mechanism for configuring and using dependencies, like databases, within your app.
Copy and paste the following provider into a new file at config/providers/persistence.rb:
Hanami.app.register_provider :persistence, namespace: true do
prepare do
require "rom"
config = ROM::Configuration.new(:sql, target["settings"].database_url)
register "config", config
register "db", config.gateways[:default].connection
end
start do
config = target["persistence.config"]
config.auto_registration(
target.root.join("lib/bookshelf/persistence"),
namespace: "Bookshelf::Persistence"
)
register "rom", ROM.container(config)
end
end
For this persistence provider to function, we need to establish a database_url setting.
Settings in Hanami are defined by a Settings class in config/settings.rb:
# config/settings.rb
module Bookshelf
class Settings < Hanami::Settings
# Define your app settings here, for example:
#
# setting :my_flag, default: false, constructor: Types::Params::Bool
end
end
Settings can be strings, booleans, integers and other types. Each setting can be either optional or required (meaning the app won’t boot without them), and each can also have a default.
Each setting is sourced from an environment variable matching its name. For example my_flag will be sourced from ENV["MY_FLAG"].
You can read more about Hanami’s settings in the app guide.
Let’s add database_url and make it a required setting by using the Types::String constructor:
# config/settings.rb
module Bookshelf
class Settings < Hanami::Settings
# Define your app settings here, for example:
#
# setting :my_flag, default: false, constructor: Types::Params::Bool
setting :database_url, constructor: Types::String
end
end
Our bookshelf app will now raise an invalid settings error when it boots, unless a DATABASE_URL environment variable is present.
In development and test environments, Hanami uses the dotenv gem to load environment variables from .env files.
We can now create .env and .env.test files in order to set database_url appropriately in development and test environments:
# .env
DATABASE_URL=postgres://postgres:postgres@localhost:5432/bookshelf_development
# .env.test
DATABASE_URL=postgres://postgres:postgres@localhost:5432/bookshelf_test
You might need to adjust these connection strings based on your local postgres configuration.
See Using dotenv to manage environment variables for recommendations on handling these files.
To confirm that the database_url setting is working as expected, you can run bundle exec hanami console to start a console, then call the database_url method on your app’s settings object.
$ bundle exec hanami console
bookshelf[development]> Hanami.app["settings"].database_url
=> "postgres://postgres:postgres@localhost:5432/bookshelf_development"
And in test:
$ HANAMI_ENV=test bundle exec hanami console
bookshelf[test]> Hanami.app["settings"].database_url
=> "postgres://postgres:postgres@localhost:5432/bookshelf_test"
To ensure the database is cleaned between tests, add the following to a spec/support/database_cleaner.rb file:
# spec/support/database_cleaner.rb
require "database_cleaner-sequel"
Hanami.app.prepare(:persistence)
DatabaseCleaner[:sequel, db: Hanami.app["persistence.db"]]
RSpec.configure do |config|
config.before(:suite) do
DatabaseCleaner.strategy = :transaction
DatabaseCleaner.clean_with(:truncation)
end
config.around(:each, type: :database) do |example|
DatabaseCleaner.cleaning do
example.run
end
end
end
And then append the following line to spec/spec_helper.rb:
require_relative "support/database_cleaner"
Finally, enable ROM’s rake tasks for database migrations by appending the following to the Rakefile:
# Rakefile
require "rom/sql/rake_task"
task :environment do
require_relative "config/app"
require "hanami/prepare"
end
namespace :db do
task setup: :environment do
Hanami.app.prepare(:persistence)
ROM::SQL::RakeSupport.env = Hanami.app["persistence.config"]
end
end
Hanami's 2.2 release will bring persistence as a first class feature, after which none of the above set up will be required.
Creating a books table
With persistence ready, we can now create a books table.
To create a migration run:
$ bundle exec rake db:create_migration[create_books]
If your shell is zsh you will need to escape the square brackets:
bundle exec rake db:create_migration\[create_books\]
Edit the migration file in order to create a books table with title and author columns and a primary key:
# db/migrate/20221113050928_create_books.rb
ROM::SQL.migration do
change do
create_table :books do
primary_key :id
column :title, :text, null: false
column :author, :text, null: false
end
end
end
Migrate both the development and test databases:
$ bundle exec rake db:migrate
$ HANAMI_ENV=test bundle exec rake db:migrate
Lastly, let’s add a ROM relation to allow our app to interact with our books table. Create the following file at lib/bookshelf/persistence/relations/books.rb:
# lib/bookshelf/persistence/relations/books.rb
module Bookshelf
module Persistence
module Relations
class Books < ROM::Relation[:sql]
schema(:books, infer: true)
end
end
end
end
Listing books
With our books table ready to go, let’s adapt our books index spec to expect an index of persisted books:
RSpec.describe "GET /books", type: [:request, :database] do
let(:books) { app["persistence.rom"].relations[:books] }
before do
books.insert(title: "Practical Object-Oriented Design in Ruby", author: "Sandi Metz")
books.insert(title: "Test Driven Development", author: "Kent Beck")
end
it "returns a list of books" do
get "/books"
expect(last_response).to be_successful
expect(last_response.content_type).to eq("app/json; charset=utf-8")
response_body = JSON.parse(last_response.body)
expect(response_body).to eq([
{ "title" => "Practical Object-Oriented Design in Ruby", "author" => "Sandi Metz" },
{ "title" => "Test Driven Development", "author" => "Kent Beck" }
])
end
end
To get this spec to pass, we’ll need to update our books index action to return books from the books relation.
To access the books relation within the action, we can use Hanami’s “Deps mixin”. Covered in detail in the container and components section of the Architecture guide, the Deps mixin gives each of your app’s components easy access to the other components it depends on to achieve its work. We’ll see this in more detail as these guides progress.
For now however, it’s enough to know that we can use include Deps["persistence.rom"] to make ROM available via a rom method within our action. The books relation is then available via rom.relations[:books].
To satisfy our spec, we need to meet a few requirements. Firstly, we want to render each book’s title and author, but not its id. Secondly we want to return books alphabetically by title. We can achieve these requirements using the select and order methods offered by the books relation:
module Bookshelf
module Actions
module Books
class Index < Bookshelf::Action
include Deps["persistence.rom"]
def handle(*, response)
books = rom.relations[:books]
.select(:title, :author)
.order(:title)
.to_a
response.format = :json
response.body = books.to_json
end
end
end
end
end
Accessing relations directly from actions is not a commonly recommended pattern. Instead, a rom repository should be used. Here, however, the repository is ommitted for brevity. Hanami's 2.2 release will offer repositories out of the box.
With this action in place, the spec passes once more:
$ bundle exec rspec spec/requests/books/index_spec.rb
GET /books
returns a list of books
Finished in 0.05765 seconds (files took 1.36 seconds to load)
1 example, 0 failures
Parameter validation
Of course, returning every book in the database when a visitor makes a request to /books is not going to be a good strategy for very long. Luckily ROM relations offer pagination support. Let’s add pagination with a default page size of 5:
# lib/bookshelf/persistence/relations/books.rb
module Bookshelf
module Persistence
module Relations
class Books < ROM::Relation[:sql]
schema(:books, infer: true)
use :pagination
per_page 5
end
end
end
end
This will enable our books index to accept page and per_page params.
Let’s add a request spec verifying pagination:
# spec/requests/books/index/pagination_spec.rb
RSpec.describe "GET /books pagination", type: [:request, :database] do
let(:books) { app["persistence.rom"].relations[:books] }
before do
10.times do |n|
books.insert(title: "Book #{n}", author: "Author #{n}")
end
end
context "given valid page and per_page params" do
it "returns the correct page of books" do
get "/books?page=1&per_page=3"
expect(last_response).to be_successful
response_body = JSON.parse(last_response.body)
expect(response_body).to eq([
{ "title" => "Book 0", "author" => "Author 0" },
{ "title" => "Book 1", "author" => "Author 1" },
{ "title" => "Book 2", "author" => "Author 2" }
])
end
end
end
In our action class, we can use the request object to extract the relevant params from the incoming request, which allows our spec to pass:
# app/actions/books/index.rb
module Bookshelf
module Actions
module Books
class Index < Bookshelf::Action
include Deps["persistence.rom"]
def handle(request, response)
books = rom.relations[:books]
.select(:title, :author)
.order(:title)
.page(request.params[:page] || 1)
.per_page(request.params[:per_page] || 5)
.to_a
response.format = :json
response.body = books.to_json
end
end
end
end
end
Accepting parameters from the internet without validation is never a good idea however. Hanami actions offer built-in parameter validation, which we can use here to ensure that both page and per_page are positive integers, and that per_page is at most 100:
# app/actions/books/index.rb
module Bookshelf
module Actions
module Books
class Index < Bookshelf::Action
include Deps["persistence.rom"]
params do
optional(:page).value(:integer, gt?: 0)
optional(:per_page).value(:integer, gt?: 0, lteq?: 100)
end
def handle(request, response)
halt 422 unless request.params.valid?
books = rom.relations[:books]
.select(:title, :author)
.order(:title)
.page(request.params[:page] || 1)
.per_page(request.params[:per_page] || 5)
.to_a
response.format = :json
response.body = books.to_json
end
end
end
end
end
In this instance, the params block specifies the following:
pageandper_pageare optional parameters- if
pageis present, it must be an integer greater than 0 - if
per_pageis present, it must be an integer greater than 0 and less than or equal to 100
At the start of the handle method, the line halt 422 unless request.params.valid? ensures that the action halts and returns 422 Unprocessable if an invalid parameter was given.
A helpful response revealing why parameter validation failed can also be rendered by passing a body when calling halt:
halt 422, {errors: request.params.errors}.to_json unless request.params.valid?
# spec/requests/books/index/pagination_spec.rb
context "given invalid page and per_page params" do
it "returns a 422 unprocessable response" do
get "/books?page=-1&per_page=3000"
expect(last_response).to be_unprocessable
response_body = JSON.parse(last_response.body)
expect(response_body).to eq(
"errors" => {
"page" => ["must be greater than 0"],
"per_page" => ["must be less than or equal to 100"]
}
)
end
end
Validating parameters in actions is useful for performing parameter coercion and type validation. More complex domain-specific validations, or validations concerned with things such as uniqueness, however, are usually better performed at layers deeper than your HTTP actions.
You can find more details on actions and parameter validation in the Actions guide.
Showing a book
In addition to our books index, we also want to provide an endpoint for viewing the details of a particular book.
Let’s specify a /books/:id request that renders a book for a given id, or returns 404 if there’s no book with the provided id.
# spec/requests/books/show_spec.rb
RSpec.describe "GET /books/:id", type: [:request, :database] do
let(:books) { app["persistence.rom"].relations[:books] }
context "when a book matches the given id" do
let!(:book_id) do
books.insert(title: "Test Driven Development", author: "Kent Beck")
end
it "renders the book" do
get "/books/#{book_id}"
expect(last_response).to be_successful
expect(last_response.content_type).to eq("app/json; charset=utf-8")
response_body = JSON.parse(last_response.body)
expect(response_body).to eq(
"id" => book_id, "title" => "Test Driven Development", "author" => "Kent Beck"
)
end
end
context "when no book matches the given id" do
it "returns not found" do
get "/books/#{books.max(:id).to_i + 1}"
expect(last_response).to be_not_found
expect(last_response.content_type).to eq("app/json; charset=utf-8")
response_body = JSON.parse(last_response.body)
expect(response_body).to eq(
"error" => "not_found"
)
end
end
end
Because there’s no matching route yet, this spec immediately fails:
$ bundle exec rspec spec/requests/books/show_spec.rb
GET /books/:id
when a book matches the given id
renders the book (FAILED - 1)
when no book matches the given id
returns not found (FAILED - 2)
Failures:
1) GET /books/:id when a book matches the given id renders the book
Failure/Error: expect(last_response).to be_successful
expected `#<Rack::MockResponse:0x000000010c9f5788 @original_headers={"Content-Length"=>"9"}, @errors="", @cooki...ms/rack-2.2.4/lib/rack/response.rb:287>, @block=nil, @body=["Not Found"], @buffered=true, @length=9>.successful?` to be truthy, got false
# ./spec/requests/books/show_spec.rb:14:in `block (3 levels) in <top (required)>'
# ./spec/support/database_cleaner.rb:15:in `block (3 levels) in <top (required)>'
# ./spec/support/database_cleaner.rb:14:in `block (2 levels) in <top (required)>'
2) GET /books/:id when no book matches the given id returns not found
Failure/Error: expect(last_response.content_type).to eq("app/json; charset=utf-8")
expected: "app/json; charset=utf-8"
got: nil
(compared using ==)
# ./spec/requests/books/show_spec.rb:30:in `block (3 levels) in <top (required)>'
# ./spec/support/database_cleaner.rb:15:in `block (3 levels) in <top (required)>'
# ./spec/support/database_cleaner.rb:14:in `block (2 levels) in <top (required)>'
Finished in 0.05427 seconds (files took 0.88631 seconds to load)
2 examples, 2 failures
We can use Hanami’s action generator to create both a route and an action. Run:
$ bundle exec hanami generate action books.show --skip-view
If you inspect config/routes.rb you will see the generator has automatically added a new get "/books/:id", to: "books.show" route:
# config/routes.rb
module Bookshelf
class Routes < Hanami::Routes
root to: "home.index"
get "/books", to: "books.index"
get "/books/:id", to: "books.show"
end
end
We can now edit the new action at app/actions/books/show.rb to add the required behaviour. Here, we use param validation to coerce params[:id] to an integer, render a book if there’s one with a matching primary key, or return a 404 response. With this, our test passes.
# app/actions/books/show.rb
module Bookshelf
module Actions
module Books
class Show < Bookshelf::Action
include Deps["persistence.rom"]
params do
required(:id).value(:integer)
end
def handle(request, response)
book = rom.relations[:books].by_pk(
request.params[:id]
).one
response.format = :json
if book
response.body = book.to_json
else
response.status = 404
response.body = {error: "not_found"}.to_json
end
end
end
end
end
end
In addition to the #one method, which will return nil if there’s no book with the requisite id, ROM relations also provide a #one! method, which instead raises a ROM::TupleCountMismatchError exception when no record is found.
We can use this to handle 404s via Hanami’s action exception handling: config.handle_exception. This action configuration takes the name of a method to invoke when a particular exception occurs.
Taking this approach allows our handle method to concern itself only with the happy path:
# app/actions/books/show.rb
require "rom"
module Bookshelf
module Actions
module Books
class Show < Bookshelf::Action
include Deps["persistence.rom"]
config.handle_exception ROM::TupleCountMismatchError => :handle_not_found
params do
required(:id).value(:integer)
end
def handle(request, response)
book = rom.relations[:books].by_pk(
request.params[:id]
).one!
response.format = :json
response.body = book.to_json
end
private
def handle_not_found(_request, response, _exception)
response.status = 404
response.format = :json
response.body = {error: "not_found"}.to_json
end
end
end
end
end
This exception handling behaviour can also be moved into the base Bookshelf::Action class at app/action.rb, meaning that any action inheriting from Bookshelf::Action will handle ROM::TupleCountMismatchError in the same way.
# app/action.rb
# auto_register: false
require "hanami/action"
module Bookshelf
class Action < Hanami::Action
config.handle_exception ROM::TupleCountMismatchError => :handle_not_found
private
def handle_not_found(_request, response, _exception)
response.status = 404
response.format = :json
response.body = {error: "not_found"}.to_json
end
end
end
With its base action configured to handle ROM::TupleCountMismatchError exceptions, the Books::Show action can now be as follows and our spec continues to pass:
# app/actions/books/show.rb
module Bookshelf
module Actions
module Books
class Show < Bookshelf::Action
include Deps["persistence.rom"]
params do
required(:id).value(:integer)
end
def handle(request, response)
book = rom.relations[:books].by_pk(
request.params[:id]
).one!
response.format = :json
response.body = book.to_json
end
end
end
end
end
$ bundle exec rspec spec/requests/books/show_spec.rb
GET /books/:id
when a book matches the given id
renders the book
when no book matches the given id
returns not found
Finished in 0.07726 seconds (files took 1.29 seconds to load)
2 examples, 0 failures
Creating a book
Now that our visitors can list and view books, let’s allow them to create books too.
Here’s a spec for POST requests to the /books path, where it’s expected that only valid requests result in a book being created:
# spec/requests/books/create_spec.rb
RSpec.describe "POST /books", type: [:request, :database] do
let(:request_headers) do
{"HTTP_ACCEPT" => "app/json", "CONTENT_TYPE" => "app/json"}
end
context "given valid params" do
let(:params) do
{book: {title: "Practical Object-Oriented Design in Ruby", author: "Sandi Metz"}}
end
it "creates a book" do
post "/books", params.to_json, request_headers
expect(last_response).to be_created
end
end
context "given invalid params" do
let(:params) do
{book: {title: nil}}
end
it "returns 422 unprocessable" do
post "/books", params.to_json, request_headers
expect(last_response).to be_unprocessable
end
end
end
Executing this spec, we get the message Method Not Allowed, because there’s no route or action for handling this request.
Hanami’s action generator can add these for us:
$ bundle exec hanami generate action books.create --skip-view
The app’s routes now include the expected route - invoking the books.create action for POST requests to /books:
module Bookshelf
class Routes < Hanami::Routes
root to: "home.index"
get "/books", to: "books.index"
get "/books/:id", to: "books.show"
post "/books", to: "books.create"
end
end
And Hanami has generated an action at app/actions/books/create.rb:
# app/actions/books/create.rb
module Bookshelf
module Actions
module Books
class Create < Bookshelf::Action
def handle(*, response)
response.body = self.class.name
end
end
end
end
end
To enable convenient parsing of params from JSON request bodies, Hanami includes a body parser middleware that can be enabled through a config option on the app class. Enable it by adding the following to the Bookshelf::App class in config/app.rb:
# config/app.rb
require "hanami"
module Bookshelf
class App < Hanami::App
config.middleware.use :body_parser, :json
end
end
With this parser in place, the book key from the JSON body will be available in the action via request.params[:book].
We can now complete our create action by inserting a record into the books relation if the posted params are valid:
module Bookshelf
module Actions
module Books
class Create < Bookshelf::Action
include Deps["persistence.rom"]
params do
required(:book).hash do
required(:title).filled(:string)
required(:author).filled(:string)
end
end
def handle(request, response)
if request.params.valid?
book = rom.relations[:books].changeset(:create, request.params[:book]).commit
response.status = 201
response.body = book.to_json
else
response.status = 422
response.format = :json
response.body = request.params.errors.to_json
end
end
end
end
end
end
Our request spec now passes!
$ bundle exec rspec spec/requests/books/create_spec.rb
POST /books
given valid params
creates a book
given invalid params
returns 422 unprocessable
Finished in 0.07143 seconds (files took 1.32 seconds to load)
2 examples, 0 failures
In addition to validating title and author are present, the params block in the action also serves to prevent mass assignment - params not included in the schema (for example an attempt to inject a price of 0) will be discarded.
What’s next
So far we’ve seen how to create a new Hanami app, explored some of the basics of how an app is structured, and seen how we can list, display and create a simple book entity while validating user input.
Still, we’ve barely touched the surface of what Hanami offers.
From here you might want to look in more detail at routing and actions, or explore Hanami’s app architecture, starting with its component management and dependency injection systems.