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Hanami::Controller

Complete, fast, and testable actions for Rack and Hanami

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Installation

Add this line to your application's Gemfile:

gem "hanami-controller"

And then execute:

$ bundle

Or install it yourself as:

$ gem install hanami-controller

Usage

Hanami::Controller is a micro library for web frameworks. It works beautifully with Hanami::Router, but it can be employed everywhere. It's designed to be fast and testable.

Actions

The core of this framework are the actions. They are the endpoints that respond to incoming HTTP requests.

class Show < Hanami::Action
 def handle(request, response)
 response[:article] = ArticleRepository.new.find(request.params[:id])
 end
end

Hanami::Action follows the Hanami philosophy: a single purpose object with a minimal interface.

In this case, Hanami::Action provides the key public interface of #call(env), making your actions Rack-compatible. To provide custom behaviour when your actions are being called, you can implement #handle(request, response)

An action is an object and you have full control over it. In other words, you have the freedom to instantiate, inject dependencies and test it, both at the unit and integration level.

In the example below, the default repository is ArticleRepository. During a unit test we can inject a stubbed version, and invoke #call with the params. We're avoiding HTTP calls, we're also going to avoid hitting the database (it depends on the stubbed repository), we're just dealing with message passing. Imagine how fast the unit test could be.

class Show < Hanami::Action
 def initialize(configuration:, repository: ArticleRepository.new)
 @repository = repository
 super(configuration: configuration)
 end
 def handle(request, response)
 response[:article] = repository.find(request.params[:id])
 end
 private
 attr_reader :repository
end
configuration = Hanami::Controller::Configuration.new
action = Show.new(configuration: configuration, repository: ArticleRepository.new)
action.call(id: 23)

Params

The request params are part of the request passed as an argument to the #handle method. If routed with Hanami::Router, it extracts the relevant bits from the Rack env (e.g. the requested :id). Otherwise everything is passed as is: the full Rack env in production, and the given Hash for unit tests.

With Hanami::Router:

class Show < Hanami::Action
 def handle(request, *)
 # ...
 puts request.params # => { id: 23 } extracted from Rack env
 end
end

Standalone:

class Show < Hanami::Action
 def handle(request, *)
 # ...
 puts request.params # => { :"rack.version"=>[1, 2], :"rack.input"=>#<StringIO:0x007fa563463948>, ... }
 end
end

Unit Testing:

class Show < Hanami::Action
 def handle(request, *)
 # ...
 puts request.params # => { id: 23, key: "value" } passed as it is from testing
 end
end
action = Show.new(configuration: configuration)
response = action.call(id: 23, key: "value")

Allowlisting

Params represent an untrusted input. For security reasons it's recommended to allowlist them.

require "hanami/validations"
require "hanami/controller"
class Signup < Hanami::Action
 params do
 required(:first_name).filled(:str?)
 required(:last_name).filled(:str?)
 required(:email).filled(:str?)
 required(:address).schema do
 required(:line_one).filled(:str?)
 required(:state).filled(:str?)
 required(:country).filled(:str?)
 end
 end
 def handle(request, *)
 # Describe inheritance hierarchy
 puts request.params.class # => Signup::Params
 puts request.params.class.superclass # => Hanami::Action::Params
 # Allowlist :first_name, but not :admin
 puts request.params[:first_name] # => "Luca"
 puts request.params[:admin] # => nil
 # Allowlist nested params [:address][:line_one], not [:address][:line_two]
 puts request.params[:address][:line_one] # => "69 Tender St"
 puts request.params[:address][:line_two] # => nil
 end
end

Validations & Coercions

Because params are a well defined set of data required to fulfill a feature in your application, you can validate them. So you can avoid hitting lower MVC layers when params are invalid.

If you specify the :type option, the param will be coerced.

require "hanami/validations"
require "hanami/controller"
class Signup < Hanami::Action
 MEGABYTE = 1024 ** 2
 params do
 required(:first_name).filled(:str?)
 required(:last_name).filled(:str?)
 required(:email).filled?(:str?, format?: /\A.+@.+\z/)
 required(:password).filled(:str?).confirmation
 required(:terms_of_service).filled(:bool?)
 required(:age).filled(:int?, included_in?: 18..99)
 optional(:avatar).filled(size?: 1..(MEGABYTE * 3))
 end
 def handle(request, *)
 halt 400 unless request.params.valid?
 # ...
 end
end

Response

The output of #call is a Hanami::Action::Response:

class Show < Hanami::Action
end
action = Show.new(configuration: configuration)
action.call({}) # => #<Hanami::Action::Response:0x00007fe8be968418 @status=200 ...>

This is the same response object passed to #handle, where you can use its accessors to explicitly set status, headers, and body:

class Show < Hanami::Action
 def handle(*, response)
 response.status = 201
 response.body = "Hi!"
 response.headers.merge!("X-Custom" => "OK")
 end
end
action = Show.new
action.call({}) # => [201, { "X-Custom" => "OK" }, ["Hi!"]]

Exposures

In case you need to send data from the action to other layers of your application, you can use exposures. By default, an action exposes the received params.

class Show < Hanami::Action
 def handle(request, response)
 response[:article] = ArticleRepository.new.find(request.params[:id])
 end
end
action = Show.new(configuration: configuration)
response = action.call(id: 23)
article = response[:article]
article.class # => Article
article.id # => 23
response.exposures.keys # => [:params, :article]

Callbacks

If you need to execute logic before or after #handle is invoked, you can use callbacks. They are useful for shared logic like authentication checks.

class Show < Hanami::Action
 before :authenticate, :set_article
 def handle(*)
 end
 private
 def authenticate
 # ...
 end
 # `request` and `response` in the method signature is optional
 def set_article(request, response)
 response[:article] = ArticleRepository.new.find(request.params[:id])
 end
end

Callbacks can also be expressed as anonymous lambdas:

class Show < Hanami::Action
 before { ... } # do some authentication stuff
 before { |request, response| response[:article] = ArticleRepository.new.find(request.params[:id]) }
 def handle(*)
 end
end

Exceptions management

When the app raises an exception, hanami-controller, does NOT manage it. You can write custom exception handling on per action or configuration basis.

An exception handler can be a valid HTTP status code (eg. 500, 401), or a Symbol that represents an action method.

class Show < Hanami::Action
 handle_exception StandardError => 500
 def handle(*)
 raise
 end
end
action = Show.new(configuration: configuration)
action.call({}) # => [500, {}, ["Internal Server Error"]]

You can map a specific raised exception to a different HTTP status.

class Show < Hanami::Action
 handle_exception RecordNotFound => 404
 def handle(*)
 raise RecordNotFound
 end
end
action = Show.new(configuration: configuration)
action.call({}) # => [404, {}, ["Not Found"]]

You can also define custom handlers for exceptions.

class Create < Hanami::Action
 handle_exception ArgumentError => :my_custom_handler
 def handle(*)
 raise ArgumentError.new("Invalid arguments")
 end
 private
 def my_custom_handler(request, response, exception)
 response.status = 400
 response.body = exception.message
 end
end
action = Create.new(configuration: configuration)
action.call({}) # => [400, {}, ["Invalid arguments"]]

Exception policies can be defined globally via configuration:

configuration = Hanami::Controller::Configuration.new do |config|
 config.handle_exception RecordNotFound => 404
end
class Show < Hanami::Action
 def handle(*)
 raise RecordNotFound
 end
end
action = Show.new(configuration: configuration)
action.call({}) # => [404, {}, ["Not Found"]]

Inherited Exceptions

class MyCustomException < StandardError
end
module Articles
 class Index < Hanami::Action
 handle_exception MyCustomException => :handle_my_exception
 def handle(*)
 raise MyCustomException
 end
 private
 def handle_my_exception(request, response, exception)
 # ...
 end
 end
 class Show < Hanami::Action
 handle_exception StandardError => :handle_standard_error
 def handle(*)
 raise MyCustomException
 end
 private
 def handle_standard_error(request, response, exception)
 # ...
 end
 end
end
Articles::Index.new.call({}) # => `handle_my_exception` will be invoked
Articles::Show.new.call({}) # => `handle_standard_error` will be invoked,
 # because `MyCustomException` inherits from `StandardError`

Throwable HTTP statuses

When #halt is used with a valid HTTP code, it stops the execution and sets the proper status and body for the response:

class Show < Hanami::Action
 before :authenticate!
 def handle(*)
 # ...
 end
 private
 def authenticate!
 halt 401 unless authenticated?
 end
end
action = Show.new(configuration: configuration)
action.call({}) # => [401, {}, ["Unauthorized"]]

Alternatively, you can specify a custom message.

class Show < Hanami::Action
 def handle(request, response)
 response[:droid] = DroidRepository.new.find(request.params[:id]) or not_found
 end
 private
 def not_found
 halt 404, "This is not the droid you're looking for"
 end
end
action = Show.new(configuration: configuration)
action.call({}) # => [404, {}, ["This is not the droid you're looking for"]]

Cookies

You can read the original cookies sent from the HTTP client via request.cookies. If you want to send cookies in the response, use response.cookies.

They are read as a Hash from Rack env:

require "hanami/controller"
require "hanami/action/cookies"
class ReadCookiesFromRackEnv < Hanami::Action
 include Hanami::Action::Cookies
 def handle(request, *)
 # ...
 request.cookies[:foo] # => "bar"
 end
end
action = ReadCookiesFromRackEnv.new(configuration: configuration)
action.call({"HTTP_COOKIE" => "foo=bar"})

They are set like a Hash:

require "hanami/controller"
require "hanami/action/cookies"
class SetCookies < Hanami::Action
 include Hanami::Action::Cookies
 def handle(*, response)
 # ...
 response.cookies[:foo] = "bar"
 end
end
action = SetCookies.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie" => "foo=bar"}, "..."]

They are removed by setting their value to nil:

require "hanami/controller"
require "hanami/action/cookies"
class RemoveCookies < Hanami::Action
 include Hanami::Action::Cookies
 def handle(*, response)
 # ...
 response.cookies[:foo] = nil
 end
end
action = RemoveCookies.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie" => "foo=; max-age=0; expires=1970年1月01日 00:00:00 -0000"}, "..."]

Default values can be set in configuration, but overridden case by case.

require "hanami/controller"
require "hanami/action/cookies"
configuration = Hanami::Controller::Configuration.new do |config|
 config.cookies(max_age: 300) # 5 minutes
end
class SetCookies < Hanami::Action
 include Hanami::Action::Cookies
 def handle(*, response)
 # ...
 response.cookies[:foo] = { value: "bar", max_age: 100 }
 end
end
action = SetCookies.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie" => "foo=bar; max-age=100;"}, "..."]

Sessions

Actions have builtin support for Rack sessions. Similarly to cookies, you can read the session sent by the HTTP client via request.session, and also manipulate it via response.session.

require "hanami/controller"
require "hanami/action/session"
class ReadSessionFromRackEnv < Hanami::Action
 include Hanami::Action::Session
 def handle(request, *)
 # ...
 request.session[:age] # => "35"
 end
end
action = ReadSessionFromRackEnv.new(configuration: configuration)
action.call({ "rack.session" => { "age" => "35" } })

Values can be set like a Hash:

require "hanami/controller"
require "hanami/action/session"
class SetSession < Hanami::Action
 include Hanami::Action::Session
 def handle(*, response)
 # ...
 response.session[:age] = 31
 end
end
action = SetSession.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie"=>"rack.session=..."}, "..."]

Values can be removed like a Hash:

require "hanami/controller"
require "hanami/action/session"
class RemoveSession < Hanami::Action
 include Hanami::Action::Session
 def handle(*, response)
 # ...
 response.session[:age] = nil
 end
end
action = RemoveSession.new(configuration: configuration)
action.call({}) # => [200, {"Set-Cookie"=>"rack.session=..."}, "..."] it removes that value from the session

While Hanami::Controller supports sessions natively, it's session store agnostic. You have to specify the session store in your Rack middleware configuration (eg config.ru).

use Rack::Session::Cookie, secret: SecureRandom.hex(64)
run Show.new(configuration: configuration)

HTTP Cache

Hanami::Controller sets your headers correctly according to RFC 2616 / 14.9 for more on standard cache control directives: http://tools.ietf.org/html/rfc2616#section-14.9.1

You can easily set the Cache-Control header for your actions:

require "hanami/controller"
require "hanami/action/cache"
class HttpCacheController < Hanami::Action
 include Hanami::Action::Cache
 cache_control :public, max_age: 600 # => Cache-Control: public, max-age=600
 def handle(*)
 # ...
 end
end

Expires header can be specified using expires method:

require "hanami/controller"
require "hanami/action/cache"
class HttpCacheController < Hanami::Action
 include Hanami::Action::Cache
 expires 60, :public, max_age: 600 # => Expires: 2014年8月03日 17:47:02 GMT, Cache-Control: public, max-age=600
 def handle(*)
 # ...
 end
end

Conditional Get

According to HTTP specification, conditional GETs provide a way for web servers to inform clients that the response to a GET request hasn't change since the last request returning a 304 (Not Modified) response.

Passing the HTTP_IF_NONE_MATCH (content identifier) or HTTP_IF_MODIFIED_SINCE (timestamp) headers allows the web server define if the client has a fresh version of a given resource.

You can easily take advantage of Conditional Get using #fresh method:

require "hanami/controller"
require "hanami/action/cache"
class ConditionalGetController < Hanami::Action
 include Hanami::Action::Cache
 def handle(*)
 # ...
 fresh etag: resource.cache_key
 # => halt 304 with header IfNoneMatch = resource.cache_key
 end
end

If resource.cache_key is equal to IfNoneMatch header, then hanami will halt 304.

An alternative to hashing based check, is the time based check:

require "hanami/controller"
require "hanami/action/cache"
class ConditionalGetController < Hanami::Action
 include Hanami::Action::Cache
 def handle(*)
 # ...
 fresh last_modified: resource.updated_at
 # => halt 304 with header IfModifiedSince = resource.updated_at.httpdate
 end
end

If resource.updated_at is equal to IfModifiedSince header, then hanami will halt 304.

Redirect

If you need to redirect the client to another resource, use response.redirect_to:

class Create < Hanami::Action
 def handle(*, response)
 # ...
 response.redirect_to "http://example.com/articles/23"
 end
end
action = Create.new(configuration: configuration)
action.call({ article: { title: "Hello" }}) # => [302, {"Location" => "/articles/23"}, ""]

You can also redirect with a custom status code:

class Create < Hanami::Action
 def handle(*, response)
 # ...
 response.redirect_to "http://example.com/articles/23", status: 301
 end
end
action = Create.new(configuration: configuration)
action.call({ article: { title: "Hello" }}) # => [301, {"Location" => "/articles/23"}, ""]

MIME Types

Hanami::Action automatically sets the Content-Type header, according to the request.

class Show < Hanami::Action
 def handle(*)
 end
end
action = Show.new(configuration: configuration)
response = action.call({ "HTTP_ACCEPT" => "*/*" }) # Content-Type "application/octet-stream"
response.format # :all
response = action.call({ "HTTP_ACCEPT" => "text/html" }) # Content-Type "text/html"
response.format # :html

However, you can force this value:

class Show < Hanami::Action
 def handle(*, response)
 # ...
 response.format = :json
 end
end
action = Show.new(configuration: configuration)
response = action.call({ "HTTP_ACCEPT" => "*/*" }) # Content-Type "application/json"
response.format # :json
response = action.call({ "HTTP_ACCEPT" => "text/html" }) # Content-Type "application/json"
response.format # :json

You can restrict the accepted MIME types:

class Show < Hanami::Action
 accept :html, :json
 def handle(*)
 # ...
 end
end
# When called with "*/*" => 200
# When called with "text/html" => 200
# When called with "application/json" => 200
# When called with "application/xml" => 415

You can check if the requested MIME type is accepted by the client.

class Show < Hanami::Action
 def handle(request, response)
 # ...
 # @_env["HTTP_ACCEPT"] # => "text/html,application/xhtml+xml,application/xml;q=0.9"
 request.accept?("text/html") # => true
 request.accept?("application/xml") # => true
 request.accept?("application/json") # => false
 response.format # :html
 # @_env["HTTP_ACCEPT"] # => "*/*"
 request.accept?("text/html") # => true
 request.accept?("application/xml") # => true
 request.accept?("application/json") # => true
 response.format # :html
 end
end

Hanami::Controller is shipped with an extensive list of the most common MIME types. Also, you can register your own:

configuration = Hanami::Controller::Configuration.new do |config|
 config.format custom: "application/custom"
end
class Index < Hanami::Action
 def handle(*)
 end
end
action = Index.new(configuration: configuration)
response = action.call({ "HTTP_ACCEPT" => "application/custom" }) # => Content-Type "application/custom"
response.format # => :custom
class Show < Hanami::Action
 def handle(*, response)
 # ...
 response.format = :custom
 end
end
action = Show.new(configuration: configuration)
response = action.call({ "HTTP_ACCEPT" => "*/*" }) # => Content-Type "application/custom"
response.format # => :custom

Streamed Responses

When the work to be done by the server takes time, it may be a good idea to stream your response. Here's an example of a streamed CSV.

configuration = Hanami::Controller::Configuration.new do |config|
 config.format csv: 'text/csv'
end
class Csv < Hanami::Action
 def handle(*, response)
 response.format = :csv
 response.body = Enumerator.new do |yielder|
 yielder << csv_header
 # Expensive operation is streamed as each line becomes available
 csv_body.each_line do |line|
 yielder << line
 end
 end
 end
end

Note:

  • In development, Hanami' code reloading needs to be disabled for streaming to work. This is because Shotgun interferes with the streaming action. You can disable it like this hanami server --code-reloading=false
  • Streaming does not work with WEBrick as it buffers its response. We recommend using puma, though you may find success with other servers

No rendering, please

Hanami::Controller is designed to be a pure HTTP endpoint, rendering belongs to other layers of MVC. You can set the body directly (see response), or use Hanami::View.

Controllers

A Controller is nothing more than a logical group of actions: just a Ruby module.

module Articles
 class Index < Hanami::Action
 # ...
 end
 class Show < Hanami::Action
 # ...
 end
end
Articles::Index.new(configuration: configuration).call({})

Hanami::Router integration

require "hanami/router"
require "hanami/controller"
module Web
 module Controllers
 module Books
 class Show < Hanami::Action
 def handle(*)
 end
 end
 end
 end
end
configuration = Hanami::Controller::Configuration.new
router = Hanami::Router.new(configuration: configuration, namespace: Web::Controllers) do
 get "/books/:id", "books#show"
end

Rack integration

Hanami::Controller is compatible with Rack. If you need to use any Rack middleware, please mount them in config.ru.

Configuration

Hanami::Controller can be configured via Hanami::Controller::Configuration. It supports a few options:

require "hanami/controller"
configuration = Hanami::Controller::Configuration.new do |config|
 # If the given exception is raised, return that HTTP status
 # It can be used multiple times
 # Argument: hash, empty by default
 #
 config.handle_exception ArgumentError => 404
 # Register a format to MIME type mapping
 # Argument: hash, key: format symbol, value: MIME type string, empty by default
 #
 config.format custom: "application/custom"
 # Define a default format to set as `Content-Type` header for response,
 # unless otherwise specified.
 # If not defined here, it will return Rack's default: `application/octet-stream`
 # Argument: symbol, it should be already known. defaults to `nil`
 #
 config.default_response_format = :html
 # Define a default charset to return in the `Content-Type` response header
 # If not defined here, it returns `utf-8`
 # Argument: string, defaults to `nil`
 #
 config.default_charset = "koi8-r"
end

Thread safety

An Action is immutable, it works without global state, so it's thread-safe by design.

Versioning

Hanami::Controller uses Semantic Versioning 2.0.0

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request

Copyright

Copyright © 2014–2024 Hanami Team – Released under MIT License

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Complete, fast and testable actions for Rack and Hanami

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