Rack

Rack 是什麼？

a Ruby Webserver Interface
Rack

Ruby 實作的網站伺服器介面。

規格

提供一個能夠回應 call 方法的物件，並且回傳一個包含以下三個元素的陣列：
1.HTTP 狀態（數字）
2.HTTP Header（Hash）
3.HTTP Body（陣列）

動起來！

$ mkdir rack_demo
$ cd rack_demo
$ rackup # ru = rackup

configuration /Users/emily/Desktop/Ruby_Bootcamp/rack-demo/config.ru not found

config.ru 檔案

run Proc.new {
  [
    200, # 狀態
    { "Content-Type" => "text/html" }, # HEAD
    ["Hello, rack"] # BODY
  ]
}

$ rack-demo rackup
Puma starting in single mode...
* Puma version: 5.6.5 (ruby 3.2.0-p0) ("Birdie's Version")
*  Min threads: 0
*  Max threads: 5
*  Environment: development
*          PID: 49301
* Listening on http://127.0.0.1:9292
* Listening on http://[::1]:9292
Use Ctrl-C to stop

只要有支援 call 方法的物件就行了

class Cat 
  def call(env)
    [
      200,
      { "Content-Type" => "text/html" },
      ["helle test test"]
    ]
  end
end

kitty = Cat.new

run kitty

中介軟體 Middleware

class Backdoor
  def initialize(app, whom = "no one")
    @app = app
    @whom = whom
  end

  def call(env)
    status, headers, body = @app.call(env)
    body << "<br />Powered by #{@whom}!"

    [status, headers, body]
  end
end

use Backdoor, "5xRuby"

run Proc.new {
  [200, { "Content-Type" => "text/html" }, ["Hello, Rack"]]
}

疊疊樂

use Backdoor, "Taipei" # 壓在最下面，但最後執行
use Backdoor, "Hello"
use Backdoor, "Kitty"


run Proc.new {
 [200, { "Content-Type" => "text/html" }, ["Hello, Rack"]]
}

關於 Ruby on Rails

Ruby on Rails 其實也是一種 Rack 應用程式

# This file is used by Rack-based servers to start the application.

require_relative 'config/environment'
run Rails.application # 會有一個 run 進入點

Rails 也掛了一大串的 middleware

$ rails middleware

use Webpacker::DevServerProxy
use ActionDispatch::HostAuthorization
use Rack::Sendfile
use ActionDispatch::Static
...略...
use Rack::Head
use Rack::ConditionalGet
use Rack::ETag
use Rack::TempfileReaper
run MyApp::Application.routes