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Diffstat (limited to 'guides/source/initialization.md')
| -rw-r--r-- | guides/source/initialization.md | 172 |
1 files changed, 128 insertions, 44 deletions
diff --git a/guides/source/initialization.md b/guides/source/initialization.md index c78eef5bf0..5e2e0ad3e3 100644 --- a/guides/source/initialization.md +++ b/guides/source/initialization.md @@ -29,9 +29,42 @@ quickly. Launch! ------- -Let's start to boot and initialize the app. It all begins with your app's -`bin/rails` executable. A Rails application is usually started by running -`rails console` or `rails server`. +Let's start to boot and initialize the app. A Rails application is usually +started by running `rails console` or `rails server`. + +### `railties/bin/rails` + +The `rails` in the command `rails server` is a ruby executable in your load +path. This executable contains the following lines: + +```ruby +version = ">= 0" +load Gem.bin_path('railties', 'rails', version) +``` + +If you try out this command in a Rails console, you would see that this loads +`railties/bin/rails`. A part of the file `railties/bin/rails.rb` has the +following code: + +```ruby +require "rails/cli" +``` + +The file `railties/lib/rails/cli` in turn calls +`Rails::AppRailsLoader.exec_app_rails`. + +### `railties/lib/rails/app_rails_loader.rb` + +The primary goal of the function `exec_app_rails` is to execute your app's +`bin/rails`. If the current directory does not have a `bin/rails`, it will +navigate upwards until it finds a `bin/rails` executable. Thus one can invoke a +`rails` command from anywhere inside a rails application. + +For `rails server` the equivalent of the following command is executed: + +```bash +$ exec ruby bin/rails server +``` ### `bin/rails` @@ -54,7 +87,7 @@ The `APP_PATH` constant will be used later in `rails/commands`. The `config/boot # Set up gems listed in the Gemfile. ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__) -require 'bundler/setup' if File.exists?(ENV['BUNDLE_GEMFILE']) +require 'bundler/setup' if File.exist?(ENV['BUNDLE_GEMFILE']) ``` In a standard Rails application, there's a `Gemfile` which declares all @@ -93,7 +126,9 @@ A standard Rails application depends on several gems, specifically: ### `rails/commands.rb` -Once `config/boot.rb` has finished, the next file that is required is `rails/commands` which will execute a command based on the arguments passed in. In this case, the `ARGV` array simply contains `server` which is extracted into the `command` variable using these lines: +Once `config/boot.rb` has finished, the next file that is required is +`rails/commands`, which helps in expanding aliases. In the current case, the +`ARGV` array simply contains `server` which will be passed over: ```ruby ARGV << '--help' if ARGV.empty? @@ -109,31 +144,64 @@ aliases = { command = ARGV.shift command = aliases[command] || command + +require 'rails/commands/commands_tasks' + +Rails::CommandsTasks.new(ARGV).run_command!(command) ``` TIP: As you can see, an empty ARGV list will make Rails show the help snippet. -If we used `s` rather than `server`, Rails will use the `aliases` defined in the file and match them to their respective commands. With the `server` command, Rails will run this code: +If we had used `s` rather than `server`, Rails would have used the `aliases` +defined here to find the matching command. + +### `rails/commands/command_tasks.rb` + +When one types an incorrect rails command, the `run_command` is responsible for +throwing an error message. If the command is valid, a method of the same name +is called. ```ruby -when 'server' - # Change to the application's path if there is no config.ru file in current directory. - # This allows us to run `rails server` from other directories, but still get - # the main config.ru and properly set the tmp directory. - Dir.chdir(File.expand_path('../../', APP_PATH)) unless File.exists?(File.expand_path("config.ru")) +COMMAND_WHITELIST = %(plugin generate destroy console server dbconsole application runner new version help) + +def run_command!(command) + if COMMAND_WHITELIST.include?(command) + send(command) + else + write_error_message(command) + end +end +``` + +With the `server` command, Rails will further run the following code: + +```ruby +def set_application_directory! + Dir.chdir(File.expand_path('../../', APP_PATH)) unless + File.exist?(File.expand_path("config.ru")) +end + +def server + set_application_directory! + require_command!("server") - require 'rails/commands/server' Rails::Server.new.tap do |server| - # We need to require application after the server sets environment, - # otherwise the --environment option given to the server won't propagate. require APP_PATH Dir.chdir(Rails.application.root) server.start end +end + +def require_command!(command) + require "rails/commands/#{command}" +end ``` -This file will change into the Rails root directory (a path two directories up from `APP_PATH` which points at `config/application.rb`), but only if the `config.ru` file isn't found. This then requires `rails/commands/server` which sets up the `Rails::Server` class. +This file will change into the Rails root directory (a path two directories up +from `APP_PATH` which points at `config/application.rb`), but only if the +`config.ru` file isn't found. This then requires `rails/commands/server` which +sets up the `Rails::Server` class. ```ruby require 'fileutils' @@ -217,12 +285,12 @@ With the `default_options` set to this: ```ruby def default_options { - :environment => ENV['RACK_ENV'] || "development", - :pid => nil, - :Port => 9292, - :Host => "0.0.0.0", - :AccessLog => [], - :config => "config.ru" + environment: ENV['RACK_ENV'] || "development", + pid: nil, + Port: 9292, + Host: "0.0.0.0", + AccessLog: [], + config: "config.ru" } end ``` @@ -261,37 +329,43 @@ and it's free for you to change based on your needs. ### `Rails::Server#start` -After `config/application` is loaded, `server.start` is called. This method is defined like this: +After `config/application` is loaded, `server.start` is called. This method is +defined like this: ```ruby def start - url = "#{options[:SSLEnable] ? 'https' : 'http'}://#{options[:Host]}:#{options[:Port]}" - puts "=> Booting #{ActiveSupport::Inflector.demodulize(server)}" - puts "=> Rails #{Rails.version} application starting in #{Rails.env} on #{url}" - puts "=> Run `rails server -h` for more startup options" + print_boot_information trap(:INT) { exit } - puts "=> Ctrl-C to shutdown server" unless options[:daemonize] + create_tmp_directories + log_to_stdout if options[:log_stdout] + + super + ... +end - #Create required tmp directories if not found - %w(cache pids sessions sockets).each do |dir_to_make| - FileUtils.mkdir_p(Rails.root.join('tmp', dir_to_make)) +private + + def print_boot_information + ... + puts "=> Run `rails server -h` for more startup options" + puts "=> Ctrl-C to shutdown server" unless options[:daemonize] + end + + def create_tmp_directories + %w(cache pids sessions sockets).each do |dir_to_make| + FileUtils.mkdir_p(File.join(Rails.root, 'tmp', dir_to_make)) + end end - unless options[:daemonize] + def log_to_stdout wrapped_app # touch the app so the logger is set up console = ActiveSupport::Logger.new($stdout) console.formatter = Rails.logger.formatter + console.level = Rails.logger.level Rails.logger.extend(ActiveSupport::Logger.broadcast(console)) end - - super -ensure - # The '-h' option calls exit before @options is set. - # If we call 'options' with it unset, we get double help banners. - puts 'Exiting' unless @options && options[:daemonize] -end ``` This is where the first output of the Rails initialization happens. This @@ -468,14 +542,24 @@ def initialize!(group=:default) #:nodoc: end ``` -As you can see, you can only initialize an app once. This is also where the initializers are run. +As you can see, you can only initialize an app once. The initializers are run through +the `run_initializers` method which is defined in `railties/lib/rails/initializable.rb` -TODO: review this +```ruby +def run_initializers(group=:default, *args) + return if instance_variable_defined?(:@ran) + initializers.tsort_each do |initializer| + initializer.run(*args) if initializer.belongs_to?(group) + end + @ran = true +end +``` -The initializers code itself is tricky. What Rails is doing here is it -traverses all the class ancestors looking for an `initializers` method, -sorting them and running them. For example, the `Engine` class will make -all the engines available by providing the `initializers` method. +The run_initializers code itself is tricky. What Rails is doing here is +traversing all the class ancestors looking for those that respond to an +`initializers` method. It then sorts the ancestors by name, and runs them. +For example, the `Engine` class will make all the engines available by +providing an `initializers` method on them. The `Rails::Application` class, as defined in `railties/lib/rails/application.rb` defines `bootstrap`, `railtie`, and `finisher` initializers. The `bootstrap` initializers |