RAILS4 startup process

This post will take you through the sequence of code calls that use the Rails Server command to the application launch, describe the boot process for Rails server, a brief translation of rails guide and some bloggers, and please forgive me for the bad translation. Look at the time, it is best to find a copy of the source code of RAILS4 together against the view.

Original address: http://guides.ruby-china.org/initialization.html

When we use Rails C (onsole) or Rails s (erver) to start a rails application, rails s actually executes a ruby script under the current path:

Version = ">=0" Load Gem.bin_path (' railties ', ' rails ', version)

If you enter the above command in the Rails console, you will see that railties/bin/rails is executed.

In the last line of Railties/bin/rails source, you can see

Require "RAILS/CLI"

Require RAILTIES/LIB/RAILS/CLI, continue to follow up, in the RAILTIES/LIB/RAILS/CLI:

Require ' Rails/app_rails_loader ' # If We is inside a rails application This method performs an exec and thus# the rest of This script was not run. Rails::apprailsloader.exec_app_rails

Continue into railties/lib/rails/app_rails_loader.rb

ruby = gem.rubyexecutables = [' bin/rails ',  ' script/rails ']......class <<  self    ......    def exec_app_rails       original_cwd = Dir.pwd      loop do         if exe = find_executable           contents = file.read (EXE)                 if contents =~ /(APP| ENGINE) _path/            exec ruby, exe,  *ARGV            break # non  reachable, hack to be able to stub exec in the test  suite        &Nbsp; elsif exe.end_with? (' Bin/rails ')  && contents.include? (' This file was generated by bundler ')               $stderr. Puts (bundler_warning)              object.const_set (: App_path, file.expand_path (' config/application ',  Dir.pwd))             require file.expand_path ('.. /boot ',  app_path)             require  ' Rails/commands '             break           end        end         # if we exhaust the search there is  no executable, this could be a        # call to generate a new  application, so restore the original cwd.         dir.chdir (ORIGINAL_CWD)  and return if pathname.new (dir.pwd) .root?                # otherwise keep moving  upwards in search of an executable.         dir.chdir ('.. ')       end    end            def find_executable      executables.find {  |exe| file.file? (EXE)  }    endend

You can see from the above code that rails::apprailsloader.exec_app_rails will find Bin/rails or script/rails in the current directory, and it will execute:

exec Gem.ruby, bin/rails, *ARGV

That is equivalent to

EXEC Ruby Bin/rails Server

If there is no bin/rails or script/rails in the current directory, it will continue recursively up until the bin (script)/rails is found, so rails server or rails can be used anywhere in the rails project's root directory and subdirectories Console command

Bin/rails:

#!/usr/bin/env Rubyapp_path = File.expand_path ('.. /.. /config/application ', __file__) require_relative '. /config/boot ' Require ' rails/commands '

App_path constants will be used later in the Rails/commands ,require_relative '. /config/boot ' is require the config/boot.rb file, BOOT.RB is responsible for loading the boot bundler

Config/boot.rb

# Set up gems listed in the gemfile.env[' Bundle_gemfile ' | | = File.expand_path ('.. /.. /gemfile ', __file__) require ' bundler/setup ' if file.exist? (env[' Bundle_gemfile ')

In a standard rails application, the Gemfile file declares all application dependencies, env[' Bundle_gemfile '] stores gemfile file addresses, when gemfile files exist, goes back to require Bundle/setup, The path used for bundler configuration to load gemfile dependencies.

A standard rails application needs to rely on several gem packages, such as:

• Actionmailer

• Actionpack

• Actionview

• Activemodel

• ActiveRecord

• Activesupport

• Arel

• Builder

• Bundler

• Erubis

• i18n

• Mail

• Mime-types

• Polyglot

• Rack

• Rack-cache

• Rack-mount

• Rack-test

• Rails

• Railties

• Rake

• Sqlite3

• Thor

• Treetop

• Tzinfo

Require config/boot.rb back to bin/rails, and finally require rails/commands

Rails/commands.rb

Used primarily to extend the aliases of Rails command parameters:

Rails/commands.rb

ARGV << '--help ' if argv.empty? aliases = {"G" = "Generate", "D" = "Destroy", "c" = "console", "s" = "" Server "," db "=" = "Dbcon Sole "," r "=" Runner "} command = Argv.shiftcommand = Aliases[command] | | Command require ' rails/commands/commands_tasks ' rails::commandstasks.new (ARGV). run_command! (command)

You can see that when you do not pass arguments, it is actually equivalent to rails--help, and rails S is equivalent to the Rails server

Rails/commands/command_tasks.rb

When an incorrect rails command is entered, the Run_command method is responsible for throwing an error message. If the command is valid, the method with the same name is called

command_whitelist = % (plugin generate destroy console server dbconsole  APPLICATION RUNNER NEW VERSION HELP)  def run_command! (command)   command = parse_command (command)   if command_whitelist.include? (command)     send (command)   else    write_error_message ( command)   endenddef write_error_message (command)   puts  "Error: command   ' #{command} '  not recognized '   if %x{rake #{command} --dry-run 2 >&1 } && $?. success?    puts  "did you mean:  ' $ rake #{command} '  ?\n \ n "  end  write_help_message   exit (1) end           def parse_command (command)    case command    when  ' --version ',  '-V '       ' version '    when  '--help ',  '-h '        ' Help '   else     command    endend

Wait, go on.

RAILS4 startup process