Ruby require include extend
很惭愧的说, 今天才稍稍理解了这几个加载的区别.
require
puts $LOAD_PATH
puts "----------------"
require 'active_model'
puts $LOAD_PATH
全局变量 $LOAD_PATH 顾名思义, 就是 Ruby 的加载路径. Ruby 只会在这些路径下查找.
/Users/focus/.rvm/gems/ruby-2.4.1@global/gems/did_you_mean-1.1.0/lib
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/x86_64-darwin17
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/vendor_ruby/2.4.0
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/vendor_ruby/2.4.0/x86_64-darwin17
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/vendor_ruby
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/2.4.0
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/2.4.0/x86_64-darwin17
----------------
/Users/focus/.rvm/gems/ruby-2.4.1@global/gems/did_you_mean-1.1.0/lib
/Users/focus/.rvm/gems/ruby-2.4.1/gems/concurrent-ruby-1.0.5/lib
/Users/focus/.rvm/gems/ruby-2.4.1/gems/activesupport-5.1.6/lib
/Users/focus/.rvm/gems/ruby-2.4.1/gems/activemodel-5.1.6/lib
/Users/focus/.rvm/gems/ruby-2.4.1/gems/i18n-1.0.1/lib
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby/2.4.0/x86_64-darwin17
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/site_ruby
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/vendor_ruby/2.4.0
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/vendor_ruby/2.4.0/x86_64-darwin17
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/vendor_ruby
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/2.4.0
/Users/focus/.rvm/rubies/ruby-2.4.1/lib/ruby/2.4.0/x86_64-darwin17
在启动解释器的时候可以用 -I=/your_path/ 的参数把自定义的路径加到 Ruby 的 $LOADPATH 中.
ruby -I=/Users/focus/Coding/ main.rb
以下是官网的翻译:
http://ruby-doc.org/core-2.5.0/Kernel.html#method-i-require
require(name) -> true or false
加载name, 如果成功返回
true, 如果已经加载就返回false. 如果文件名不是绝对路径, 就从$LOADPATH($:) 所列出的路径下查找. 如果文件扩展名是.rb, 就作为源文件加载; 如果扩展名是.so.o.dll或者当前平台上其他的默认共享库扩展, Ruby 会把他们当做 Ruby 扩展来加载. 如果没有扩展名, Ruby 会试图自动添加.rb.so等等 的扩展名然后再加载. 如果找不到就抛LoadError的异常.
For Ruby extensions the filename given may use any shared library extension. For example, on Linux the socket extension is “socket.so” and require ‘socket.dll’ will load the socket extension.
已经加载文件的绝对路径被添加到
$LOADED_FEATURES中 ($"), 不会重复加载同一个文件. 比如,require 'a'之后, 不会重复加载require './a'. 被加载的源文件中的所有常量和全局变量, 在被调用程序的全局空间上可用. 但是局部变量不会被传播到加载环境中.
require 不是关键字, 是方法.
在 Ruby 1.8 時代，Ruby 的 require 就是普通的 require，在 Ruby 1.9 之後，require 的事情則是交給 rubygems 套件來管理
include 和 extend
他们的作用是把模块里的方法加到当前模块/类上.
include 将目标方法加入到当前位置(一般作为实例方法), extend 将目标方法加入到当前位置之上(一般作为类方法).
module Tool
def say
puts "say hi."
end
end
class C1
# 将 Tool 中的方法加入到 C1 内, 作为实例方法
include Tool
end
C1.new.say
class C2
# 将 Tool 中的方法加入到 C2 上, 作为类方法
extend Tool
end
C2.say
include 是定义在 Module 上的方法;
extend 是定义在 Object 上的方法.
Hook
module MM
def hi
puts "MM"
end
end
module M
def self.included(base)
puts "#{base} has been included"
end
def self.extended(base)
base.extend MM
puts "#{base} has been extended"
end
end
class C
include M
extend M
def hello
puts "this is C instance"
end
end
C.hi
使用模块内的子模块来分发实例方法和类方法
module M
module M_to_include
def hi
"hi of M_to_include "
end
end
module M_to_extend
def hi
"hi of M_to_extend"
end
end
def self.included(base)
base.include M_to_include
base.extend M_to_extend
end
end
class C
include M
end
puts C.new.hi
# hi of M_to_include
puts C.hi
# hi of M_to_extend
扩展阅读
https://kaochenlong.com/2016/05/01/require/
https://ruby-china.org/topics/35350
https://ruby-china.org/topics/26038
https://ruby-china.org/topics/26037