如何将局部变量从模块导入到 Ruby 中的另一个类

Question

I am new in Ruby.

I have a situation where I am generating some values at runtime in a module and I need to access it in another class. What is the best way to do it? Below I have given my directory structure and a dummy code. I want to import "local_variable_a" from module.rb into someclass.rb.

Directory Structure :

Folder_A -> Folder_B -> Folder_C -> module.rb

Folder_A -> Folder_D -> someclass.rb

module.rb

Module First
  Module Second
    def some_method
      local_variable_a = some_value
    end
  end
end    

someclass.rb

class Example
  def initialize(example)
    @example = example
  end

  def another_method
    local_variable_a = some_value  //import from module.rb
  end

Answer 1

Local variables in Ruby are just that. They are lexical variables that exist in the lexical scope (method, block, etc) where they are defined. As soon as that scope closes off they are garbage collected.

For example assigning the local variable here is completely pointless as its garbage collected as soon as the method finsishes:

def another_method
  local_variable_a = some_value  //import from module.rb
end

There is no variable importing feature in Ruby as its based around the use of methods for message passing. To "import" variables you pass them as input to methods - to "export" variables you return them from a method.

If you want a module to expose anything you would do it through a method:

module Foo
   # this is an instance variable that belongs to the module
  @baz = "Hello World"
  def self.bar
    @baz
  end
end

puts Foo.bar

If you want to have a module define a set of instance variables then just create an instance method that you call from your initializer:

module TimeStamps
  def set_timestamps!
    @initialized_at = Time.now
  end

  def initialized_at 
    @initialized_at
  end
end

class Bar
  include TimeStamps

  def initialize
    # ...
    set_timestamps!
  end
end

Bar.new.initialized_at
# => 2021-06-18 12:44:32.357627871 +0200