mattr_accessor inside a class

rubyonrails-talk
1

Rails extends Ruby with mattr_accessor (Module accessor). As Ruby's attr_accessor generates getter/setter methods for instances, mattr_accessor provide getter/setter methods at the module level. In below example, you see that mattr_accessor declared in the class context of LookupContext. It's declared in class, not module. However, modules are defined in LookupContext, for example, the module ViewPaths, which makes use of the accessor. So is it safe to say that if a module accessor is declared in class, then it can only be available to modules of that class?

  class LookupContext     mattr_accessor :fallbacks     module ViewPaths       self.class.fallbacks.each do |resolver|

2

it looks as if it is onyl available on the class because if you look it says self.class.fallbacks, yet that wouldnt make sense either because then what would be the point of its existance if you had to reach the class for it it, why not just create a class level macro instead?

3

John Merlino wrote in post #1075232:

Rails extends Ruby with mattr_accessor (Module accessor). As Ruby's attr_accessor generates getter/setter methods for instances, mattr_accessor provide getter/setter methods at the module level. In below example, you see that mattr_accessor declared in the class context of LookupContext. It's declared in class, not module.

A class is a module.

However, modules are defined in LookupContext, for example, the module ViewPaths, which makes use of the accessor. So is it safe to say that if a module accessor is declared in class, then it can only be available to modules of that class?

What is 'it'?

class LookupContext   def LookupContext.fallbacks     @@fallbacks   end

  def LookupContext.fallbacks=(arr)     @@fallbacks = arr   end

  module ViewPaths     def ViewPaths.greet       p LookupContext.fallbacks     end   end end

class Dog   def bark     p LookupContext.fallbacks   end end

LookupContext.fallbacks = [10, 20, 30] p LookupContext.fallbacks

LookupContext::ViewPaths.greet Dog.new.bark

In this code:

module ViewPaths       self.class.fallbacks.each do |resolver|

...self is the module LookupContext::ViewPaths, and self.class is Module, and Module has no method 'fallbacks':

lass LookupContext   def LookupContext.fallbacks     @@fallbacks   end

  def LookupContext.fallbacks=(arr)     @@fallbacks = arr   end

  module ViewPaths     puts self     puts     puts self.class     puts     puts self.class.fallbacks   end end

--output:-- LookupContext::ViewPaths

Module

1.rb:60:in `<module:ViewPaths>': undefined method `fallbacks' for Module:Class (NoMethodError)   from 1.rb:57:in `<class:LookupContext>'   from 1.rb:48:in `<main>'