really simple example of has_many behavior

dumb_has_many_example.rb

#copy and paste into rails console to play

module DumbHasMany
  extend ActiveSupport::Concern

  module ClassMethods
    def has_many(method, args=nil)
      if args.nil? || !args.is_a?(Hash)
        type = method
      else
        type = initial_type = args.has_key?(:through) ? args[:through].to_s.downcase : method
        if args.has_key?(:to) || args.has_key?(:from)
          type = args.has_key?(:to) ? "#{self.name}##{initial_type}" : "#{args[:from]}##{initial_type}" 
        end
      end

      "method is #{method}, type is #{type}"
    end
  end
end

class Post
  include DumbHasMany
  def name
    "Post"
  end

end

class Student
  include DumbHasMany
  def name
    "Student"
  end

end

Post.has_many(:comments, through: :thoughts_about_stuff)
Post.has_many(:comments, from: Student)

a = Student.has_many(:comments, to: Post)
b = Post.has_many(:comments, from: Student)

a == b

a = Student.has_many(:comments, to: Post, through: :thoughts_about_stuff)
b = Post.has_many(:comments, from: Student, through: :thoughts_about_stuff)

a == b

Not sure I understand this:

Post.has_many(:comments, from: Student)

You would call post.comments and get Student objects?