Comment by asattarmd | Hacker News Reader

Comment by asattarmd | Hacker News Reader

Parent Full thread

  class Blog < ActiveRecord::Base
  end

Ever wonder how that works? Metaprogramming.

  enum status: [ :active, :archived ].
  validates :status, presence: true

Ever wonder how that works? Metaprogramming.

Used the awesome debugger, pry? Ever wonder how that works? Metaprogramming.

`find_by_id` isn't the only thing that's implemented using Metaprogramming. Practically, everything within ActiveModel is achieved through Metaprogramming. It is one very important reason that allows Ruby to be so expressive.

You can expose the same functionality in, say, C# or F# if you want to give up static type checking. (Actually with F# type providers or a language with good macros, you can keep static analysis if you're willing to bind yourself to the database at build time.) This is just a use of dynamic binding. That's fine, I just thought there was more to it, something that requires a lack of static analysis, multi threading, etc.

Also, metaprogramming allows one to create find_by_id as a function at runtime after the first use of it, it becomes part of the class.

Reply on news.ycombinator.com