Question

To set validation inside a Model in Rails, I should write something like:

class Post < ActiveRecord::Base
  validates :name,  :presence => true
  validates :title, :presence => true,
                    :length => { :minimum => 5 }
end

I can’t figure out how this works. It seems like it is calling a method named validates and is passing parameters, but this can’t be because, I believe I cannot call a method directly in a class body.

So what is actually happening in here?

update

From the answers it seems like this is calling a method from the inhereted Base class but then why does this not work?:

class Parent
  def foo
    puts "called foo"
  end
end

class Child < Parent
 foo
 foo
end

Answer 1

You wrote “but this can’t be because (I believe) you cannot call a method directly in a class body.”

But that’s not true — code is being executed as the class is loaded

Consider this:

class Hi
  puts "yo"
end

You’ll get:

yo
 => nil

the puts is executed when it’s loaded. So you can use this to create other methods or do whatever you need.