What is the meaning of the class executable?

Question

The body of the class is executable, as in this code:

3.times do
  class C
    puts "hello"
  end
end

What is the meaning of this? I do not see the class value of the executable. Is it because we need code at the top level to execute, or can it return a value? If this is not the only reason, is there a good example to show that this is a brilliant idea?

Answer 1

For a few simple examples:

It allows you to work with attributes:

class Dog
  attr_reader :name
end

attr_reader, and others from this family are just methods that execute in the context where selfis the class object. They are not declarations; they actually execute as the class executes. So it depends on the ability of Ruby to call methods when defining a class.

:

class OptimisedClass
  if defined? JRUBY_VERSION
    def do_stuff
      jruby_optimised_stuff
    end
  else
    def stuff
      c_optimised_stuff
    end
  end
end

Answer 2

Ruby , . , if , . , , JRuby:

if RUBY_ENGINE == 'jruby'
  class SomeClass
  end
end

++ Java, , , #ifdefs. Ruby " ", Ruby .

ActiveRecord - Ruby ORM, , , .