Metaprogramming instance methods - something wrong with the syntax?

Question

NAMES = ['orange', 'pear']

  Fruit.class_eval do
    NAMES.each do |n|
        define_method "is_#{n}?" do
          self.name == Fruit.find_by_name(n)
        end
    end
  end

For a fruit object, I want to be able to explicitly ask whether it's an orange or not, for example, by the fruit object's name attribute. When I call Fruit.find_by_name('orange').is_orange? I get false. What am I doing wrong?

You can easily verify that your method is being invoked. As such, it's not the metaprogramming that is at fault, but your logic within the method. Check your ActiveRecord(?) thinking — Phrogz
– Phrogz, Commented Feb 6, 2011 at 15:34

Robin · Accepted Answer · 2011-02-06 15:37:16Z

1

self.name == Fruit.find_by_name(n)

seems wrong to me. Shouldnt you check

self.name == n

??

And you should indeed use instance_eval.

Also, I think it would be more ruby-like to name your method orange? instead of is_orange?.

edited Feb 6, 2011 at 15:37

answered Feb 6, 2011 at 15:29

Robin

22k10 gold badges66 silver badges87 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

tokland Over a year ago

ok, instance_eval makes sense for the question asked, but wouldn't it make even more sense to simply define those methods inside the class?

Collectives™ on Stack Overflow

Metaprogramming instance methods - something wrong with the syntax?

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related