define_method: How to dynamically create methods with arguments

Question

I want to create a bunch of methods for a find_by feature. I don\'t want to write the same thing over and over again so I want to use metaprogramming.

Say I want to

Answer 1

When you do this: define_method("self.find_by_#{attribute}")

that is incorrect. The argument to define_method is a symbol with a single word.

Let me show you some correct code, hopefully this will be clear:

class MyClass < ActiveRecord::Base
  ["name", "brand"].each do |attribute|
    define_method(:"find_by_#{attribute}") do |attr_|
      first(attribute.to_sym => attr_)
    end
  end
end

This will produce class methods for find_by_brand and find_by_name.

Note that if you're looking into metaprogramming, this is a good use-case for method_missing. here's a tutorial to use method_missing to implement the same functionality you're going for (find_by_)