From: Gavin Kistner <gavin.kistner@...>
Date: 2006-09-23T07:17:05+09:00
Subject: Re: Advice on using define_method in ActiveRecord descendant

>   for attr in [ :gross_receipts, :number_of_owners, 
> :annual_employee_payroll, :uninsured_subcontractors_contract_cost, 
> :insured_subcontractors_contract_cost ] do
>     self.class_eval do
>       define_method("#{attr.to_s}=(new_value)") {
>         write_attribute(attr, new_value.to_s.gsub(/,/, ''))
>       }
>     end
>   end

You're not defining the method quite correctly. You want the new_value
param to be an argument to the block.

class Foo
  [:bar, :jim, :jam].each{ |method_name|
    self.class_eval{
      define_method( "#{method_name}="){ |new_value|
        puts "The new value for '#{method_name}' is " + new_value.to_s
      }
    }
   }
end

f = Foo.new
f.bar = 42
#=> The new value for 'bar' is 42


Also, there's no reason to use #to_s inside string interpolation; it
happens automatically.